MariaDB Server Documentation


MariaDB Knowledge Base

For any errors please see Bug Reporting

Document generated on: 2022-03-30

Chapter Contents

  1. Chapter 1 Using MariaDB Server 18
    1. 1.1 SQL Statements & Structure 18
    2. 1.2 Built-in Functions 675

Table of Contents

  1. Chapter 1 Using MariaDB Server 18
    1. 1.1 SQL Statements & Structure 18
      1. 1.1.1 SQL Statements 18
        1. 1.1.1.1 Account Management SQL Commands 19
          1. 1.1.1.1.1 CREATE USER 20
          2. 1.1.1.1.2 ALTER USER 26
          3. 1.1.1.1.3 DROP USER 29
          4. 1.1.1.1.4 GRANT 31
          5. 1.1.1.1.5 RENAME USER 40
          6. 1.1.1.1.6 REVOKE 41
          7. 1.1.1.1.7 SET PASSWORD 41
          8. 1.1.1.1.8 CREATE ROLE 43
          9. 1.1.1.1.9 DROP ROLE 44
          10. 1.1.1.1.10 SET ROLE 45
          11. 1.1.1.1.11 SET DEFAULT ROLE 46
          12. 1.1.1.1.12 SHOW GRANTS 47
          13. 1.1.1.1.13 SHOW CREATE USER 48
        2. 1.1.1.2 Administrative SQL Statements 48
          1. 1.1.1.2.1 Table Statements 49
            1. 1.1.1.2.1.1 ALTER 50
              1. 1.1.1.2.1.1.1 ALTER TABLE 51
              2. 1.1.1.2.1.1.2 ALTER DATABASE 62
              3. 1.1.1.2.1.1.3 ALTER EVENT 63
              4. 1.1.1.2.1.1.4 ALTER FUNCTION 64
              5. 1.1.1.2.1.1.5 ALTER LOGFILE GROUP 64
              6. 1.1.1.2.1.1.6 ALTER PROCEDURE 64
              7. 1.1.1.2.1.1.7 ALTER SEQUENCE 65
              8. 1.1.1.2.1.1.8 ALTER SERVER 65
              9. 1.1.1.2.1.1.9 ALTER TABLESPACE 65
              10. 1.1.1.2.1.1.10 ALTER USER 65
              11. 1.1.1.2.1.1.11 ALTER VIEW 65
            2. 1.1.1.2.1.2 ANALYZE TABLE 66
            3. 1.1.1.2.1.3 CHECK TABLE 67
            4. 1.1.1.2.1.4 CHECK VIEW 67
            5. 1.1.1.2.1.5 CHECKSUM TABLE 68
            6. 1.1.1.2.1.6 CREATE TABLE 69
            7. 1.1.1.2.1.7 DELETE 80
            8. 1.1.1.2.1.8 DROP TABLE 82
            9. 1.1.1.2.1.9 Installing System Tables (mysql_install_db) 84
            10. 1.1.1.2.1.10 mysqlcheck 84
            11. 1.1.1.2.1.11 OPTIMIZE TABLE 88
            12. 1.1.1.2.1.12 RENAME TABLE 89
            13. 1.1.1.2.1.13 REPAIR TABLE 90
            14. 1.1.1.2.1.14 REPAIR VIEW 90
            15. 1.1.1.2.1.15 REPLACE 91
            16. 1.1.1.2.1.16 SHOW COLUMNS 93
            17. 1.1.1.2.1.17 SHOW CREATE TABLE 95
            18. 1.1.1.2.1.18 SHOW INDEX 96
            19. 1.1.1.2.1.19 TRUNCATE TABLE 98
            20. 1.1.1.2.1.20 UPDATE 99
            21. 1.1.1.2.1.21 IGNORE 101
            22. 1.1.1.2.1.22 System-Versioned Tables 102
          2. 1.1.1.2.2 ANALYZE and EXPLAIN Statements 102
            1. 1.1.1.2.2.1 ANALYZE FORMAT=JSON 102
            2. 1.1.1.2.2.2 ANALYZE FORMAT=JSON Examples 103
            3. 1.1.1.2.2.3 ANALYZE Statement 103
            4. 1.1.1.2.2.4 EXPLAIN 105
            5. 1.1.1.2.2.5 EXPLAIN ANALYZE 109
            6. 1.1.1.2.2.6 EXPLAIN FORMAT=JSON 109
            7. 1.1.1.2.2.7 SHOW EXPLAIN 110
            8. 1.1.1.2.2.8 Using Buffer UPDATE Algorithm 111
          3. 1.1.1.2.3 BACKUP Commands 112
            1. 1.1.1.2.3.1 BACKUP STAGE 112
            2. 1.1.1.2.3.2 BACKUP LOCK 113
            3. 1.1.1.2.3.3 Mariabackup and BACKUP STAGE Commands 114
            4. 1.1.1.2.3.4 Storage Snapshots and BACKUP STAGE Commands 114
          4. 1.1.1.2.4 FLUSH Commands 115
            1. 1.1.1.2.4.1 FLUSH 115
            2. 1.1.1.2.4.2 FLUSH QUERY CACHE 119
            3. 1.1.1.2.4.3 FLUSH TABLES FOR EXPORT 119
          5. 1.1.1.2.5 Replication Commands 120
            1. 1.1.1.2.5.1 CHANGE MASTER TO 121
            2. 1.1.1.2.5.2 START SLAVE 131
            3. 1.1.1.2.5.3 STOP SLAVE 132
            4. 1.1.1.2.5.4 RESET SLAVE 133
            5. 1.1.1.2.5.5 SET GLOBAL SQL_SLAVE_SKIP_COUNTER 133
            6. 1.1.1.2.5.6 SHOW RELAYLOG EVENTS 134
            7. 1.1.1.2.5.7 SHOW SLAVE STATUS 135
            8. 1.1.1.2.5.8 SHOW MASTER STATUS 138
            9. 1.1.1.2.5.9 SHOW SLAVE HOSTS 139
            10. 1.1.1.2.5.10 RESET MASTER 140
          6. 1.1.1.2.6 Plugin SQL Statements 140
            1. 1.1.1.2.6.1 SHOW PLUGINS 140
            2. 1.1.1.2.6.2 SHOW PLUGINS SONAME 141
            3. 1.1.1.2.6.3 INSTALL PLUGIN 141
            4. 1.1.1.2.6.4 UNINSTALL PLUGIN 143
            5. 1.1.1.2.6.5 INSTALL SONAME 143
            6. 1.1.1.2.6.6 UNINSTALL SONAME 144
            7. 1.1.1.2.6.7 mysql_plugin 145
          7. 1.1.1.2.7 SET Commands 145
            1. 1.1.1.2.7.1 SET 146
            2. 1.1.1.2.7.2 SET CHARACTER SET 148
            3. 1.1.1.2.7.3 SET GLOBAL SQL_SLAVE_SKIP_COUNTER 149
            4. 1.1.1.2.7.4 SET NAMES 149
            5. 1.1.1.2.7.5 SET PASSWORD 150
            6. 1.1.1.2.7.6 SET ROLE 150
            7. 1.1.1.2.7.7 SET SQL_LOG_BIN 150
            8. 1.1.1.2.7.8 SET STATEMENT 151
            9. 1.1.1.2.7.9 SET TRANSACTION 152
            10. 1.1.1.2.7.10 SET Variable 153
          8. 1.1.1.2.8 SHOW 154
            1. 1.1.1.2.8.1 About SHOW 156
            2. 1.1.1.2.8.2 Extended Show 157
            3. 1.1.1.2.8.3 SHOW AUTHORS 158
            4. 1.1.1.2.8.4 SHOW BINARY LOGS 159
            5. 1.1.1.2.8.5 SHOW BINLOG EVENTS 159
            6. 1.1.1.2.8.6 SHOW CHARACTER SET 160
            7. 1.1.1.2.8.7 SHOW CLIENT_STATISTICS 161
            8. 1.1.1.2.8.8 SHOW COLUMNS 161
            9. 1.1.1.2.8.9 SHOW CONTRIBUTORS 161
            10. 1.1.1.2.8.10 SHOW CREATE DATABASE 162
            11. 1.1.1.2.8.11 SHOW CREATE EVENT 163
            12. 1.1.1.2.8.12 SHOW CREATE FUNCTION 163
            13. 1.1.1.2.8.13 SHOW CREATE PACKAGE 164
            14. 1.1.1.2.8.14 SHOW CREATE PACKAGE BODY 165
            15. 1.1.1.2.8.15 SHOW CREATE PROCEDURE 166
            16. 1.1.1.2.8.16 SHOW CREATE SEQUENCE 167
            17. 1.1.1.2.8.17 SHOW CREATE TABLE 168
            18. 1.1.1.2.8.18 SHOW CREATE TRIGGER 168
            19. 1.1.1.2.8.19 SHOW CREATE USER 168
            20. 1.1.1.2.8.20 SHOW CREATE VIEW 168
            21. 1.1.1.2.8.21 SHOW DATABASES 169
            22. 1.1.1.2.8.22 SHOW ENGINE 170
            23. 1.1.1.2.8.23 SHOW ENGINE INNODB STATUS 171
            24. 1.1.1.2.8.24 SHOW ENGINES 172
            25. 1.1.1.2.8.25 SHOW ERRORS 174
            26. 1.1.1.2.8.26 SHOW EVENTS 175
            27. 1.1.1.2.8.27 SHOW FUNCTION STATUS 176
            28. 1.1.1.2.8.28 SHOW GRANTS 176
            29. 1.1.1.2.8.29 SHOW INDEX 176
            30. 1.1.1.2.8.30 SHOW INDEX_STATISTICS 176
            31. 1.1.1.2.8.32 SHOW LOCALES 177
            32. 1.1.1.2.8.33 SHOW BINLOG STATUS 177
            33. 1.1.1.2.8.34 SHOW OPEN TABLES 177
            34. 1.1.1.2.8.35 SHOW PACKAGE BODY STATUS 178
            35. 1.1.1.2.8.36 SHOW PACKAGE STATUS 178
            36. 1.1.1.2.8.37 SHOW PLUGINS 179
            37. 1.1.1.2.8.38 SHOW PLUGINS SONAME 179
            38. 1.1.1.2.8.39 SHOW PRIVILEGES 179
            39. 1.1.1.2.8.40 SHOW PROCEDURE CODE 180
            40. 1.1.1.2.8.41 SHOW PROCEDURE STATUS 181
            41. 1.1.1.2.8.42 SHOW PROCESSLIST 182
            42. 1.1.1.2.8.43 SHOW PROFILES 182
            43. 1.1.1.2.8.44 SHOW QUERY_RESPONSE_TIME 183
            44. 1.1.1.2.8.45 SHOW RELAYLOG EVENTS 183
            45. 1.1.1.2.8.46 SHOW REPLICA HOSTS 183
            46. 1.1.1.2.8.47 SHOW REPLICA STATUS 183
            47. 1.1.1.2.8.48 SHOW STATUS 183
            48. 1.1.1.2.8.49 SHOW TABLE STATUS 189
            49. 1.1.1.2.8.50 SHOW TABLES 190
            50. 1.1.1.2.8.51 SHOW TABLE_STATISTICS 191
            51. 1.1.1.2.8.52 SHOW TRIGGERS 192
            52. 1.1.1.2.8.53 SHOW USER_STATISTICS 193
            53. 1.1.1.2.8.54 SHOW VARIABLES 194
            54. 1.1.1.2.8.55 SHOW WARNINGS 195
            55. 1.1.1.2.8.56 SHOW WSREP_MEMBERSHIP 197
            56. 1.1.1.2.8.57 SHOW WSREP_STATUS 197
          9. 1.1.1.2.9 System Tables 198
            1. 1.1.1.2.9.1 Information Schema 198
              1. 1.1.1.2.9.1.1 Information Schema Tables 198
                1. 1.1.1.2.9.1.1.1 Information Schema InnoDB Tables 201
                  1. 1.1.1.2.9.1.1.1.1 Information Schema INNODB_BUFFER_PAGE Table 202
                  2. 1.1.1.2.9.1.1.1.2 Information Schema INNODB_BUFFER_PAGE_LRU Table 203
                  3. 1.1.1.2.9.1.1.1.3 Information Schema INNODB_BUFFER_POOL_PAGES Table 204
                  4. 1.1.1.2.9.1.1.1.4 Information Schema INNODB_BUFFER_POOL_PAGES_BLOB Table 205
                  5. 1.1.1.2.9.1.1.1.5 Information Schema INNODB_BUFFER_POOL_PAGES_INDEX Table 205
                  6. 1.1.1.2.9.1.1.1.6 Information Schema INNODB_BUFFER_POOL_STATS Table 205
                  7. 1.1.1.2.9.1.1.1.7 Information Schema INNODB_CHANGED_PAGES Table 207
                  8. 1.1.1.2.9.1.1.1.8 Information Schema INNODB_CMP and INNODB_CMP_RESET Tables 207
                  9. 1.1.1.2.9.1.1.1.9 Information Schema INNODB_CMPMEM and INNODB_CMPMEM_RESET Tables 208
                  10. 1.1.1.2.9.1.1.1.10 Information Schema INNODB_CMP_PER_INDEX and INNODB_CMP_PER_INDEX_RESET Tables 208
                  11. 1.1.1.2.9.1.1.1.11 Information Schema INNODB_FT_BEING_DELETED Table 209
                  12. 1.1.1.2.9.1.1.1.12 Information Schema INNODB_FT_CONFIG Table 209
                  13. 1.1.1.2.9.1.1.1.13 Information Schema INNODB_FT_DEFAULT_STOPWORD Table 210
                  14. 1.1.1.2.9.1.1.1.14 Information Schema INNODB_FT_DELETED Table 210
                  15. 1.1.1.2.9.1.1.1.15 Information Schema INNODB_FT_INDEX_CACHE Table 211
                  16. 1.1.1.2.9.1.1.1.16 Information Schema INNODB_FT_INDEX_TABLE Table 212
                  17. 1.1.1.2.9.1.1.1.17 Information Schema INNODB_LOCK_WAITS Table 213
                  18. 1.1.1.2.9.1.1.1.18 Information Schema INNODB_LOCKS Table 213
                  19. 1.1.1.2.9.1.1.1.19 Information Schema INNODB_METRICS Table 214
                  20. 1.1.1.2.9.1.1.1.20 Information Schema INNODB_MUTEXES Table 221
                  21. 1.1.1.2.9.1.1.1.21 Information Schema INNODB_SYS_COLUMNS Table 221
                  22. 1.1.1.2.9.1.1.1.22 Information Schema INNODB_SYS_DATAFILES Table 222
                  23. 1.1.1.2.9.1.1.1.23 Information Schema INNODB_SYS_FIELDS Table 223
                  24. 1.1.1.2.9.1.1.1.24 Information Schema INNODB_SYS_FOREIGN Table 223
                  25. 1.1.1.2.9.1.1.1.25 Information Schema INNODB_SYS_FOREIGN_COLS Table 223
                  26. 1.1.1.2.9.1.1.1.26 Information Schema INNODB_SYS_INDEXES Table 224
                  27. 1.1.1.2.9.1.1.1.27 Information Schema INNODB_SYS_SEMAPHORE_WAITS Table 224
                  28. 1.1.1.2.9.1.1.1.28 Information Schema INNODB_SYS_TABLES Table 225
                  29. 1.1.1.2.9.1.1.1.29 Information Schema INNODB_SYS_TABLESPACES Table 226
                  30. 1.1.1.2.9.1.1.1.30 Information Schema INNODB_SYS_TABLESTATS Table 227
                  31. 1.1.1.2.9.1.1.1.31 Information Schema INNODB_SYS_VIRTUAL Table 228
                  32. 1.1.1.2.9.1.1.1.32 Information Schema INNODB_TABLESPACES_ENCRYPTION Table 228
                  33. 1.1.1.2.9.1.1.1.33 Information Schema INNODB_TABLESPACES_SCRUBBING Table 229
                  34. 1.1.1.2.9.1.1.1.34 Information Schema INNODB_TRX Table 229
                  35. 1.1.1.2.9.1.1.1.35 Information Schema TEMP_TABLES_INFO Table 230
                2. 1.1.1.2.9.1.1.2 Information Schema MyRocks Tables 231
                  1. 1.1.1.2.9.1.1.2.1 Information Schema ROCKSDB_CFSTATS Table 232
                  2. 1.1.1.2.9.1.1.2.2 Information Schema ROCKSDB_CF_OPTIONS Table 232
                  3. 1.1.1.2.9.1.1.2.3 Information Schema ROCKSDB_COMPACTION_STATS Table 232
                  4. 1.1.1.2.9.1.1.2.4 Information Schema ROCKSDB_DBSTATS Table 232
                  5. 1.1.1.2.9.1.1.2.5 Information Schema ROCKSDB_DDL Table 232
                  6. 1.1.1.2.9.1.1.2.6 Information Schema ROCKSDB_DEADLOCK Table 233
                  7. 1.1.1.2.9.1.1.2.7 Information Schema ROCKSDB_GLOBAL_INFO Table 233
                  8. 1.1.1.2.9.1.1.2.8 Information Schema ROCKSDB_INDEX_FILE_MAP Table 233
                  9. 1.1.1.2.9.1.1.2.9 Information Schema ROCKSDB_LOCKS Table 234
                  10. 1.1.1.2.9.1.1.2.10 Information Schema ROCKSDB_PERF_CONTEXT Table 234
                  11. 1.1.1.2.9.1.1.2.11 Information Schema ROCKSDB_PERF_CONTEXT_GLOBAL Table 234
                  12. 1.1.1.2.9.1.1.2.12 Information Schema ROCKSDB_SST_PROPS Table 234
                  13. 1.1.1.2.9.1.1.2.13 Information Schema ROCKSDB_TRX Table 235
                3. 1.1.1.2.9.1.1.3 ColumnStore Information Schema Tables 235
                4. 1.1.1.2.9.1.1.4 Information Schema ALL_PLUGINS Table 237
                5. 1.1.1.2.9.1.1.5 Information Schema APPLICABLE_ROLES Table 238
                6. 1.1.1.2.9.1.1.6 Information Schema CHARACTER_SETS Table 239
                7. 1.1.1.2.9.1.1.7 Information Schema CHECK_CONSTRAINTS Table 239
                8. 1.1.1.2.9.1.1.8 Information Schema CLIENT_STATISTICS Table 241
                9. 1.1.1.2.9.1.1.9 Information Schema COLLATION_CHARACTER_SET_APPLICABILITY Table 242
                10. 1.1.1.2.9.1.1.10 Information Schema COLLATIONS Table 243
                11. 1.1.1.2.9.1.1.11 Information Schema COLUMN_PRIVILEGES Table 244
                12. 1.1.1.2.9.1.1.12 Information Schema COLUMNS Table 244
                13. 1.1.1.2.9.1.1.13 Information Schema DISKS Table 246
                14. 1.1.1.2.9.1.1.14 Information Schema ENABLED_ROLES Table 247
                15. 1.1.1.2.9.1.1.15 Information Schema ENGINES Table 247
                16. 1.1.1.2.9.1.1.16 Information Schema EVENTS Table 248
                17. 1.1.1.2.9.1.1.17 Information Schema FEEDBACK Table 249
                18. 1.1.1.2.9.1.1.18 Information Schema FILES Table 250
                19. 1.1.1.2.9.1.1.19 Information Schema GEOMETRY_COLUMNS Table 250
                20. 1.1.1.2.9.1.1.20 Information Schema GLOBAL_STATUS and SESSION_STATUS Tables 251
                21. 1.1.1.2.9.1.1.21 Information Schema GLOBAL_VARIABLES and SESSION_VARIABLES Tables 251
                22. 1.1.1.2.9.1.1.22 Information Schema INDEX_STATISTICS Table 252
                23. 1.1.1.2.9.1.1.23 Information Schema KEY_CACHES Table 252
                24. 1.1.1.2.9.1.1.24 Information Schema KEY_COLUMN_USAGE Table 253
                25. 1.1.1.2.9.1.1.25 Information Schema KEYWORDS Table 253
                26. 1.1.1.2.9.1.1.26 Information Schema LOCALES Table 261
                27. 1.1.1.2.9.1.1.27 Information Schema METADATA_LOCK_INFO Table 262
                28. 1.1.1.2.9.1.1.28 Information Schema MROONGA_STATS Table 263
                29. 1.1.1.2.9.1.1.29 Information Schema OPTIMIZER_TRACE Table 264
                30. 1.1.1.2.9.1.1.30 Information Schema PARAMETERS Table 264
                31. 1.1.1.2.9.1.1.31 Information Schema PARTITIONS Table 265
                32. 1.1.1.2.9.1.1.32 Information Schema PLUGINS Table 265
                33. 1.1.1.2.9.1.1.33 Information Schema PROCESSLIST Table 268
                34. 1.1.1.2.9.1.1.34 Information Schema PROFILING Table 269
                35. 1.1.1.2.9.1.1.35 Information Schema QUERY_CACHE_INFO Table 270
                36. 1.1.1.2.9.1.1.36 Information Schema QUERY_RESPONSE_TIME Table 270
                37. 1.1.1.2.9.1.1.37 Information Schema REFERENTIAL_CONSTRAINTS Table 271
                38. 1.1.1.2.9.1.1.38 Information Schema ROUTINES Table 271
                39. 1.1.1.2.9.1.1.39 Information Schema SCHEMA_PRIVILEGES Table 272
                40. 1.1.1.2.9.1.1.40 Information Schema SCHEMATA Table 272
                41. 1.1.1.2.9.1.1.41 Information Schema SPATIAL_REF_SYS Table 273
                42. 1.1.1.2.9.1.1.42 Information Schema SPIDER_ALLOC_MEM Table 273
                43. 1.1.1.2.9.1.1.43 Information Schema SPIDER_WRAPPER_PROTOCOLS Table 274
                44. 1.1.1.2.9.1.1.44 Information Schema SQL_FUNCTIONS Table 274
                45. 1.1.1.2.9.1.1.45 Information Schema STATISTICS Table 277
                46. 1.1.1.2.9.1.1.46 Information Schema SYSTEM_VARIABLES Table 278
                47. 1.1.1.2.9.1.1.47 Information Schema TABLE_CONSTRAINTS Table 278
                48. 1.1.1.2.9.1.1.48 Information Schema TABLE_PRIVILEGES Table 279
                49. 1.1.1.2.9.1.1.49 Information Schema TABLE_STATISTICS Table 279
                50. 1.1.1.2.9.1.1.50 Information Schema TABLES Table 279
                51. 1.1.1.2.9.1.1.51 Information Schema TABLESPACES Table 282
                52. 1.1.1.2.9.1.1.52 Information Schema THREAD_POOL_GROUPS Table 282
                53. 1.1.1.2.9.1.1.53 Information Schema THREAD_POOL_STATS Table 282
                54. 1.1.1.2.9.1.1.54 Information Schema THREAD_POOL_WAITS Table 283
                55. 1.1.1.2.9.1.1.55 Information Schema TRIGGERS Table 283
                56. 1.1.1.2.9.1.1.56 Information Schema USER_PRIVILEGES Table 284
                57. 1.1.1.2.9.1.1.57 Information Schema USER_STATISTICS Table 284
                58. 1.1.1.2.9.1.1.58 Information Schema USER_VARIABLES Table 285
                59. 1.1.1.2.9.1.1.59 Information Schema VIEWS Table 285
                60. 1.1.1.2.9.1.1.60 Information Schema WSREP_MEMBERSHIP Table 286
                61. 1.1.1.2.9.1.1.61 Information Schema WSREP_STATUS Table 286
              2. 1.1.1.2.9.1.2 Extended SHOW 286
              3. 1.1.1.2.9.1.3 TIME_MS column in INFORMATION_SCHEMA.PROCESSLIST 287
            2. 1.1.1.2.9.2 Performance Schema 287
              1. 1.1.1.2.9.2.1 Performance Schema Tables 287
                1. 1.1.1.2.9.2.1.1 List of Performance Schema Tables 290
                2. 1.1.1.2.9.2.1.2 Performance Schema accounts Table 292
                3. 1.1.1.2.9.2.1.3 Performance Schema cond_instances Table 292
                4. 1.1.1.2.9.2.1.4 Performance Schema events_stages_current Table 292
                5. 1.1.1.2.9.2.1.5 Performance Schema events_stages_history Table 293
                6. 1.1.1.2.9.2.1.6 Performance Schema events_stages_history_long Table 293
                7. 1.1.1.2.9.2.1.7 Performance Schema events_stages_summary_by_account_by_event_name Table 293
                8. 1.1.1.2.9.2.1.8 Performance Schema events_stages_summary_by_host_by_event_name Table 294
                9. 1.1.1.2.9.2.1.9 Performance Schema events_stages_summary_by_thread_by_event_name Table 295
                10. 1.1.1.2.9.2.1.10 Performance Schema events_stages_summary_by_user_by_event_name Table 295
                11. 1.1.1.2.9.2.1.11 Performance Schema events_stages_summary_global_by_event_name Table 296
                12. 1.1.1.2.9.2.1.12 Performance Schema events_statements_history Table 297
                13. 1.1.1.2.9.2.1.13 Performance Schema events_statements_history_long Table 298
                14. 1.1.1.2.9.2.1.14 Performance Schema events_statements_summary_by_account_by_event_name Table 299
                15. 1.1.1.2.9.2.1.15 Performance Schema events_statements_summary_by_digest Table 300
                16. 1.1.1.2.9.2.1.16 Performance Schema events_statements_summary_by_host_by_event_name Table 301
                17. 1.1.1.2.9.2.1.17 Performance Schema events_statements_summary_by_program Table 302
                18. 1.1.1.2.9.2.1.18 Performance Schema events_statements_summary_by_thread_by_event_name Table 303
                19. 1.1.1.2.9.2.1.19 Performance Schema events_statements_summary_by_user_by_event_name Table 305
                20. 1.1.1.2.9.2.1.20 Performance Schema events_statements_summary_global_by_event_name Table 306
                21. 1.1.1.2.9.2.1.21 Performance Schema events_transactions_current Table 308
                22. 1.1.1.2.9.2.1.22 Performance Schema events_transactions_history Table 309
                23. 1.1.1.2.9.2.1.23 Performance Schema events_transactions_history_long Table 310
                24. 1.1.1.2.9.2.1.24 Performance Schema events_transactions_summary_by_account_by_event_name Table 311
                25. 1.1.1.2.9.2.1.25 Performance Schema events_transactions_summary_by_host_by_event_name Table 311
                26. 1.1.1.2.9.2.1.26 Performance Schema events_transactions_summary_by_thread_by_event_name Table 312
                27. 1.1.1.2.9.2.1.27 Performance Schema events_transactions_summary_by_user_by_event_name Table 312
                28. 1.1.1.2.9.2.1.28 Performance Schema events_transactions_summary_global_by_event_name Table 313
                29. 1.1.1.2.9.2.1.29 Performance Schema events_waits_current Table 313
                30. 1.1.1.2.9.2.1.30 Performance Schema events_waits_history Table 314
                31. 1.1.1.2.9.2.1.31 Performance Schema events_waits_summary_by_account_by_event_name Table 314
                32. 1.1.1.2.9.2.1.32 Performance Schema events_waits_summary_by_host_by_event_name Table 315
                33. 1.1.1.2.9.2.1.33 Performance Schema events_waits_summary_by_instance Table 316
                34. 1.1.1.2.9.2.1.34 Performance Schema events_waits_summary_by_thread_by_event_name Table 316
                35. 1.1.1.2.9.2.1.35 Performance Schema events_waits_summary_by_user_by_event_name Table 317
                36. 1.1.1.2.9.2.1.36 Performance Schema events_waits_summary_global_by_event_name Table 318
                37. 1.1.1.2.9.2.1.37 Performance Schema file_instances Table 318
                38. 1.1.1.2.9.2.1.38 Performance Schema file_summary_by_event_name Table 319
                39. 1.1.1.2.9.2.1.39 Performance Schema file_summary_by_instance Table 320
                40. 1.1.1.2.9.2.1.40 Performance Schema global_status Table 321
                41. 1.1.1.2.9.2.1.41 Performance Schema hosts Table 322
                42. 1.1.1.2.9.2.1.42 Performance Schema memory_summary_by_account_by_event_name Table 322
                43. 1.1.1.2.9.2.1.43 Performance Schema memory_summary_by_host_by_event_name Table 323
                44. 1.1.1.2.9.2.1.44 Performance Schema memory_summary_by_thread_by_event_name Table 323
                45. 1.1.1.2.9.2.1.45 Performance Schema memory_summary_by_user_by_event_name Table 324
                46. 1.1.1.2.9.2.1.46 Performance Schema memory_summary_global_by_event_name Table 324
                47. 1.1.1.2.9.2.1.47 Performance Schema metadata_locks Table 325
                48. 1.1.1.2.9.2.1.48 Performance Schema mutex_instances Table 326
                49. 1.1.1.2.9.2.1.49 Performance Schema objects_summary_global_by_type Table 326
                50. 1.1.1.2.9.2.1.50 Performance Schema performance_timers Table 326
                51. 1.1.1.2.9.2.1.51 Performance Schema prepared_statements_instances Table 327
                52. 1.1.1.2.9.2.1.52 Performance Schema replication_applier_configuration Table 328
                53. 1.1.1.2.9.2.1.53 Performance Schema replication_applier_status Table 328
                54. 1.1.1.2.9.2.1.54 Performance Schema replication_applier_status_by_coordinator Table 328
                55. 1.1.1.2.9.2.1.55 Performance Schema replication_applier_status_by_worker Table 328
                56. 1.1.1.2.9.2.1.56 Performance Schema replication_connection_configuration Table 329
                57. 1.1.1.2.9.2.1.57 Performance Schema rwlock_instances Table 329
                58. 1.1.1.2.9.2.1.58 Performance Schema session_account_connect_attrs Table 330
                59. 1.1.1.2.9.2.1.59 Performance Schema session_connect_attrs Table 330
                60. 1.1.1.2.9.2.1.60 Performance Schema session_status Table 331
                61. 1.1.1.2.9.2.1.61 Performance Schema setup_actors Table 331
                62. 1.1.1.2.9.2.1.62 Performance Schema setup_consumers Table 331
                63. 1.1.1.2.9.2.1.63 Performance Schema setup_instruments Table 332
                64. 1.1.1.2.9.2.1.64 Performance Schema setup_objects Table 343
                65. 1.1.1.2.9.2.1.65 Performance Schema setup_timers Table 343
                66. 1.1.1.2.9.2.1.66 Performance Schema socket_instances Table 343
                67. 1.1.1.2.9.2.1.67 Performance Schema socket_summary_by_event_name Table 344
                68. 1.1.1.2.9.2.1.68 Performance Schema socket_summary_by_instance Table 345
                69. 1.1.1.2.9.2.1.69 Performance Schema status_by_thread Table 346
                70. 1.1.1.2.9.2.1.70 Performance Schema table_io_waits_summary_by_index_usage Table 346
                71. 1.1.1.2.9.2.1.71 Performance Schema table_io_waits_summary_by_table Table 347
                72. 1.1.1.2.9.2.1.72 Performance Schema table_lock_waits_summary_by_table Table 348
                73. 1.1.1.2.9.2.1.73 Performance Schema threads Table 349
                74. 1.1.1.2.9.2.1.74 Performance Schema users Table 350
              2. 1.1.1.2.9.2.2 Performance Schema Overview 351
              3. 1.1.1.2.9.2.3 Performance Schema Status Variables 352
              4. 1.1.1.2.9.2.4 Performance Schema System Variables 356
              5. 1.1.1.2.9.2.5 Performance Schema Digests 362
              6. 1.1.1.2.9.2.6 PERFORMANCE_SCHEMA Storage Engine 363
            3. 1.1.1.2.9.3 The mysql Database Tables 363
              1. 1.1.1.2.9.3.1 mysql.column_stats Table 364
              2. 1.1.1.2.9.3.2 mysql.columns_priv Table 365
              3. 1.1.1.2.9.3.3 mysql.db Table 365
              4. 1.1.1.2.9.3.4 mysql.event Table 366
              5. 1.1.1.2.9.3.5 mysql.func Table 367
              6. 1.1.1.2.9.3.6 mysql.general_log Table 368
              7. 1.1.1.2.9.3.7 mysql.global_priv Table 368
              8. 1.1.1.2.9.3.8 mysql.gtid_slave_pos Table 369
              9. 1.1.1.2.9.3.9 mysql.help_category Table 370
              10. 1.1.1.2.9.3.10 mysql.help_keyword Table 371
              11. 1.1.1.2.9.3.11 mysql.help_relation Table 372
              12. 1.1.1.2.9.3.12 mysql.help_topic Table 372
              13. 1.1.1.2.9.3.13 mysql.index_stats Table 373
              14. 1.1.1.2.9.3.14 mysql.innodb_index_stats 374
              15. 1.1.1.2.9.3.15 mysql.innodb_table_stats 375
              16. 1.1.1.2.9.3.16 mysql.password_reuse_check_history Table 376
              17. 1.1.1.2.9.3.17 mysql.plugin Table 376
              18. 1.1.1.2.9.3.18 mysql.proc Table 377
              19. 1.1.1.2.9.3.19 mysql.procs_priv Table 378
              20. 1.1.1.2.9.3.20 mysql.roles_mapping Table 379
              21. 1.1.1.2.9.3.21 mysql.servers Table 379
              22. 1.1.1.2.9.3.22 mysql.slow_log Table 379
              23. 1.1.1.2.9.3.23 mysql.tables_priv Table 380
              24. 1.1.1.2.9.3.24 mysql.table_stats Table 381
              25. 1.1.1.2.9.3.25 mysql.time_zone Table 381
              26. 1.1.1.2.9.3.26 mysql.time_zone_leap_second Table 382
              27. 1.1.1.2.9.3.27 mysql.time_zone_name Table 382
              28. 1.1.1.2.9.3.28 mysql.time_zone_transition Table 383
              29. 1.1.1.2.9.3.29 mysql.time_zone_transition_type Table 383
              30. 1.1.1.2.9.3.30 mysql.transaction_registry Table 384
              31. 1.1.1.2.9.3.31 mysql.user Table 384
              32. 1.1.1.2.9.3.32 Spider mysql Database Tables 386
                1. 1.1.1.2.9.3.32.1 mysql.spider_link_failed_log Table 386
                2. 1.1.1.2.9.3.32.2 mysql.spider_link_mon_servers Table 387
                3. 1.1.1.2.9.3.32.3 mysql.spider_tables Table 387
                4. 1.1.1.2.9.3.32.4 mysql.spider_table_crd Table 388
                5. 1.1.1.2.9.3.32.5 mysql.spider_table_position_for_recovery Table 388
                6. 1.1.1.2.9.3.32.6 mysql.spider_table_sts Table 389
                7. 1.1.1.2.9.3.32.7 mysql.spider_xa Table 389
                8. 1.1.1.2.9.3.32.8 mysql.spider_xa_failed_log Table 389
                9. 1.1.1.2.9.3.32.9 mysql.spider_xa_member Table 390
            4. 1.1.1.2.9.4 Sys Schema 391
              1. 1.1.1.2.9.4.1 Sys Schema sys_config Table 391
              2. 1.1.1.2.9.4.2 Sys Schema Stored Functions 392
                1. 1.1.1.2.9.4.2.1 extract_schema_from_file_name 392
                2. 1.1.1.2.9.4.2.2 extract_table_from_file_name 393
                3. 1.1.1.2.9.4.2.3 format_bytes 393
                4. 1.1.1.2.9.4.2.4 format_path 394
                5. 1.1.1.2.9.4.2.5 format_statement 394
                6. 1.1.1.2.9.4.2.6 list_add 395
                7. 1.1.1.2.9.4.2.7 list_drop 396
                8. 1.1.1.2.9.4.2.8 ps_is_account_enabled 396
                9. 1.1.1.2.9.4.2.9 ps_is_consumer_enabled 396
                10. 1.1.1.2.9.4.2.10 ps_is_instrument_default_enabled 397
                11. 1.1.1.2.9.4.2.11 ps_is_instrument_default_timed 398
                12. 1.1.1.2.9.4.2.12 ps_is_thread_instrumented 398
                13. 1.1.1.2.9.4.2.13 ps_thread_account 399
                14. 1.1.1.2.9.4.2.14 ps_thread_id 399
                15. 1.1.1.2.9.4.2.15 ps_thread_stack 400
                16. 1.1.1.2.9.4.2.16 quote_identifier 400
                17. 1.1.1.2.9.4.2.17 version_major 401
                18. 1.1.1.2.9.4.2.18 version_minor 401
                19. 1.1.1.2.9.4.2.19 version_patch 402
            5. 1.1.1.2.9.5 mariadb_schema 402
            6. 1.1.1.2.9.6 Writing Logs Into Tables 404
          10. 1.1.1.2.10 BINLOG 404
          11. 1.1.1.2.11 PURGE BINARY LOGS 404
          12. 1.1.1.2.12 CACHE INDEX 405
          13. 1.1.1.2.13 DESCRIBE 406
          14. 1.1.1.2.14 EXECUTE Statement 406
          15. 1.1.1.2.15 HELP Command 407
          16. 1.1.1.2.16 KILL [CONNECTION | QUERY] 408
          17. 1.1.1.2.17 LOAD INDEX 409
          18. 1.1.1.2.18 RESET 409
          19. 1.1.1.2.19 SHUTDOWN 409
          20. 1.1.1.2.20 USE 411
        3. 1.1.1.3 Data Definition 411
          1. 1.1.1.3.1 CREATE 411
            1. 1.1.1.3.1.1 CREATE DATABASE 412
            2. 1.1.1.3.1.2 CREATE EVENT 414
            3. 1.1.1.3.1.3 CREATE FUNCTION 417
            4. 1.1.1.3.1.4 CREATE FUNCTION UDF 420
            5. 1.1.1.3.1.5 CREATE INDEX 422
            6. 1.1.1.3.1.6 CREATE LOGFILE GROUP 424
            7. 1.1.1.3.1.7 CREATE PACKAGE 425
            8. 1.1.1.3.1.8 CREATE PACKAGE BODY 427
            9. 1.1.1.3.1.9 CREATE PROCEDURE 430
            10. 1.1.1.3.1.10 CREATE ROLE 432
            11. 1.1.1.3.1.11 CREATE SEQUENCE 432
            12. 1.1.1.3.1.12 CREATE SERVER 432
            13. 1.1.1.3.1.13 CREATE TABLE 434
            14. 1.1.1.3.1.14 CREATE TABLESPACE 434
            15. 1.1.1.3.1.15 CREATE TRIGGER 434
            16. 1.1.1.3.1.16 CREATE USER 436
            17. 1.1.1.3.1.17 CREATE VIEW 436
            18. 1.1.1.3.1.18 Silent Column Changes 439
            19. 1.1.1.3.1.19 Generated (Virtual and Persistent/Stored) Columns 440
            20. 1.1.1.3.1.20 Invisible Columns 445
          2. 1.1.1.3.2 ALTER 446
            1. 1.1.1.3.2.1 ALTER TABLE 446
            2. 1.1.1.3.2.2 ALTER DATABASE 446
            3. 1.1.1.3.2.3 ALTER EVENT 446
            4. 1.1.1.3.2.4 ALTER FUNCTION 446
            5. 1.1.1.3.2.5 ALTER LOGFILE GROUP 446
            6. 1.1.1.3.2.6 ALTER PROCEDURE 447
            7. 1.1.1.3.2.7 ALTER SEQUENCE 447
            8. 1.1.1.3.2.8 ALTER SERVER 447
            9. 1.1.1.3.2.9 ALTER TABLESPACE 447
            10. 1.1.1.3.2.10 ALTER USER 447
            11. 1.1.1.3.2.11 ALTER VIEW 447
          3. 1.1.1.3.3 DROP 447
            1. 1.1.1.3.3.1 DROP DATABASE 447
            2. 1.1.1.3.3.2 DROP EVENT 448
            3. 1.1.1.3.3.3 DROP FUNCTION 449
            4. 1.1.1.3.3.4 DROP FUNCTION UDF 450
            5. 1.1.1.3.3.5 DROP INDEX 450
            6. 1.1.1.3.3.6 DROP LOGFILE GROUP 451
            7. 1.1.1.3.3.7 DROP PACKAGE 451
            8. 1.1.1.3.3.8 DROP PACKAGE BODY 452
            9. 1.1.1.3.3.9 DROP PROCEDURE 452
            10. 1.1.1.3.3.10 DROP ROLE 453
            11. 1.1.1.3.3.11 DROP SEQUENCE 453
            12. 1.1.1.3.3.12 DROP SERVER 453
            13. 1.1.1.3.3.13 DROP TABLE 454
            14. 1.1.1.3.3.14 DROP TABLESPACE 454
            15. 1.1.1.3.3.15 DROP TRIGGER 454
            16. 1.1.1.3.3.16 DROP USER 455
            17. 1.1.1.3.3.17 DROP VIEW 455
          4. 1.1.1.3.4 Atomic DDL 456
          5. 1.1.1.3.5 CONSTRAINT 458
          6. 1.1.1.3.6 MERGE 460
          7. 1.1.1.3.7 RENAME TABLE 460
          8. 1.1.1.3.8 TRUNCATE TABLE 460
        4. 1.1.1.4 Data Manipulation 460
          1. 1.1.1.4.1 Selecting Data 460
            1. 1.1.1.4.1.1 SELECT 462
            2. 1.1.1.4.1.2 Joins & Subqueries 464
              1. 1.1.1.4.1.2.1 Joins 464
                1. 1.1.1.4.1.2.1.1 Joining Tables with JOIN Clauses 465
                2. 1.1.1.4.1.2.1.2 More Advanced Joins 465
                3. 1.1.1.4.1.2.1.3 JOIN Syntax 467
                4. 1.1.1.4.1.2.1.4 Comma vs JOIN 468
              2. 1.1.1.4.1.2.2 Subqueries 468
                1. 1.1.1.4.1.2.2.1 Scalar Subqueries 469
                2. 1.1.1.4.1.2.2.2 Row Subqueries 469
                3. 1.1.1.4.1.2.2.3 Subqueries and ALL 470
                4. 1.1.1.4.1.2.2.4 Subqueries and ANY 471
                5. 1.1.1.4.1.2.2.5 Subqueries and EXISTS 472
                6. 1.1.1.4.1.2.2.6 Subqueries in a FROM Clause 473
                7. 1.1.1.4.1.2.2.7 Subquery Optimizations 473
                  1. 1.1.1.4.1.2.2.7.1 Subquery Optimizations Map 473
                  2. 1.1.1.4.1.2.2.7.2 Semi-join Subquery Optimizations 473
                  3. 1.1.1.4.1.2.2.7.3 Table Pullout Optimization 473
                  4. 1.1.1.4.1.2.2.7.4 Non-semi-join Subquery Optimizations 473
                  5. 1.1.1.4.1.2.2.7.5 Subquery Cache 473
                  6. 1.1.1.4.1.2.2.7.6 Condition Pushdown Into IN subqueries 473
                  7. 1.1.1.4.1.2.2.7.7 Conversion of Big IN Predicates Into Subqueries 473
                  8. 1.1.1.4.1.2.2.7.8 EXISTS-to-IN Optimization 474
                  9. 1.1.1.4.1.2.2.7.9 Optimizing GROUP BY and DISTINCE Clauses in Subqueries 474
                8. 1.1.1.4.1.2.2.8 Subqueries and JOINs 474
                9. 1.1.1.4.1.2.2.9 Subquery Limitations 475
              3. 1.1.1.4.1.2.3 UNION 476
              4. 1.1.1.4.1.2.4 EXCEPT 479
              5. 1.1.1.4.1.2.5 INTERSECT 481
              6. 1.1.1.4.1.2.6 Precedence Control in Table Operations 484
              7. 1.1.1.4.1.2.7 MINUS 484
            3. 1.1.1.4.1.3 LIMIT 484
            4. 1.1.1.4.1.4 ORDER BY 487
            5. 1.1.1.4.1.5 GROUP BY 488
            6. 1.1.1.4.1.6 Common Table Expressions 490
              1. 1.1.1.4.1.6.1 WITH 490
              2. 1.1.1.4.1.6.2 Non-Recursive Common Table Expressions Overview 492
              3. 1.1.1.4.1.6.3 Recursive Common Table Expressions Overview 493
            7. 1.1.1.4.1.7 SELECT WITH ROLLUP 498
            8. 1.1.1.4.1.8 SELECT INTO OUTFILE 500
            9. 1.1.1.4.1.9 SELECT INTO DUMPFILE 500
            10. 1.1.1.4.1.10 FOR UPDATE 501
            11. 1.1.1.4.1.11 LOCK IN SHARE MODE 501
            12. 1.1.1.4.1.12 Optimizer Hints 502
            13. 1.1.1.4.1.13 PROCEDURE 502
            14. 1.1.1.4.1.14 HANDLER 502
            15. 1.1.1.4.1.15 DUAL 502
            16. 1.1.1.4.1.16 SELECT ... OFFSET ... FETCH 503
          2. 1.1.1.4.2 Inserting & Loading Data 504
            1. 1.1.1.4.2.1 INSERT 504
            2. 1.1.1.4.2.2 INSERT DELAYED 507
            3. 1.1.1.4.2.3 INSERT SELECT 508
            4. 1.1.1.4.2.4 LOAD Data into Tables or Index 508
              1. 1.1.1.4.2.4.1 LOAD DATA INFILE 509
              2. 1.1.1.4.2.4.2 LOAD INDEX 511
              3. 1.1.1.4.2.4.3 LOAD XML 511
              4. 1.1.1.4.2.4.4 LOAD_FILE 512
            5. 1.1.1.4.2.5 Concurrent Inserts 513
            6. 1.1.1.4.2.6 HIGH_PRIORITY and LOW_PRIORITY 513
            7. 1.1.1.4.2.7 IGNORE 513
            8. 1.1.1.4.2.8 INSERT - Default & Duplicate Values 513
            9. 1.1.1.4.2.9 INSERT IGNORE 514
            10. 1.1.1.4.2.10 INSERT ON DUPLICATE KEY UPDATE 515
            11. 1.1.1.4.2.11 INSERT...RETURNING 517
          3. 1.1.1.4.3 Changing & Deleting Data 519
            1. 1.1.1.4.3.1 DELETE 519
            2. 1.1.1.4.3.2 HIGH_PRIORITY and LOW_PRIORITY 519
            3. 1.1.1.4.3.3 IGNORE 519
            4. 1.1.1.4.3.4 REPLACE 519
            5. 1.1.1.4.3.5 REPLACE...RETURNING 519
            6. 1.1.1.4.3.6 TRUNCATE TABLE 521
            7. 1.1.1.4.3.7 UPDATE 521
        5. 1.1.1.5 Prepared Statements 521
          1. 1.1.1.5.1 PREPARE Statement 521
          2. 1.1.1.5.2 Out Parameters in PREPARE 524
          3. 1.1.1.5.3 EXECUTE STATEMENT 524
          4. 1.1.1.5.4 DEALLOCATE / DROP PREPARE 524
          5. 1.1.1.5.5 EXECUTE IMMEDIATE 525
        6. 1.1.1.6 Programmatic & Compound Statements 527
          1. 1.1.1.6.1 Using Compound Statements Outside of Stored Programs 528
          2. 1.1.1.6.2 BEGIN END 528
          3. 1.1.1.6.3 CASE Statement 529
          4. 1.1.1.6.4 DECLARE CONDITION 530
          5. 1.1.1.6.5 DECLARE HANDLER 530
          6. 1.1.1.6.6 DECLARE Variable 532
          7. 1.1.1.6.7 FOR 533
          8. 1.1.1.6.8 GOTO 535
          9. 1.1.1.6.9 IF 536
          10. 1.1.1.6.10 ITERATE 536
          11. 1.1.1.6.11 Labels 537
          12. 1.1.1.6.12 LEAVE 537
          13. 1.1.1.6.13 LOOP 538
          14. 1.1.1.6.14 REPEAT LOOP 538
          15. 1.1.1.6.15 RESIGNAL 540
          16. 1.1.1.6.16 RETURN 541
          17. 1.1.1.6.17 SELECT INTO 542
          18. 1.1.1.6.18 SET Variable 542
          19. 1.1.1.6.19 SIGNAL 543
          20. 1.1.1.6.20 WHILE 544
        7. 1.1.1.7 Stored Routine Statements 545
          1. 1.1.1.7.1 CALL 545
          2. 1.1.1.7.2 DO 545
        8. 1.1.1.8 Table Statements 546
        9. 1.1.1.9 Transactions 546
          1. 1.1.1.9.1 START TRANSACTION 546
          2. 1.1.1.9.2 COMMIT 547
          3. 1.1.1.9.3 ROLLBACK 548
          4. 1.1.1.9.4 SET TRANSACTION 548
          5. 1.1.1.9.5 LOCK TABLES 548
          6. 1.1.1.9.6 SAVEPOINT 550
          7. 1.1.1.9.7 Metadata Locking 550
          8. 1.1.1.9.8 SQL statements That Cause an Implicit Commit 551
          9. 1.1.1.9.9 Transaction Timeouts 552
          10. 1.1.1.9.10 UNLOCK TABLES 552
          11. 1.1.1.9.11 WAIT and NOWAIT 554
          12. 1.1.1.9.12 XA Transactions 554
        10. 1.1.1.10 HELP Command 556
        11. 1.1.1.11 Comment Syntax 556
        12. 1.1.1.12 Built-in Functions 558
      2. 1.1.2 SQL Language Structure 558
        1. 1.1.2.1 Identifier Names 558
        2. 1.1.2.2 Identifier Case-sensitivity 560
        3. 1.1.2.3 Binary Literals 561
        4. 1.1.2.4 Boolean Literals 561
        5. 1.1.2.5 Date and Time Literals 561
        6. 1.1.2.6 Hexadecimal Literals 563
        7. 1.1.2.7 Identifier Qualifiers 564
        8. 1.1.2.8 Identifier to File Name Mapping 565
        9. 1.1.2.9 MariaDB Error Codes 566
        10. 1.1.2.10 Numeric Literals 596
        11. 1.1.2.11 Reserved Words 596
        12. 1.1.2.12 SQLSTATE 602
        13. 1.1.2.13 String Literals 602
        14. 1.1.2.14 Table Value Constructors 604
        15. 1.1.2.15 User-Defined Variables 605
      3. 1.1.3 Geographic & Geometric Features 605
        1. 1.1.3.1 GIS Resources 606
        2. 1.1.3.2 GIS features in 5.3.3 606
        3. 1.1.3.3 Geometry Types 607
        4. 1.1.3.4 Geometry Hierarchy 608
        5. 1.1.3.5 Geometry Constructors 609
        6. 1.1.3.6 Geometry Properties 609
        7. 1.1.3.7 Geometry Relations 609
        8. 1.1.3.8 LineString Properties 609
        9. 1.1.3.9 MBR (Minimum Bounding Rectangle) 609
        10. 1.1.3.10 Point Properties 609
        11. 1.1.3.11 Polygon Properties 609
        12. 1.1.3.12 WKB 609
        13. 1.1.3.13 WKT 609
        14. 1.1.3.14 MySQL/MariaDB Spatial Support Matrix 609
        15. 1.1.3.15 SPATIAL INDEX 612
        16. 1.1.3.16 GeoJSON 613
          1. 1.1.3.16.1 ST_AsGeoJSON 613
          2. 1.1.3.16.2 ST_GeomFromGeoJSON 614
      4. 1.1.4 NoSQL 614
        1. 1.1.4.1 CONNECT 614
        2. 1.1.4.2 HANDLER 615
          1. 1.1.4.2.1 HANDLER Commands 616
          2. 1.1.4.2.2 HANDLER for MEMORY Tables 617
        3. 1.1.4.3 HandlerSocket 618
          1. 1.1.4.3.1 HandlerSocket Installation 618
          2. 1.1.4.3.2 HandlerSocket Configuration Options 618
          3. 1.1.4.3.3 HandlerSocket Client Libraries 621
          4. 1.1.4.3.4 Testing HandlerSocket in a Source Distribution 621
          5. 1.1.4.3.5 HandlerSocket External Resources 622
        4. 1.1.4.4 Dynamic Columns 622
        5. 1.1.4.5 Dynamic Columns from MariaDB 10 626
        6. 1.1.4.6 Dynamic Column API 628
        7. 1.1.4.7 JSON Functions 632
        8. 1.1.4.8 LOAD_FILE 632
      5. 1.1.5 Operators 632
        1. 1.1.5.1 Arithmetic Operators 634
          1. 1.1.5.1.1 Addition Operator (+) 634
          2. 1.1.5.1.2 DIV 634
          3. 1.1.5.1.3 Division Operator (/) 634
          4. 1.1.5.1.4 MOD 634
          5. 1.1.5.1.5 Modulo Operator (%) 634
          6. 1.1.5.1.6 Multiplication Operator (*) 635
          7. 1.1.5.1.7 Subtraction Operator (-) 635
        2. 1.1.5.2 Assignment Operators 635
          1. 1.1.5.2.1 Assignment Operator (:=) 635
          2. 1.1.5.2.2 Assignment Operator (=) 635
        3. 1.1.5.3 Bit Functions and Operators 636
        4. 1.1.5.4 Comparison Operators 636
          1. 1.1.5.4.1 Not Equal Operator: != 636
          2. 1.1.5.4.2 < 637
          3. 1.1.5.4.3 <= 638
          4. 1.1.5.4.4 <=> 638
          5. 1.1.5.4.5 = 639
          6. 1.1.5.4.6 > 640
          7. 1.1.5.4.7 >= 641
          8. 1.1.5.4.8 BETWEEN AND 641
          9. 1.1.5.4.9 COALESCE 643
          10. 1.1.5.4.10 GREATEST 644
          11. 1.1.5.4.11 IN 644
          12. 1.1.5.4.12 INTERVAL 645
          13. 1.1.5.4.13 IS 646
          14. 1.1.5.4.14 IS NOT 646
          15. 1.1.5.4.15 IS NOT NULL 647
          16. 1.1.5.4.16 IS NULL 647
          17. 1.1.5.4.17 ISNULL 648
          18. 1.1.5.4.18 LEAST 648
          19. 1.1.5.4.19 NOT BETWEEN 649
          20. 1.1.5.4.20 NOT IN 649
        5. 1.1.5.5 Logical Operators 650
          1. 1.1.5.5.1 ! 650
          2. 1.1.5.5.2 && 651
          3. 1.1.5.5.3 XOR 652
          4. 1.1.5.5.4 || 653
        6. 1.1.5.6 Operator Precedence 654
      6. 1.1.6 Sequences 654
        1. 1.1.6.1 Sequence Overview 655
        2. 1.1.6.2 CREATE SEQUENCE 658
        3. 1.1.6.3 SHOW CREATE SEQUENCE 660
        4. 1.1.6.4 ALTER SEQUENCE 660
        5. 1.1.6.5 DROP SEQUENCE 661
        6. 1.1.6.6 SEQUENCE Functions 662
          1. 1.1.6.6.1 LASTVAL 662
          2. 1.1.6.6.2 NEXT VALUE for sequence_name 662
          3. 1.1.6.6.3 NEXTVAL 663
          4. 1.1.6.6.4 PREVIOUS VALUE FOR sequence_name 663
          5. 1.1.6.6.5 SETVAL() 664
        7. 1.1.6.7 SHOW TABLES 666
      7. 1.1.7 Temporal Tables 666
        1. 1.1.7.1 System-Versioned Tables 666
        2. 1.1.7.2 Application-Time Periods 671
        3. 1.1.7.3 Bitemporal Tables 675
    2. 1.2 Built-in Functions 675
      1. 1.2.1 Function and Operator Reference 676
      2. 1.2.2 String Functions 685
        1. 1.2.2.1 Regular Expressions Functions 687
          1. 1.2.2.1.1 Regular Expressions Overview 688
          2. 1.2.2.1.2 Perl Compatible Regular Expressions (PCRE) Documentation 696
          3. 1.2.2.1.3 NOT REGEXP 705
          4. 1.2.2.1.4 REGEXP 706
          5. 1.2.2.1.5 REGEXP_INSTR 707
          6. 1.2.2.1.6 REGEXP_REPLACE 707
          7. 1.2.2.1.7 REGEXP_SUBSTR 708
          8. 1.2.2.1.8 RLIKE 709
        2. 1.2.2.2 Dynamic Columns Functions 709
          1. 1.2.2.2.1 COLUMN_ADD 709
          2. 1.2.2.2.2 COLUMN_CHECK 710
          3. 1.2.2.2.3 COLUMN_CREATE 710
          4. 1.2.2.2.4 COLUMN_DELETE 710
          5. 1.2.2.2.5 COLUMN_EXISTS 711
          6. 1.2.2.2.6 COLUMN_GET 711
          7. 1.2.2.2.7 COLUMN_JSON 711
          8. 1.2.2.2.8 COLUMN_LIST 712
        3. 1.2.2.3 ASCII 712
        4. 1.2.2.4 BIN 712
        5. 1.2.2.5 BINARY Operator 713
        6. 1.2.2.6 BIT_LENGTH 713
        7. 1.2.2.7 CAST 714
        8. 1.2.2.8 CHAR Function 716
        9. 1.2.2.9 CHAR_LENGTH 716
        10. 1.2.2.10 CHARACTER_LENGTH 717
        11. 1.2.2.11 CHR 717
        12. 1.2.2.12 CONCAT 718
        13. 1.2.2.13 CONCAT_WS 719
        14. 1.2.2.14 CONVERT 720
        15. 1.2.2.15 ELT 721
        16. 1.2.2.16 EXPORT_SET 721
        17. 1.2.2.17 EXTRACTVALUE 722
        18. 1.2.2.18 FIELD 723
        19. 1.2.2.19 FIND_IN_SET 724
        20. 1.2.2.20 FORMAT 725
        21. 1.2.2.21 FROM_BASE64 725
        22. 1.2.2.22 HEX 726
        23. 1.2.2.23 INSERT Function 726
        24. 1.2.2.24 LENGTH 727
        25. 1.2.2.25 LENGTHB 728
        26. 1.2.2.26 LIKE 728
        27. 1.2.2.27 LOAD_FILE 730
        28. 1.2.2.28 LOCATE 730
        29. 1.2.2.29 LOWER 731
        30. 1.2.2.30 LPAD 731
        31. 1.2.2.31 LTRIM 732
        32. 1.2.2.32 MAKE_SET 733
        33. 1.2.2.33 MATCH AGAINST 733
        34. 1.2.2.34 Full-Text Index Stopwords 734
        35. 1.2.2.35 MID 734
        36. 1.2.2.36 NOT LIKE 735
        37. 1.2.2.37 NOT REGEXP 735
        38. 1.2.2.38 OCTET_LENGTH 735
        39. 1.2.2.39 ORD 735
        40. 1.2.2.40 POSITION 736
        41. 1.2.2.41 QUOTE 736
        42. 1.2.2.42 REPEAT Function 736
        43. 1.2.2.43 REPLACE Function 737
        44. 1.2.2.44 REVERSE 737
        45. 1.2.2.45 RIGHT 737
        46. 1.2.2.46 RPAD 738
        47. 1.2.2.47 RTRIM 739
        48. 1.2.2.48 SFORMAT 739
        49. 1.2.2.49 SOUNDEX 740
        50. 1.2.2.50 SOUNDS LIKE 741
        51. 1.2.2.51 SPACE 741
        52. 1.2.2.52 STRCMP 741
        53. 1.2.2.53 SUBSTR 742
        54. 1.2.2.54 SUBSTRING 742
        55. 1.2.2.55 SUBSTRING_INDEX 743
        56. 1.2.2.56 TO_BASE64 744
        57. 1.2.2.57 TO_CHAR 745
        58. 1.2.2.58 TRIM 746
        59. 1.2.2.59 TRIM_ORACLE 746
        60. 1.2.2.60 UCASE 747
        61. 1.2.2.61 UNCOMPRESS 747
        62. 1.2.2.62 UNCOMPRESSED_LENGTH 747
        63. 1.2.2.63 UNHEX 748
        64. 1.2.2.64 UPDATEXML 748
        65. 1.2.2.65 UPPER 749
        66. 1.2.2.66 WEIGHT_STRING 749
        67. 1.2.2.67 Type Conversion 750
      3. 1.2.3 Date & Time Functions 752
        1. 1.2.3.1 Microseconds in MariaDB 755
        2. 1.2.3.2 Date and Time Units 756
        3. 1.2.3.3 ADD_MONTHS 757
        4. 1.2.3.4 ADDDATE 758
        5. 1.2.3.5 ADDTIME 759
        6. 1.2.3.6 CONVERT_TZ 759
        7. 1.2.3.7 CURDATE 760
        8. 1.2.3.8 CURRENT_DATE 761
        9. 1.2.3.9 CURRENT_TIME 761
        10. 1.2.3.10 CURRENT_TIMESTAMP 761
        11. 1.2.3.11 CURTIME 761
        12. 1.2.3.12 DATE FUNCTION 762
        13. 1.2.3.13 DATEDIFF 762
        14. 1.2.3.14 DATE_ADD 763
        15. 1.2.3.15 DATE_FORMAT 764
        16. 1.2.3.16 DATE_SUB 766
        17. 1.2.3.17 DAY 767
        18. 1.2.3.18 DAYNAME 767
        19. 1.2.3.19 DAYOFMONTH 768
        20. 1.2.3.20 DAYOFWEEK 768
        21. 1.2.3.21 DAYOFYEAR 769
        22. 1.2.3.22 EXTRACT 769
        23. 1.2.3.23 FROM_DAYS 770
        24. 1.2.3.24 FROM_UNIXTIME 770
        25. 1.2.3.25 GET_FORMAT 772
        26. 1.2.3.26 HOUR 773
        27. 1.2.3.27 LAST_DAY 774
        28. 1.2.3.28 LOCALTIME 774
        29. 1.2.3.29 LOCALTIMESTAMP 774
        30. 1.2.3.30 MAKEDATE 775
        31. 1.2.3.31 MAKETIME 775
        32. 1.2.3.32 MICROSECOND 776
        33. 1.2.3.33 MINUTE 777
        34. 1.2.3.34 MONTH 777
        35. 1.2.3.35 MONTHNAME 778
        36. 1.2.3.36 NOW 778
        37. 1.2.3.37 PERIOD_ADD 779
        38. 1.2.3.38 PERIOD_DIFF 780
        39. 1.2.3.39 QUARTER 780
        40. 1.2.3.40 SECOND 781
        41. 1.2.3.41 SEC_TO_TIME 781
        42. 1.2.3.42 STR_TO_DATE 782
        43. 1.2.3.43 SUBDATE 783
        44. 1.2.3.44 SUBTIME 784
        45. 1.2.3.45 SYSDATE 785
        46. 1.2.3.46 TIME Function 786
        47. 1.2.3.47 TIMEDIFF 786
        48. 1.2.3.48 TIMESTAMP FUNCTION 786
        49. 1.2.3.49 TIMESTAMPADD 787
        50. 1.2.3.50 TIMESTAMPDIFF 787
        51. 1.2.3.51 TIME_FORMAT 788
        52. 1.2.3.52 TIME_TO_SEC 789
        53. 1.2.3.53 TO_DAYS 789
        54. 1.2.3.54 TO_SECONDS 790
        55. 1.2.3.55 UNIX_TIMESTAMP 790
        56. 1.2.3.56 UTC_DATE 792
        57. 1.2.3.57 UTC_TIME 792
        58. 1.2.3.58 UTC_TIMESTAMP 792
        59. 1.2.3.59 WEEK 793
        60. 1.2.3.60 WEEKDAY 794
        61. 1.2.3.61 WEEKOFYEAR 795
        62. 1.2.3.62 YEAR 796
        63. 1.2.3.63 YEARWEEK 796
      4. 1.2.4 Aggregate Functions 797
        1. 1.2.4.1 Stored Aggregate Functions 798
        2. 1.2.4.2 AVG 800
        3. 1.2.4.3 BIT_AND 801
        4. 1.2.4.4 BIT_OR 802
        5. 1.2.4.5 BIT_XOR 803
        6. 1.2.4.6 COUNT 804
        7. 1.2.4.7 COUNT DISTINCT 805
        8. 1.2.4.8 GROUP_CONCAT 806
        9. 1.2.4.9 JSON_ARRAYAGG 807
        10. 1.2.4.10 JSON_OBJECTAGG 808
        11. 1.2.4.11 MAX 808
        12. 1.2.4.12 MIN 810
        13. 1.2.4.13 STD 811
        14. 1.2.4.14 STDDEV 812
        15. 1.2.4.15 STDDEV_POP 813
        16. 1.2.4.16 STDDEV_SAMP 814
        17. 1.2.4.17 SUM 814
        18. 1.2.4.18 VARIANCE 816
        19. 1.2.4.19 VAR_POP 817
        20. 1.2.4.20 VAR_SAMP 818
      5. 1.2.5 Numeric Functions 819
        1. 1.2.5.1 Addition Operator (+) 821
        2. 1.2.5.2 Subtraction Operator (-) 821
        3. 1.2.5.3 Division Operator (/) 822
        4. 1.2.5.4 Multiplication Operator (*) 823
        5. 1.2.5.5 Modulo Operator (%) 824
        6. 1.2.5.6 DIV 824
        7. 1.2.5.7 ABS 825
        8. 1.2.5.8 ACOS 825
        9. 1.2.5.9 ASIN 826
        10. 1.2.5.10 ATAN 827
        11. 1.2.5.11 ATAN2 827
        12. 1.2.5.12 CEIL 828
        13. 1.2.5.13 CEILING 828
        14. 1.2.5.14 CONV 828
        15. 1.2.5.15 COS 829
        16. 1.2.5.16 COT 829
        17. 1.2.5.17 CRC32 830
        18. 1.2.5.18 CRC32C 830
        19. 1.2.5.19 DEGREES 831
        20. 1.2.5.20 EXP 832
        21. 1.2.5.21 FLOOR 832
        22. 1.2.5.22 GREATEST 832
        23. 1.2.5.23 LEAST 833
        24. 1.2.5.24 LN 833
        25. 1.2.5.25 LOG 833
        26. 1.2.5.26 LOG10 834
        27. 1.2.5.27 LOG2 834
        28. 1.2.5.28 MOD 835
        29. 1.2.5.29 OCT 835
        30. 1.2.5.30 PI 836
        31. 1.2.5.31 POW 836
        32. 1.2.5.32 POWER 837
        33. 1.2.5.33 RADIANS 837
        34. 1.2.5.34 RAND 838
        35. 1.2.5.35 ROUND 839
        36. 1.2.5.36 SIGN 840
        37. 1.2.5.37 SIN 841
        38. 1.2.5.38 SQRT 841
        39. 1.2.5.39 TAN 842
        40. 1.2.5.40 TRUNCATE 842
      6. 1.2.6 Control Flow Functions 843
        1. 1.2.6.1 CASE OPERATOR 844
        2. 1.2.6.2 DECODE 844
        3. 1.2.6.3 DECODE_ORACLE 845
        4. 1.2.6.4 IF Function 845
        5. 1.2.6.5 IFNULL 846
        6. 1.2.6.6 NULLIF 847
        7. 1.2.6.7 NVL 848
        8. 1.2.6.8 NVL2 848
      7. 1.2.7 Pseudo Columns 848
        1. 1.2.7.1 _rowid 848
      8. 1.2.8 Secondary Functions 849
        1. 1.2.8.1 Bit Functions and Operators 849
          1. 1.2.8.1.1 Operator Precedence 849
          2. 1.2.8.1.2 & 850
          3. 1.2.8.1.3 << 850
          4. 1.2.8.1.4 >> 850
          5. 1.2.8.1.5 BIT_COUNT 851
          6. 1.2.8.1.6 ^ 851
          7. 1.2.8.1.7 | 851
          8. 1.2.8.1.8 ~ 852
          9. 1.2.8.1.9 Parentheses 852
          10. 1.2.8.1.10 TRUE FALSE 853
        2. 1.2.8.2 Encryption, Hashing and Compression Functions 853
          1. 1.2.8.2.1 AES_DECRYPT 854
          2. 1.2.8.2.2 AES_ENCRYPT 854
          3. 1.2.8.2.3 COMPRESS 854
          4. 1.2.8.2.4 DECODE 855
          5. 1.2.8.2.5 DES_DECRYPT 855
          6. 1.2.8.2.6 DES_ENCRYPT 855
          7. 1.2.8.2.7 ENCODE 856
          8. 1.2.8.2.8 ENCRYPT 856
          9. 1.2.8.2.9 MD5 857
          10. 1.2.8.2.10 OLD_PASSWORD 857
          11. 1.2.8.2.11 PASSWORD 857
          12. 1.2.8.2.12 SHA1 858
          13. 1.2.8.2.13 SHA2 859
          14. 1.2.8.2.14 UNCOMPRESS 859
          15. 1.2.8.2.15 UNCOMPRESSED_LENGTH 859
        3. 1.2.8.3 Information Functions 859
          1. 1.2.8.3.1 BENCHMARK 860
          2. 1.2.8.3.2 BINLOG_GTID_POS 861
          3. 1.2.8.3.3 CHARSET 861
          4. 1.2.8.3.4 COERCIBILITY 862
          5. 1.2.8.3.5 COLLATION 862
          6. 1.2.8.3.6 CONNECTION_ID 863
          7. 1.2.8.3.7 CURRENT_ROLE 863
          8. 1.2.8.3.8 CURRENT_USER 864
          9. 1.2.8.3.9 DATABASE 864
          10. 1.2.8.3.10 DECODE_HISTOGRAM 865
          11. 1.2.8.3.11 DEFAULT 866
          12. 1.2.8.3.12 FOUND_ROWS 867
          13. 1.2.8.3.13 LAST_INSERT_ID 868
          14. 1.2.8.3.14 LAST_VALUE 870
          15. 1.2.8.3.15 PROCEDURE ANALYSE 872

1 Using MariaDB Server

Documentation on using MariaDB Server.

1.1 SQL Statements & Structure

The letters SQL stand for Structured Query Language. As with all languages—even computer languages—there are grammar rules. This includes a certain structure to statements, acceptable punctuation (i.e., operators and delimiters), and a vocabulary (i.e., reserve words).

There are 9 related questions.

1.1.1 SQL Statements

Complete list of SQL statements for data definition, data manipulation, etc.

There are 16 related questions.

1.1.1.1 Account Management SQL Commands

CREATE/DROP USER, GRANT, REVOKE, SET PASSWORD etc.

There are 2 related questions.

1.1.1.1.1 CREATE USER

Syntax

CREATE [OR REPLACE] USER [IF NOT EXISTS] 
 user_specification [,user_specification ...] 
  [REQUIRE {NONE | tls_option [[AND] tls_option ...] }]
  [WITH resource_option [resource_option ...] ]
  [lock_option] [password_option] 

user_specification:
  username [authentication_option]

authentication_option:
  IDENTIFIED BY 'password' 
  | IDENTIFIED BY PASSWORD 'password_hash'
  | IDENTIFIED {VIA|WITH} authentication_rule [OR authentication_rule  ...]

authentication_rule:
    authentication_plugin
  | authentication_plugin {USING|AS} 'authentication_string'
  | authentication_plugin {USING|AS} PASSWORD('password')

tls_option:
  SSL 
  | X509
  | CIPHER 'cipher'
  | ISSUER 'issuer'
  | SUBJECT 'subject'

resource_option:
  MAX_QUERIES_PER_HOUR count
  | MAX_UPDATES_PER_HOUR count
  | MAX_CONNECTIONS_PER_HOUR count
  | MAX_USER_CONNECTIONS count
  | MAX_STATEMENT_TIME time

password_option:
  PASSWORD EXPIRE
  | PASSWORD EXPIRE DEFAULT
  | PASSWORD EXPIRE NEVER
  | PASSWORD EXPIRE INTERVAL N DAY

lock_option:
    ACCOUNT LOCK
  | ACCOUNT UNLOCK
}

Contents

  1. Syntax
  2. Description
  3. OR REPLACE
  4. IF NOT EXISTS
  5. Authentication Options
    1. IDENTIFIED BY 'password'
    2. IDENTIFIED BY PASSWORD 'password_hash'
    3. IDENTIFIED {VIA|WITH} authentication_plugin
  6. TLS Options
  7. Resource Limit Options
  8. Account Names
    1. Host Name Component
    2. User Name Component
    3. Anonymous Accounts
      1. Fixing a Legacy Default Anonymous Account
  9. Password Expiry
  10. Account Locking
  11. See Also

Description

The CREATE USER statement creates new MariaDB accounts. To use it, you must have the global CREATE USER privilege or the INSERT privilege for the mysql database. For each account, CREATE USER creates a new row in mysql.user (until MariaDB 10.3 this is a table, from MariaDB 10.4 it's a view) or mysql.global_priv_table (from MariaDB 10.4) that has no privileges.

If any of the specified accounts, or any permissions for the specified accounts, already exist, then the server returns ERROR 1396 (HY000). If an error occurs, CREATE USER will still create the accounts that do not result in an error. Only one error is produced for all users which have not been created:

ERROR 1396 (HY000): 
  Operation CREATE USER failed for 'u1'@'%','u2'@'%'

CREATE USER, DROP USER, CREATE ROLE, and DROP ROLE all produce the same error code when they fail.

See Account Names below for details on how account names are specified.

OR REPLACE

If the optional OR REPLACE clause is used, it is basically a shortcut for:

DROP USER IF EXISTS name;
CREATE USER name ...;

For example:

CREATE USER foo2@test IDENTIFIED BY 'password';
ERROR 1396 (HY000): Operation CREATE USER failed for 'foo2'@'test'

CREATE OR REPLACE USER foo2@test IDENTIFIED BY 'password';
Query OK, 0 rows affected (0.00 sec)

IF NOT EXISTS

When the IF NOT EXISTS clause is used, MariaDB will return a warning instead of an error if the specified user already exists.

For example:

CREATE USER foo2@test IDENTIFIED BY 'password';
ERROR 1396 (HY000): Operation CREATE USER failed for 'foo2'@'test'

CREATE USER IF NOT EXISTS foo2@test IDENTIFIED BY 'password';
Query OK, 0 rows affected, 1 warning (0.00 sec)

SHOW WARNINGS;
+-------+------+----------------------------------------------------+
| Level | Code | Message                                            |
+-------+------+----------------------------------------------------+
| Note  | 1973 | Can't create user 'foo2'@'test'; it already exists |
+-------+------+----------------------------------------------------+

Authentication Options

IDENTIFIED BY 'password'

The optional IDENTIFIED BY clause can be used to provide an account with a password. The password should be specified in plain text. It will be hashed by the PASSWORD function prior to being stored in the mysql.user/mysql.global_priv_table table.

For example, if our password is mariadb, then we can create the user with:

CREATE USER foo2@test IDENTIFIED BY 'mariadb';

If you do not specify a password with the IDENTIFIED BY clause, the user will be able to connect without a password. A blank password is not a wildcard to match any password. The user must connect without providing a password if no password is set.

The only authentication plugins that this clause supports are mysql_native_password and mysql_old_password.

IDENTIFIED BY PASSWORD 'password_hash'

The optional IDENTIFIED BY PASSWORD clause can be used to provide an account with a password that has already been hashed. The password should be specified as a hash that was provided by the PASSWORD function. It will be stored in the mysql.user/mysql.global_priv_table table as-is.

For example, if our password is mariadb, then we can find the hash with:

SELECT PASSWORD('mariadb');
+-------------------------------------------+
| PASSWORD('mariadb')                       |
+-------------------------------------------+
| *54958E764CE10E50764C2EECBB71D01F08549980 |
+-------------------------------------------+
1 row in set (0.00 sec)

And then we can create a user with the hash:

CREATE USER foo2@test IDENTIFIED BY PASSWORD '*54958E764CE10E50764C2EECBB71D01F08549980';

If you do not specify a password with the IDENTIFIED BY clause, the user will be able to connect without a password. A blank password is not a wildcard to match any password. The user must connect without providing a password if no password is set.

The only authentication plugins that this clause supports are mysql_native_password and mysql_old_password.

IDENTIFIED {VIA|WITH} authentication_plugin

The optional IDENTIFIED VIA authentication_plugin allows you to specify that the account should be authenticated by a specific authentication plugin. The plugin name must be an active authentication plugin as per SHOW PLUGINS. If it doesn't show up in that output, then you will need to install it with INSTALL PLUGIN or INSTALL SONAME.

For example, this could be used with the PAM authentication plugin:

CREATE USER foo2@test IDENTIFIED VIA pam;

Some authentication plugins allow additional arguments to be specified after a USING or AS keyword. For example, the PAM authentication plugin accepts a service name:

CREATE USER foo2@test IDENTIFIED VIA pam USING 'mariadb';

The exact meaning of the additional argument would depend on the specific authentication plugin.

MariaDB starting with 10.4.0

The USING or AS keyword can also be used to provide a plain-text password to a plugin if it's provided as an argument to the PASSWORD() function. This is only valid for authentication plugins that have implemented a hook for the PASSWORD() function. For example, the ed25519 authentication plugin supports this:

CREATE USER safe@'%' IDENTIFIED VIA ed25519 USING PASSWORD('secret');
MariaDB starting with 10.4.3

One can specify many authentication plugins, they all work as alternatives ways of authenticating a user:

CREATE USER safe@'%' IDENTIFIED VIA ed25519 USING PASSWORD('secret') OR unix_socket;

By default, when you create a user without specifying an authentication plugin, MariaDB uses the mysql_native_password plugin.

TLS Options

By default, MariaDB transmits data between the server and clients without encrypting it. This is generally acceptable when the server and client run on the same host or in networks where security is guaranteed through other means. However, in cases where the server and client exist on separate networks or they are in a high-risk network, the lack of encryption does introduce security concerns as a malicious actor could potentially eavesdrop on the traffic as it is sent over the network between them.

To mitigate this concern, MariaDB allows you to encrypt data in transit between the server and clients using the Transport Layer Security (TLS) protocol. TLS was formerly known as Secure Socket Layer (SSL), but strictly speaking the SSL protocol is a predecessor to TLS and, that version of the protocol is now considered insecure. The documentation still uses the term SSL often and for compatibility reasons TLS-related server system and status variables still use the prefix ssl_, but internally, MariaDB only supports its secure successors.

See Secure Connections Overview for more information about how to determine whether your MariaDB server has TLS support.

You can set certain TLS-related restrictions for specific user accounts. For instance, you might use this with user accounts that require access to sensitive data while sending it across networks that you do not control. These restrictions can be enabled for a user account with the CREATE USER, ALTER USER, or GRANT statements. The following options are available:

OptionDescription
REQUIRE NONETLS is not required for this account, but can still be used.
REQUIRE SSLThe account must use TLS, but no valid X509 certificate is required. This option cannot be combined with other TLS options.
REQUIRE X509The account must use TLS and must have a valid X509 certificate. This option implies REQUIRE SSL. This option cannot be combined with other TLS options.
REQUIRE ISSUER 'issuer'The account must use TLS and must have a valid X509 certificate. Also, the Certificate Authority must be the one specified via the string issuer. This option implies REQUIRE X509. This option can be combined with the SUBJECT, and CIPHER options in any order.
REQUIRE SUBJECT 'subject'The account must use TLS and must have a valid X509 certificate. Also, the certificate's Subject must be the one specified via the string subject. This option implies REQUIRE X509. This option can be combined with the ISSUER, and CIPHER options in any order.
REQUIRE CIPHER 'cipher'The account must use TLS, but no valid X509 certificate is required. Also, the encryption used for the connection must use a specific cipher method specified in the string cipher. This option implies REQUIRE SSL. This option can be combined with the ISSUER, and SUBJECT options in any order.

The REQUIRE keyword must be used only once for all specified options, and the AND keyword can be used to separate individual options, but it is not required.

For example, you can create a user account that requires these TLS options with the following:

CREATE USER 'alice'@'%'
    REQUIRE SUBJECT '/CN=alice/O=My Dom, Inc./C=US/ST=Oregon/L=Portland'
    AND ISSUER '/C=FI/ST=Somewhere/L=City/ O=Some Company/CN=Peter Parker/emailAddress=p.parker@marvel.com'
    AND CIPHER 'SHA-DES-CBC3-EDH-RSA';

If any of these options are set for a specific user account, then any client who tries to connect with that user account will have to be configured to connect with TLS.

See Securing Connections for Client and Server for information on how to enable TLS on the client and server.

Resource Limit Options

MariaDB starting with 10.2.0

MariaDB 10.2.0 introduced a number of resource limit options.

It is possible to set per-account limits for certain server resources. The following table shows the values that can be set per account:

Limit TypeDecription
MAX_QUERIES_PER_HOURNumber of statements that the account can issue per hour (including updates)
MAX_UPDATES_PER_HOURNumber of updates (not queries) that the account can issue per hour
MAX_CONNECTIONS_PER_HOURNumber of connections that the account can start per hour
MAX_USER_CONNECTIONSNumber of simultaneous connections that can be accepted from the same account; if it is 0, max_connections will be used instead; if max_connections is 0, there is no limit for this account's simultaneous connections.
MAX_STATEMENT_TIMETimeout, in seconds, for statements executed by the user. See also Aborting Statements that Exceed a Certain Time to Execute.

If any of these limits are set to 0, then there is no limit for that resource for that user.

Here is an example showing how to create a user with resource limits:

CREATE USER 'someone'@'localhost' WITH
    MAX_USER_CONNECTIONS 10
    MAX_QUERIES_PER_HOUR 200;

The resources are tracked per account, which means 'user'@'server'; not per user name or per connection.

The count can be reset for all users using FLUSH USER_RESOURCES, FLUSH PRIVILEGES or mysqladmin reload.

Per account resource limits are stored in the user table, in the mysql database. Columns used for resources limits are named max_questions, max_updates, max_connections (for MAX_CONNECTIONS_PER_HOUR), and max_user_connections (for MAX_USER_CONNECTIONS).

Account Names

Account names have both a user name component and a host name component, and are specified as 'user_name'@'host_name'.

The user name and host name may be unquoted, quoted as strings using double quotes (") or single quotes ('), or quoted as identifiers using backticks (`). You must use quotes when using special characters (such as a hyphen) or wildcard characters. If you quote, you must quote the user name and host name separately (for example 'user_name'@'host_name').

Host Name Component

If the host name is not provided, it is assumed to be '%'.

Host names may contain the wildcard characters % and _. They are matched as if by the LIKE clause. If you need to use a wildcard character literally (for example, to match a domain name with an underscore), prefix the character with a backslash. See LIKE for more information on escaping wildcard characters.

Host name matches are case-insensitive. Host names can match either domain names or IP addresses. Use 'localhost' as the host name to allow only local client connections.

You can use a netmask to match a range of IP addresses using 'base_ip/netmask' as the host name. A user with an IP address ip_addr will be allowed to connect if the following condition is true:

ip_addr & netmask = base_ip

For example, given a user:

CREATE USER 'maria'@'247.150.130.0/255.255.255.0';

the IP addresses satisfying this condition range from 247.150.130.0 to 247.150.130.255.

Using 255.255.255.255 is equivalent to not using a netmask at all. Netmasks cannot be used for IPv6 addresses.

Note that the credentials added when creating a user with the '%' wildcard host will not grant access in all cases. For example, some systems come with an anonymous localhost user, and when connecting from localhost this will take precedence.

Before MariaDB 10.6, the host name component could be up to 60 characters in length. Starting from MariaDB 10.6, it can be up to 255 characters.

User Name Component

User names must match exactly, including case. A user name that is empty is known as an anonymous account and is allowed to match a login attempt with any user name component. These are described more in the next section.

For valid identifiers to use as user names, see Identifier Names.

It is possible for more than one account to match when a user connects. MariaDB selects the first matching account after sorting according to the following criteria:

  • Accounts with an exact host name are sorted before accounts using a wildcard in the host name. Host names using a netmask are considered to be exact for sorting.
  • Accounts with a wildcard in the host name are sorted according to the position of the first wildcard character. Those with a wildcard character later in the host name sort before those with a wildcard character earlier in the host name.
  • Accounts with a non-empty user name sort before accounts with an empty user name.
  • Accounts with an empty user name are sorted last. As mentioned previously, these are known as anonymous accounts. These are described more in the next section.

The following table shows a list of example account as sorted by these criteria:

+---------+-------------+
| User    | Host        |
+---------+-------------+
| joffrey | 192.168.0.3 |
|         | 192.168.0.% |
| joffrey | 192.168.%   |
|         | 192.168.%   |
+---------+-------------+

Once connected, you only have the privileges granted to the account that matched, not all accounts that could have matched. For example, consider the following commands:

CREATE USER 'joffrey'@'192.168.0.3';
CREATE USER 'joffrey'@'%';
GRANT SELECT ON test.t1 to 'joffrey'@'192.168.0.3';
GRANT SELECT ON test.t2 to 'joffrey'@'%';

If you connect as joffrey from 192.168.0.3, you will have the SELECT privilege on the table test.t1, but not on the table test.t2. If you connect as joffrey from any other IP address, you will have the SELECT privilege on the table test.t2, but not on the table test.t1.

Usernames can be up to 80 characters long before 10.6 and starting from 10.6 it can be 128 characters long.

Anonymous Accounts

Anonymous accounts are accounts where the user name portion of the account name is empty. These accounts act as special catch-all accounts. If a user attempts to log into the system from a host, and an anonymous account exists with a host name portion that matches the user's host, then the user will log in as the anonymous account if there is no more specific account match for the user name that the user entered.

For example, here are some anonymous accounts:

CREATE USER ''@'localhost';
CREATE USER ''@'192.168.0.3';

Fixing a Legacy Default Anonymous Account

On some systems, the mysql.db table has some entries for the ''@'%' anonymous account by default. Unfortunately, there is no matching entry in the mysql.user/mysql.global_priv_table table, which means that this anonymous account doesn't exactly exist, but it does have privileges--usually on the default test database created by mysql_install_db. These account-less privileges are a legacy that is leftover from a time when MySQL's privilege system was less advanced.

This situation means that you will run into errors if you try to create a ''@'%' account. For example:

CREATE USER ''@'%';
ERROR 1396 (HY000): Operation CREATE USER failed for ''@'%'

The fix is to DELETE the row in the mysql.db table and then execute FLUSH PRIVILEGES:

DELETE FROM mysql.db WHERE User='' AND Host='%';
FLUSH PRIVILEGES;

And then the account can be created:

CREATE USER ''@'%';
Query OK, 0 rows affected (0.01 sec)

See MDEV-13486 for more information.

Password Expiry

MariaDB starting with 10.4.3

Besides automatic password expiry, as determined by default_password_lifetime, password expiry times can be set on an individual user basis, overriding the global setting, for example:

CREATE USER 'monty'@'localhost' PASSWORD EXPIRE INTERVAL 120 DAY;

See User Password Expiry for more details.

Account Locking

MariaDB starting with 10.4.2

Account locking permits privileged administrators to lock/unlock user accounts. No new client connections will be permitted if an account is locked (existing connections are not affected). For example:

CREATE USER 'marijn'@'localhost' ACCOUNT LOCK;

See Account Locking for more details.

From MariaDB 10.4.7 and MariaDB 10.5.8, the lock_option and password_option clauses can occur in either order.

See Also

1.1.1.1.2 ALTER USER

MariaDB starting with 10.2.0

The ALTER USER statement was introduced in MariaDB 10.2.0.

Syntax

ALTER USER [IF EXISTS] 
 user_specification [,user_specification] ...
  [REQUIRE {NONE | tls_option [[AND] tls_option] ...}]
  [WITH resource_option [resource_option] ...]
  [lock_option] [password_option] 

user_specification:
  username [authentication_option]

authentication_option:
  IDENTIFIED BY 'password' 
  | IDENTIFIED BY PASSWORD 'password_hash'
  | IDENTIFIED {VIA|WITH} authentication_rule [OR authentication_rule] ... 
 
authentication_rule:
  authentication_plugin
  | authentication_plugin {USING|AS} 'authentication_string'
  | authentication_plugin {USING|AS} PASSWORD('password')

tls_option
  SSL 
  | X509
  | CIPHER 'cipher'
  | ISSUER 'issuer'
  | SUBJECT 'subject'

resource_option
  MAX_QUERIES_PER_HOUR count
  | MAX_UPDATES_PER_HOUR count
  | MAX_CONNECTIONS_PER_HOUR count
  | MAX_USER_CONNECTIONS count
  | MAX_STATEMENT_TIME time

password_option:
  PASSWORD EXPIRE
  | PASSWORD EXPIRE DEFAULT
  | PASSWORD EXPIRE NEVER
  | PASSWORD EXPIRE INTERVAL N DAY

lock_option:
    ACCOUNT LOCK
  | ACCOUNT UNLOCK
}

Contents

  1. Syntax
  2. Description
  3. IF EXISTS
  4. Account Names
  5. Authentication Options
    1. IDENTIFIED BY 'password'
    2. IDENTIFIED BY PASSWORD 'password_hash'
    3. IDENTIFIED {VIA|WITH} authentication_plugin
  6. TLS Options
  7. Resource Limit Options
  8. Password Expiry
  9. Account Locking
  10. See Also

Description

The ALTER USER statement modifies existing MariaDB accounts. To use it, you must have the global CREATE USER privilege or the UPDATE privilege for the mysql database. The global SUPER privilege is also required if the read_only system variable is enabled.

If any of the specified user accounts do not yet exist, an error results. If an error occurs, ALTER USER will still modify the accounts that do not result in an error. Only one error is produced for all users which have not been modified.

IF EXISTS

When the IF EXISTS clause is used, MariaDB will return a warning instead of an error for each specified user that does not exist.

Account Names

For ALTER USER statements, account names are specified as the username argument in the same way as they are for CREATE USER statements. See account names from the CREATE USER page for details on how account names are specified.

CURRENT_USER or CURRENT_USER() can also be used to alter the account logged into the current session. For example, to change the current user's password to mariadb:

ALTER USER CURRENT_USER() IDENTIFIED BY 'mariadb';

Authentication Options

MariaDB starting with 10.4

From MariaDB 10.4, it is possible to use more than one authentication plugin for each user account. For example, this can be useful to slowly migrate users to the more secure ed25519 authentication plugin over time, while allowing the old mysql_native_password authentication plugin as an alternative for the transitional period. See Authentication from MariaDB 10.4 for more.

When running ALTER USER, not specifying an authentication option in the IDENTIFIED VIA clause will remove that authentication method. (However this was not the case before MariaDB 10.4.13, see MDEV-21928)

For example, a user is created with the ability to authenticate via both a password and unix_socket:

CREATE USER 'bob'@'localhost' 
  IDENTIFIED VIA mysql_native_password USING PASSWORD('pwd') 
  OR unix_socket;

SHOW CREATE USER 'bob'@'localhost'\G
*************************** 1. row ***************************
CREATE USER for bob@localhost: CREATE USER `bob`@`localhost` 
  IDENTIFIED VIA mysql_native_password 
  USING '*975B2CD4FF9AE554FE8AD33168FBFC326D2021DD' 
  OR unix_socket

If the user's password is updated, but unix_socket authentication is not specified in the IDENTIFIED VIA clause, unix_socket authentication will no longer be permitted.

ALTER USER 'bob'@'localhost' IDENTIFIED VIA mysql_native_password 
  USING PASSWORD('pwd2');

SHOW CREATE USER 'bob'@'localhost'\G
*************************** 1. row ***************************
CREATE USER for bob@localhost: CREATE USER `bob`@`localhost` 
  IDENTIFIED BY PASSWORD '*38366FDA01695B6A5A9DD4E428D9FB8F7EB75512'

IDENTIFIED BY 'password'

The optional IDENTIFIED BY clause can be used to provide an account with a password. The password should be specified in plain text. It will be hashed by the PASSWORD function prior to being stored to the mysql.user table.

For example, if our password is mariadb, then we can set the account's password with:

ALTER USER foo2@test IDENTIFIED BY 'mariadb';

If you do not specify a password with the IDENTIFIED BY clause, the user will be able to connect without a password. A blank password is not a wildcard to match any password. The user must connect without providing a password if no password is set.

The only authentication plugins that this clause supports are mysql_native_password and mysql_old_password.

IDENTIFIED BY PASSWORD 'password_hash'

The optional IDENTIFIED BY PASSWORD clause can be used to provide an account with a password that has already been hashed. The password should be specified as a hash that was provided by the PASSWORD#function. It will be stored to the mysql.user table as-is.

For example, if our password is mariadb, then we can find the hash with:

SELECT PASSWORD('mariadb');
+-------------------------------------------+
| PASSWORD('mariadb')                       |
+-------------------------------------------+
| *54958E764CE10E50764C2EECBB71D01F08549980 |
+-------------------------------------------+

And then we can set an account's password with the hash:

ALTER USER foo2@test 
  IDENTIFIED BY PASSWORD '*54958E764CE10E50764C2EECBB71D01F08549980';

If you do not specify a password with the IDENTIFIED BY clause, the user will be able to connect without a password. A blank password is not a wildcard to match any password. The user must connect without providing a password if no password is set.

The only authentication plugins that this clause supports are mysql_native_password and mysql_old_password.

IDENTIFIED {VIA|WITH} authentication_plugin

The optional IDENTIFIED VIA authentication_plugin allows you to specify that the account should be authenticated by a specific authentication plugin. The plugin name must be an active authentication plugin as per SHOW PLUGINS. If it doesn't show up in that output, then you will need to install it with INSTALL PLUGIN or INSTALL SONAME.

For example, this could be used with the PAM authentication plugin:

ALTER USER foo2@test IDENTIFIED VIA pam;

Some authentication plugins allow additional arguments to be specified after a USING or AS keyword. For example, the PAM authentication plugin accepts a service name:

ALTER USER foo2@test IDENTIFIED VIA pam USING 'mariadb';

The exact meaning of the additional argument would depend on the specific authentication plugin.

In MariaDB 10.4 and later, the USING or AS keyword can also be used to provide a plain-text password to a plugin if it's provided as an argument to the PASSWORD() function. This is only valid for authentication plugins that have implemented a hook for the PASSWORD() function. For example, the ed25519 authentication plugin supports this:

ALTER USER safe@'%' IDENTIFIED VIA ed25519 USING PASSWORD('secret');

TLS Options

By default, MariaDB transmits data between the server and clients without encrypting it. This is generally acceptable when the server and client run on the same host or in networks where security is guaranteed through other means. However, in cases where the server and client exist on separate networks or they are in a high-risk network, the lack of encryption does introduce security concerns as a malicious actor could potentially eavesdrop on the traffic as it is sent over the network between them.

To mitigate this concern, MariaDB allows you to encrypt data in transit between the server and clients using the Transport Layer Security (TLS) protocol. TLS was formerly known as Secure Socket Layer (SSL), but strictly speaking the SSL protocol is a predecessor to TLS and, that version of the protocol is now considered insecure. The documentation still uses the term SSL often and for compatibility reasons TLS-related server system and status variables still use the prefix ssl_, but internally, MariaDB only supports its secure successors.

See Secure Connections Overview for more information about how to determine whether your MariaDB server has TLS support.

You can set certain TLS-related restrictions for specific user accounts. For instance, you might use this with user accounts that require access to sensitive data while sending it across networks that you do not control. These restrictions can be enabled for a user account with the CREATE USER, ALTER USER, or GRANT statements. The following options are available:

OptionDescription
REQUIRE NONETLS is not required for this account, but can still be used.
REQUIRE SSLThe account must use TLS, but no valid X509 certificate is required. This option cannot be combined with other TLS options.
REQUIRE X509The account must use TLS and must have a valid X509 certificate. This option implies REQUIRE SSL. This option cannot be combined with other TLS options.
REQUIRE ISSUER 'issuer'The account must use TLS and must have a valid X509 certificate. Also, the Certificate Authority must be the one specified via the string issuer. This option implies REQUIRE X509. This option can be combined with the SUBJECT, and CIPHER options in any order.
REQUIRE SUBJECT 'subject'The account must use TLS and must have a valid X509 certificate. Also, the certificate's Subject must be the one specified via the string subject. This option implies REQUIRE X509. This option can be combined with the ISSUER, and CIPHER options in any order.
REQUIRE CIPHER 'cipher'The account must use TLS, but no valid X509 certificate is required. Also, the encryption used for the connection must use a specific cipher method specified in the string cipher. This option implies REQUIRE SSL. This option can be combined with the ISSUER, and SUBJECT options in any order.

The REQUIRE keyword must be used only once for all specified options, and the AND keyword can be used to separate individual options, but it is not required.

For example, you can alter a user account to require these TLS options with the following:

ALTER USER 'alice'@'%'
    REQUIRE SUBJECT '/CN=alice/O=My Dom, Inc./C=US/ST=Oregon/L=Portland'
    AND ISSUER '/C=FI/ST=Somewhere/L=City/ O=Some Company/CN=Peter Parker/emailAddress=p.parker@marvel.com'
    AND CIPHER 'SHA-DES-CBC3-EDH-RSA';

If any of these options are set for a specific user account, then any client who tries to connect with that user account will have to be configured to connect with TLS.

See Securing Connections for Client and Server for information on how to enable TLS on the client and server.

Resource Limit Options

MariaDB starting with 10.2.0

MariaDB 10.2.0 introduced a number of resource limit options.

It is possible to set per-account limits for certain server resources. The following table shows the values that can be set per account:

Limit TypeDecription
MAX_QUERIES_PER_HOURNumber of statements that the account can issue per hour (including updates)
MAX_UPDATES_PER_HOURNumber of updates (not queries) that the account can issue per hour
MAX_CONNECTIONS_PER_HOURNumber of connections that the account can start per hour
MAX_USER_CONNECTIONSNumber of simultaneous connections that can be accepted from the same account; if it is 0, max_connections will be used instead; if max_connections is 0, there is no limit for this account's simultaneous connections.
MAX_STATEMENT_TIMETimeout, in seconds, for statements executed by the user. See also Aborting Statements that Exceed a Certain Time to Execute.

If any of these limits are set to 0, then there is no limit for that resource for that user.

Here is an example showing how to set an account's resource limits:

ALTER USER 'someone'@'localhost' WITH
    MAX_USER_CONNECTIONS 10
    MAX_QUERIES_PER_HOUR 200;

The resources are tracked per account, which means 'user'@'server'; not per user name or per connection.

The count can be reset for all users using FLUSH USER_RESOURCES, FLUSH PRIVILEGES or mysqladmin reload.

Per account resource limits are stored in the user table, in the mysql database. Columns used for resources limits are named max_questions, max_updates, max_connections (for MAX_CONNECTIONS_PER_HOUR), and max_user_connections (for MAX_USER_CONNECTIONS).

Password Expiry

MariaDB starting with 10.4.3

Besides automatic password expiry, as determined by default_password_lifetime, password expiry times can be set on an individual user basis, overriding the global setting, for example:

ALTER USER 'monty'@'localhost' PASSWORD EXPIRE INTERVAL 120 DAY;
ALTER USER 'monty'@'localhost' PASSWORD EXPIRE NEVER;
ALTER USER 'monty'@'localhost' PASSWORD EXPIRE DEFAULT;

See User Password Expiry for more details.

Account Locking

MariaDB starting with 10.4.2

Account locking permits privileged administrators to lock/unlock user accounts. No new client connections will be permitted if an account is locked (existing connections are not affected). For example:

ALTER USER 'marijn'@'localhost' ACCOUNT LOCK;

See Account Locking for more details.

From MariaDB 10.4.7 and MariaDB 10.5.8, the lock_option and password_option clauses can occur in either order.

See Also

1.1.1.1.3 DROP USER

Syntax

DROP USER [IF EXISTS] user_name [, user_name] ...

Contents

  1. Syntax
  2. Description
    1. IF EXISTS
  3. Examples
  4. See Also

Description

The DROP USER statement removes one or more MariaDB accounts. It removes privilege rows for the account from all grant tables. To use this statement, you must have the global CREATE USER privilege or the DELETE privilege for the mysql database. Each account is named using the same format as for the CREATE USER statement; for example, 'jeffrey'@'localhost'. If you specify only the user name part of the account name, a host name part of '%' is used. For additional information about specifying account names, see CREATE USER.

Note that, if you specify an account that is currently connected, it will not be deleted until the connection is closed. The connection will not be automatically closed.

If any of the specified user accounts do not exist, ERROR 1396 (HY000) results. If an error occurs, DROP USER will still drop the accounts that do not result in an error. Only one error is produced for all users which have not been dropped:

ERROR 1396 (HY000): Operation DROP USER failed for 'u1'@'%','u2'@'%'

Failed CREATE or DROP operations, for both users and roles, produce the same error code.

IF EXISTS

If the IF EXISTS clause is used, MariaDB will return a note instead of an error if the user does not exist.

Examples

DROP USER bob;

IF EXISTS:

DROP USER bob;
ERROR 1396 (HY000): Operation DROP USER failed for 'bob'@'%'

DROP USER IF EXISTS bob;
Query OK, 0 rows affected, 1 warning (0.00 sec)

SHOW WARNINGS;
+-------+------+---------------------------------------------+
| Level | Code | Message                                     |
+-------+------+---------------------------------------------+
| Note  | 1974 | Can't drop user 'bob'@'%'; it doesn't exist |
+-------+------+---------------------------------------------+

See Also

1.1.1.1.4 GRANT

Contents

  1. Syntax
  2. Description
  3. Account Names
  4. Implicit Account Creation
  5. Privilege Levels
    1. The USAGE Privilege
    2. The ALL PRIVILEGES Privilege
    3. The GRANT OPTION Privilege
    4. Global Privileges
      1. BINLOG ADMIN
      2. BINLOG MONITOR
      3. BINLOG REPLAY
      4. CONNECTION ADMIN
      5. CREATE USER
      6. FEDERATED ADMIN
      7. FILE
      8. GRANT OPTION
      9. PROCESS
      10. READ_ONLY ADMIN
      11. RELOAD
      12. REPLICATION CLIENT
      13. REPLICATION MASTER ADMIN
      14. REPLICA MONITOR
      15. REPLICATION REPLICA
      16. REPLICATION SLAVE
      17. REPLICATION SLAVE ADMIN
      18. SET USER
      19. SHOW DATABASES
      20. SHUTDOWN
      21. SUPER
    5. Database Privileges
    6. Table Privileges
    7. Column Privileges
    8. Function Privileges
    9. Procedure Privileges
    10. Proxy Privileges
  6. Authentication Options
    1. IDENTIFIED BY 'password'
    2. IDENTIFIED BY PASSWORD 'password_hash'
    3. IDENTIFIED {VIA|WITH} authentication_plugin
  7. Resource Limit Options
  8. TLS Options
  9. Roles
    1. Syntax
  10. Grant Examples
    1. Granting Root-like Privileges
  11. See Also

Syntax

GRANT
    priv_type [(column_list)]
      [, priv_type [(column_list)]] ...
    ON [object_type] priv_level
    TO user_specification [ user_options ...]

user_specification:
  username [authentication_option]

authentication_option:
  IDENTIFIED BY 'password' 
  | IDENTIFIED BY PASSWORD 'password_hash'
  | IDENTIFIED {VIA|WITH} authentication_rule [OR authentication_rule  ...]

authentication_rule:
    authentication_plugin
  | authentication_plugin {USING|AS} 'authentication_string'
  | authentication_plugin {USING|AS} PASSWORD('password')

GRANT PROXY ON username
    TO user_specification [, user_specification ...]
    [WITH GRANT OPTION]

GRANT rolename TO grantee [, grantee ...]
    [WITH ADMIN OPTION]

grantee:
    rolename
    username [authentication_option]

user_options:
    [REQUIRE {NONE | tls_option [[AND] tls_option] ...}]
    [WITH with_option [with_option] ...]

object_type:
    TABLE
  | FUNCTION
  | PROCEDURE
  | PACKAGE

priv_level:
    *
  | *.*
  | db_name.*
  | db_name.tbl_name
  | tbl_name
  | db_name.routine_name

with_option:
    GRANT OPTION
  | resource_option

resource_option:
  MAX_QUERIES_PER_HOUR count
  | MAX_UPDATES_PER_HOUR count
  | MAX_CONNECTIONS_PER_HOUR count
  | MAX_USER_CONNECTIONS count
  | MAX_STATEMENT_TIME time

tls_option:
  SSL 
  | X509
  | CIPHER 'cipher'
  | ISSUER 'issuer'
  | SUBJECT 'subject'

Description

The GRANT statement allows you to grant privileges or roles to accounts. To use GRANT, you must have the GRANT OPTION privilege, and you must have the privileges that you are granting.

Use the REVOKE statement to revoke privileges granted with the GRANT statement.

Use the SHOW GRANTS statement to determine what privileges an account has.

Account Names

For GRANT statements, account names are specified as the username argument in the same way as they are for CREATE USER statements. See account names from the CREATE USER page for details on how account names are specified.

Implicit Account Creation

The GRANT statement also allows you to implicitly create accounts in some cases.

If the account does not yet exist, then GRANT can implicitly create it. To implicitly create an account with GRANT, a user is required to have the same privileges that would be required to explicitly create the account with the CREATE USER statement.

If the NO_AUTO_CREATE_USER SQL_MODE is set, then accounts can only be created if authentication information is specified, or with a CREATE USER statement. If no authentication information is provided, GRANT will produce an error when the specified account does not exist, for example:

show variables like '%sql_mode%' ;
+---------------+--------------------------------------------+
| Variable_name | Value                                      |
+---------------+--------------------------------------------+
| sql_mode      | NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION |
+---------------+--------------------------------------------+

GRANT USAGE ON *.* TO 'user123'@'%' IDENTIFIED BY '';
ERROR 1133 (28000): Can't find any matching row in the user table

GRANT USAGE ON *.* TO 'user123'@'%' IDENTIFIED VIA PAM using 'mariadb' require ssl ;
Query OK, 0 rows affected (0.00 sec)
 
select host, user from mysql.user where user='user123' ;

+------+----------+
| host | user     |
+------+----------+
| %    | user123 |
+------+----------+

Privilege Levels

Privileges can be set globally, for an entire database, for a table or routine, or for individual columns in a table. Certain privileges can only be set at certain levels.

  • Global privileges priv_type are granted using *.* for priv_level. Global privileges include privileges to administer the database and manage user accounts, as well as privileges for all tables, functions, and procedures. Global privileges are stored in the mysql.user table.
  • Database privileges priv_type are granted using db_name.* for priv_level, or using just * to use default database. Database privileges include privileges to create tables and functions, as well as privileges for all tables, functions, and procedures in the database. Database privileges are stored in the mysql.db table.
  • Table privileges priv_type are granted using db_name.tbl_name for priv_level, or using just tbl_name to specify a table in the default database. The TABLE keyword is optional. Table privileges include the ability to select and change data in the table. Certain table privileges can be granted for individual columns.
  • Column privileges priv_type are granted by specifying a table for priv_level and providing a column list after the privilege type. They allow you to control exactly which columns in a table users can select and change.
  • Function privileges priv_type are granted using FUNCTION db_name.routine_name for priv_level, or using just FUNCTION routine_name to specify a function in the default database.
  • Procedure privileges priv_type are granted using PROCEDURE db_name.routine_name for priv_level, or using just PROCEDURE routine_name to specify a procedure in the default database.

The USAGE Privilege

The USAGE privilege grants no real privileges. The SHOW GRANTS statement will show a global USAGE privilege for a newly-created user. You can use USAGE with the GRANT statement to change options like GRANT OPTION and MAX_USER_CONNECTIONS without changing any account privileges.

The ALL PRIVILEGES Privilege

The ALL PRIVILEGES privilege grants all available privileges. Granting all privileges only affects the given privilege level. For example, granting all privileges on a table does not grant any privileges on the database or globally.

Using ALL PRIVILEGES does not grant the special GRANT OPTION privilege.

You can use ALL instead of ALL PRIVILEGES.

The GRANT OPTION Privilege

Use the WITH GRANT OPTION clause to give users the ability to grant privileges to other users at the given privilege level. Users with the GRANT OPTION privilege can only grant privileges they have. They cannot grant privileges at a higher privilege level than they have the GRANT OPTION privilege.

The GRANT OPTION privilege cannot be set for individual columns. If you use WITH GRANT OPTION when specifying column privileges, the GRANT OPTION privilege will be granted for the entire table.

Using the WITH GRANT OPTION clause is equivalent to listing GRANT OPTION as a privilege.

Global Privileges

The following table lists the privileges that can be granted globally. You can also grant all database, table, and function privileges globally. When granted globally, these privileges apply to all databases, tables, or functions, including those created later.

To set a global privilege, use *.* for priv_level.

BINLOG ADMIN

Enables administration of the binary log, including the PURGE BINARY LOGS statement and setting the binlog_annotate_row_events, binlog_cache_size, binlog_commit_wait_count, binlog_commit_wait_usec, binlog_direct_non_transactional_updates, binlog_expire_logs_seconds, binlog_file_cache_size, binlog_format, binlog_row_image, binlog_row_metadata, binlog_stmt_cache_size, expire_logs_days, log_bin_compress, log_bin_compress_min_len, log_bin_trust_function_creators, max_binlog_cache_size, max_binlog_size, max_binlog_stmt_cache_size, sql_log_bin and sync_binlog system variables. Added in MariaDB 10.5.2.

BINLOG MONITOR

New name for REPLICATION CLIENT from MariaDB 10.5.2, (REPLICATION CLIENT still supported as an alias for compatibility purposes). Permits running SHOW commands related to the binary log, in particular the SHOW BINLOG STATUS, SHOW REPLICA STATUS and SHOW BINARY LOGS statements.

BINLOG REPLAY

Enables replaying the binary log with the BINLOG statement (generated by mariadb-binlog), executing SET timestamp when secure_timestamp is set to replication, and setting the session values of system variables usually included in BINLOG output, in particular gtid_domain_id, gtid_seq_no, pseudo_thread_id and server_id. Added in MariaDB 10.5.2

CONNECTION ADMIN

Enables administering connection resource limit options. This includes ignoring the limits specified by max_connections, max_user_connections and max_password_errors, not executing the statements specified in init_connect, killing connections and queries owned by other users as well as setting the following connection-related system variables: connect_timeout, disconnect_on_expired_password, extra_max_connections, init_connect, max_connections, max_connect_errors, max_password_errors, proxy_protocol_networks, secure_auth, slow_launch_time, thread_pool_exact_stats, thread_pool_dedicated_listener, thread_pool_idle_timeout, thread_pool_max_threads, thread_pool_min_threads, thread_pool_mode, thread_pool_oversubscribe, thread_pool_prio_kickup_timer, thread_pool_priority, thread_pool_size, thread_pool_stall_limit. Added in MariaDB 10.5.2.

CREATE USER

Create a user using the CREATE USER statement, or implicitly create a user with the GRANT statement.

FEDERATED ADMIN

Execute CREATE SERVER, ALTER SERVER, and DROP SERVER statements. Added in MariaDB 10.5.2.

FILE

Read and write files on the server, using statements like LOAD DATA INFILE or functions like LOAD_FILE(). Also needed to create CONNECT outward tables. MariaDB server must have the permissions to access those files.

GRANT OPTION

Grant global privileges. You can only grant privileges that you have.

PROCESS

Show information about the active processes, for example via SHOW PROCESSLIST or mysqladmin processlist. If you have the PROCESS privilege, you can see all threads. Otherwise, you can see only your own threads (that is, threads associated with the MariaDB account that you are using).

READ_ONLY ADMIN

User can set the read_only system variable and allows the user to perform write operations, even when the read_only option is active. Added in MariaDB 10.5.2.

RELOAD

Execute FLUSH statements or equivalent mariadb-admin/mysqladmin commands.

REPLICATION CLIENT

Execute SHOW MASTER STATUS, SHOW SLAVE STATUS and SHOW BINARY LOGS informative statements. Renamed to BINLOG MONITOR in MariaDB 10.5.2 (but still supported as an alias for compatibility reasons).

REPLICATION MASTER ADMIN

Permits administration of primary servers, including the SHOW REPLICA HOSTS statement, and setting the gtid_binlog_state, gtid_domain_id, master_verify_checksum and server_id system variables. Added in MariaDB 10.5.2.

REPLICA MONITOR

Permit SHOW REPLICA STATUS and SHOW RELAYLOG EVENTS. From MariaDB 10.5.9.

When a user would upgrade from an older major release to a MariaDB 10.5 minor release prior to MariaDB 10.5.9, certain user accounts would lose capabilities. For example, a user account that had the REPLICATION CLIENT privilege in older major releases could run SHOW REPLICA STATUS, but after upgrading to a MariaDB 10.5 minor release prior to MariaDB 10.5.9, they could no longer run SHOW REPLICA STATUS, because that statement was changed to require the REPLICATION REPLICA ADMIN privilege.

This issue is fixed in MariaDB 10.5.9 with this new privilege, which now grants the user the ability to execute SHOW [ALL] (SLAVE | REPLICA) STATUS.

When a database is upgraded from an older major release to MariaDB Server 10.5.9 or later, any user accounts with the REPLICATION CLIENT or REPLICATION SLAVE privileges will automatically be granted the new REPLICA MONITOR privilege. The privilege fix occurs when the server is started up, not when mariadb-upgrade is performed.

However, when a database is upgraded from an early 10.5 minor release to 10.5.9 and later, the user will have to fix any user account privileges manually.

REPLICATION REPLICA

Synonym for REPLICATION SLAVE. From MariaDB 10.5.1.

REPLICATION SLAVE

Accounts used by replica servers on the primary need this privilege. This is needed to get the updates made on the master. From MariaDB 10.5.1, REPLICATION REPLICA is an alias for REPLICATION SLAVE.

REPLICATION SLAVE ADMIN

Permits administering replica servers, including START REPLICA/SLAVE, STOP REPLICA/SLAVE, CHANGE MASTER, SHOW REPLICA/SLAVE STATUS, SHOW RELAYLOG EVENTS statements, replaying the binary log with the BINLOG statement (generated by mariadb-binlog), and setting the gtid_cleanup_batch_size, gtid_ignore_duplicates, gtid_pos_auto_engines, gtid_slave_pos, gtid_strict_mode, init_slave, read_binlog_speed_limit, relay_log_purge, relay_log_recovery, replicate_do_db, replicate_do_table, replicate_events_marked_for_skip, replicate_ignore_db, replicate_ignore_table, replicate_wild_do_table, replicate_wild_ignore_table, slave_compressed_protocol, slave_ddl_exec_mode, slave_domain_parallel_threads, slave_exec_mode, slave_max_allowed_packet, slave_net_timeout, slave_parallel_max_queued, slave_parallel_mode, slave_parallel_threads, slave_parallel_workers, slave_run_triggers_for_rbr, slave_sql_verify_checksum, slave_transaction_retry_interval, slave_type_conversions, sync_master_info, sync_relay_log and sync_relay_log_info system variables. Added in MariaDB 10.5.2.

SET USER

Enables setting the DEFINER when creating triggers, views, stored functions and stored procedures. Added in MariaDB 10.5.2.

SHOW DATABASES

List all databases using the SHOW DATABASES statement. Without the SHOW DATABASES privilege, you can still issue the SHOW DATABASES statement, but it will only list databases containing tables on which you have privileges.

SHUTDOWN

Shut down the server using SHUTDOWN or the mysqladmin shutdown command.

SUPER

Execute superuser statements: CHANGE MASTER TO, KILL (users who do not have this privilege can only KILL their own threads), PURGE LOGS, SET global system variables, or the mysqladmin debug command. Also, this permission allows the user to write data even if the read_only startup option is set, enable or disable logging, enable or disable replication on replica, specify a DEFINER for statements that support that clause, connect once after reaching the MAX_CONNECTIONS. If a statement has been specified for the init-connect mysqld option, that command will not be executed when a user with SUPER privileges connects to the server.

The SUPER privilege has been split into multiple smaller privileges from MariaDB 10.5.2 to allow for more fine-grained privileges, although it remains an alias for these smaller privileges.

Database Privileges

The following table lists the privileges that can be granted at the database level. You can also grant all table and function privileges at the database level. Table and function privileges on a database apply to all tables or functions in that database, including those created later.

To set a privilege for a database, specify the database using db_name.* for priv_level, or just use * to specify the default database.

PrivilegeDescription
CREATECreate a database using the CREATE DATABASE statement, when the privilege is granted for a database. You can grant the CREATE privilege on databases that do not yet exist. This also grants the CREATE privilege on all tables in the database.
CREATE ROUTINECreate Stored Programs using the CREATE PROCEDURE and CREATE FUNCTION statements.
CREATE TEMPORARY TABLESCreate temporary tables with the CREATE TEMPORARY TABLE statement. This privilege enable writing and dropping those temporary tables
DROPDrop a database using the DROP DATABASE statement, when the privilege is granted for a database. This also grants the DROP privilege on all tables in the database.
EVENTCreate, drop and alter EVENTs.
GRANT OPTIONGrant database privileges. You can only grant privileges that you have.
LOCK TABLESAcquire explicit locks using the LOCK TABLES statement; you also need to have the SELECT privilege on a table, in order to lock it.

Table Privileges

PrivilegeDescription
ALTERChange the structure of an existing table using the ALTER TABLE statement.
CREATECreate a table using the CREATE TABLE statement. You can grant the CREATE privilege on tables that do not yet exist.
CREATE VIEWCreate a view using the CREATE_VIEW statement.
DELETERemove rows from a table using the DELETE statement.
DELETE HISTORYRemove historical rows from a table using the DELETE HISTORY statement. Displays as DELETE VERSIONING ROWS when running SHOW GRANTS until MariaDB 10.3.15 and until MariaDB 10.4.5 (MDEV-17655), or when running SHOW PRIVILEGES until MariaDB 10.5.2, MariaDB 10.4.13 and MariaDB 10.3.23 (MDEV-20382). From MariaDB 10.3.4. From MariaDB 10.3.5, if a user has the SUPER privilege but not this privilege, running mysql_upgrade will grant this privilege as well.
DROPDrop a table using the DROP TABLE statement or a view using the DROP VIEW statement. Also required to execute the TRUNCATE TABLE statement.
GRANT OPTIONGrant table privileges. You can only grant privileges that you have.
INDEXCreate an index on a table using the CREATE INDEX statement. Without the INDEX privilege, you can still create indexes when creating a table using the CREATE TABLE statement if the you have the CREATE privilege, and you can create indexes using the ALTER TABLE statement if you have the ALTER privilege.
INSERTAdd rows to a table using the INSERT statement. The INSERT privilege can also be set on individual columns; see Column Privileges below for details.
REFERENCESUnused.
SELECTRead data from a table using the SELECT statement. The SELECT privilege can also be set on individual columns; see Column Privileges below for details.
SHOW VIEWShow the CREATE VIEW statement to create a view using the SHOW CREATE VIEW statement.
TRIGGERExecute triggers associated to tables you update, execute the CREATE TRIGGER and DROP TRIGGER statements. You will still be able to see triggers.
UPDATEUpdate existing rows in a table using the UPDATE statement. UPDATE statements usually include a WHERE clause to update only certain rows. You must have SELECT privileges on the table or the appropriate columns for the WHERE clause. The UPDATE privilege can also be set on individual columns; see Column Privileges below for details.

Column Privileges

Some table privileges can be set for individual columns of a table. To use column privileges, specify the table explicitly and provide a list of column names after the privilege type. For example, the following statement would allow the user to read the names and positions of employees, but not other information from the same table, such as salaries.

GRANT SELECT (name, position) on Employee to 'jeffrey'@'localhost';
PrivilegeDescription
INSERT (column_list)Add rows specifying values in columns using the INSERT statement. If you only have column-level INSERT privileges, you must specify the columns you are setting in the INSERT statement. All other columns will be set to their default values, or NULL.
REFERENCES (column_list)Unused.
SELECT (column_list)Read values in columns using the SELECT statement. You cannot access or query any columns for which you do not have SELECT privileges, including in WHERE, ON, GROUP BY, and ORDER BY clauses.
UPDATE (column_list)Update values in columns of existing rows using the UPDATE statement. UPDATE statements usually include a WHERE clause to update only certain rows. You must have SELECT privileges on the table or the appropriate columns for the WHERE clause.

Function Privileges

PrivilegeDescription
ALTER ROUTINEChange the characteristics of a stored function using the ALTER FUNCTION statement.
EXECUTEUse a stored function. You need SELECT privileges for any tables or columns accessed by the function.
GRANT OPTIONGrant function privileges. You can only grant privileges that you have.

Procedure Privileges

PrivilegeDescription
ALTER ROUTINEChange the characteristics of a stored procedure using the ALTER PROCEDURE statement.
EXECUTEExecute a stored procedure using the CALL statement. The privilege to call a procedure may allow you to perform actions you wouldn't otherwise be able to do, such as insert rows into a table.
GRANT OPTIONGrant procedure privileges. You can only grant privileges that you have.

Proxy Privileges

PrivilegeDescription
PROXYPermits one user to be a proxy for another.

The PROXY privilege allows one user to proxy as another user, which means their privileges change to that of the proxy user, and the CURRENT_USER() function returns the user name of the proxy user.

The PROXY privilege only works with authentication plugins that support it. The default mysql_native_password authentication plugin does not support proxy users.

The pam authentication plugin is the only plugin included with MariaDB that currently supports proxy users. The PROXY privilege is commonly used with the pam authentication plugin to enable user and group mapping with PAM.

For example, to grant the PROXY privilege to an anonymous account that authenticates with the pam authentication plugin, you could execute the following:

CREATE USER 'dba'@'%' IDENTIFIED BY 'strongpassword';
GRANT ALL PRIVILEGES ON *.* TO 'dba'@'%' ;

CREATE USER ''@'%' IDENTIFIED VIA pam USING 'mariadb';
GRANT PROXY ON 'dba'@'%' TO ''@'%';

A user account can only grant the PROXY privilege for a specific user account if the granter also has the PROXY privilege for that specific user account, and if that privilege is defined WITH GRANT OPTION. For example, the following example fails because the granter does not have the PROXY privilege for that specific user account at all:

SELECT USER(), CURRENT_USER();
+-----------------+-----------------+
| USER()          | CURRENT_USER()  |
+-----------------+-----------------+
| alice@localhost | alice@localhost |
+-----------------+-----------------+

SHOW GRANTS;
+-----------------------------------------------------------------------------------------------------------------------+
| Grants for alice@localhost                                                                                            |
+-----------------------------------------------------------------------------------------------------------------------+
| GRANT ALL PRIVILEGES ON *.* TO 'alice'@'localhost' IDENTIFIED BY PASSWORD '*2470C0C06DEE42FD1618BB99005ADCA2EC9D1E19' |
+-----------------------------------------------------------------------------------------------------------------------+

GRANT PROXY ON 'dba'@'localhost' TO 'bob'@'localhost';
ERROR 1698 (28000): Access denied for user 'alice'@'localhost'

And the following example fails because the granter does have the PROXY privilege for that specific user account, but it is not defined WITH GRANT OPTION:

SELECT USER(), CURRENT_USER();
+-----------------+-----------------+
| USER()          | CURRENT_USER()  |
+-----------------+-----------------+
| alice@localhost | alice@localhost |
+-----------------+-----------------+

SHOW GRANTS;
+-----------------------------------------------------------------------------------------------------------------------+
| Grants for alice@localhost                                                                                            |
+-----------------------------------------------------------------------------------------------------------------------+
| GRANT ALL PRIVILEGES ON *.* TO 'alice'@'localhost' IDENTIFIED BY PASSWORD '*2470C0C06DEE42FD1618BB99005ADCA2EC9D1E19' |
| GRANT PROXY ON 'dba'@'localhost' TO 'alice'@'localhost'                                                               |
+-----------------------------------------------------------------------------------------------------------------------+

GRANT PROXY ON 'dba'@'localhost' TO 'bob'@'localhost';
ERROR 1698 (28000): Access denied for user 'alice'@'localhost'

But the following example succeeds because the granter does have the PROXY privilege for that specific user account, and it is defined WITH GRANT OPTION:

SELECT USER(), CURRENT_USER();
+-----------------+-----------------+
| USER()          | CURRENT_USER()  |
+-----------------+-----------------+
| alice@localhost | alice@localhost |
+-----------------+-----------------+

SHOW GRANTS;
+-----------------------------------------------------------------------------------------------------------------------------------------+
| Grants for alice@localhost                                                                                                              |
+-----------------------------------------------------------------------------------------------------------------------------------------+
| GRANT ALL PRIVILEGES ON *.* TO 'alice'@'localhost' IDENTIFIED BY PASSWORD '*2470C0C06DEE42FD1618BB99005ADCA2EC9D1E19' WITH GRANT OPTION |
| GRANT PROXY ON 'dba'@'localhost' TO 'alice'@'localhost' WITH GRANT OPTION                                                               |
+-----------------------------------------------------------------------------------------------------------------------------------------+

GRANT PROXY ON 'dba'@'localhost' TO 'bob'@'localhost';

A user account can grant the PROXY privilege for any other user account if the granter has the PROXY privilege for the ''@'%' anonymous user account, like this:

GRANT PROXY ON ''@'%' TO 'dba'@'localhost' WITH GRANT OPTION;

For example, the following example succeeds because the user can grant the PROXY privilege for any other user account:

SELECT USER(), CURRENT_USER();
+-----------------+-----------------+
| USER()          | CURRENT_USER()  |
+-----------------+-----------------+
| alice@localhost | alice@localhost |
+-----------------+-----------------+

SHOW GRANTS;
+-----------------------------------------------------------------------------------------------------------------------------------------+
| Grants for alice@localhost                                                                                                              |
+-----------------------------------------------------------------------------------------------------------------------------------------+
| GRANT ALL PRIVILEGES ON *.* TO 'alice'@'localhost' IDENTIFIED BY PASSWORD '*2470C0C06DEE42FD1618BB99005ADCA2EC9D1E19' WITH GRANT OPTION |
| GRANT PROXY ON ''@'%' TO 'alice'@'localhost' WITH GRANT OPTION                                                                          |
+-----------------------------------------------------------------------------------------------------------------------------------------+

GRANT PROXY ON 'app1_dba'@'localhost' TO 'bob'@'localhost';
Query OK, 0 rows affected (0.004 sec)

GRANT PROXY ON 'app2_dba'@'localhost' TO 'carol'@'localhost';
Query OK, 0 rows affected (0.004 sec)

The default root user accounts created by mysql_install_db have this privilege. For example:

GRANT ALL PRIVILEGES ON *.* TO 'root'@'localhost' WITH GRANT OPTION;
GRANT PROXY ON ''@'%' TO 'root'@'localhost' WITH GRANT OPTION;

This allows the default root user accounts to grant the PROXY privilege for any other user account, and it also allows the default root user accounts to grant others the privilege to do the same.

Authentication Options

The authentication options for the GRANT statement are the same as those for the CREATE USER statement.

IDENTIFIED BY 'password'

The optional IDENTIFIED BY clause can be used to provide an account with a password. The password should be specified in plain text. It will be hashed by the PASSWORD function prior to being stored to the mysql.user table.

For example, if our password is mariadb, then we can create the user with:

GRANT USAGE ON *.* TO foo2@test IDENTIFIED BY 'mariadb';

If you do not specify a password with the IDENTIFIED BY clause, the user will be able to connect without a password. A blank password is not a wildcard to match any password. The user must connect without providing a password if no password is set.

If the user account already exists and if you provide the IDENTIFIED BY clause, then the user's password will be changed. You must have the privileges needed for the SET PASSWORD statement to change a user's password with GRANT.

The only authentication plugins that this clause supports are mysql_native_password and mysql_old_password.

IDENTIFIED BY PASSWORD 'password_hash'

The optional IDENTIFIED BY PASSWORD clause can be used to provide an account with a password that has already been hashed. The password should be specified as a hash that was provided by the PASSWORD function. It will be stored to the mysql.user table as-is.

For example, if our password is mariadb, then we can find the hash with:

SELECT PASSWORD('mariadb');
+-------------------------------------------+
| PASSWORD('mariadb')                       |
+-------------------------------------------+
| *54958E764CE10E50764C2EECBB71D01F08549980 |
+-------------------------------------------+
1 row in set (0.00 sec)

And then we can create a user with the hash:

GRANT USAGE ON *.* TO foo2@test IDENTIFIED BY PASSWORD '*54958E764CE10E50764C2EECBB71D01F08549980';

If you do not specify a password with the IDENTIFIED BY clause, the user will be able to connect without a password. A blank password is not a wildcard to match any password. The user must connect without providing a password if no password is set.

If the user account already exists and if you provide the IDENTIFIED BY clause, then the user's password will be changed. You must have the privileges needed for the SET PASSWORD statement to change a user's password with GRANT.

The only authentication plugins that this clause supports are mysql_native_password and mysql_old_password.

IDENTIFIED {VIA|WITH} authentication_plugin

The optional IDENTIFIED VIA authentication_plugin allows you to specify that the account should be authenticated by a specific authentication plugin. The plugin name must be an active authentication plugin as per SHOW PLUGINS. If it doesn't show up in that output, then you will need to install it with INSTALL PLUGIN or INSTALL SONAME.

For example, this could be used with the PAM authentication plugin:

GRANT USAGE ON *.* TO foo2@test IDENTIFIED VIA pam;

Some authentication plugins allow additional arguments to be specified after a USING or AS keyword. For example, the PAM authentication plugin accepts a service name:

GRANT USAGE ON *.* TO foo2@test IDENTIFIED VIA pam USING 'mariadb';

The exact meaning of the additional argument would depend on the specific authentication plugin.

MariaDB starting with 10.4.0

The USING or AS keyword can also be used to provide a plain-text password to a plugin if it's provided as an argument to the PASSWORD() function. This is only valid for authentication plugins that have implemented a hook for the PASSWORD() function. For example, the ed25519 authentication plugin supports this:

CREATE USER safe@'%' IDENTIFIED VIA ed25519 USING PASSWORD('secret');
MariaDB starting with 10.4.3

One can specify many authentication plugins, they all work as alternatives ways of authenticating a user:

CREATE USER safe@'%' IDENTIFIED VIA ed25519 USING PASSWORD('secret') OR unix_socket;

By default, when you create a user without specifying an authentication plugin, MariaDB uses the mysql_native_password plugin.

Resource Limit Options

MariaDB starting with 10.2.0

MariaDB 10.2.0 introduced a number of resource limit options.

It is possible to set per-account limits for certain server resources. The following table shows the values that can be set per account:

Limit TypeDecription
MAX_QUERIES_PER_HOURNumber of statements that the account can issue per hour (including updates)
MAX_UPDATES_PER_HOURNumber of updates (not queries) that the account can issue per hour
MAX_CONNECTIONS_PER_HOURNumber of connections that the account can start per hour
MAX_USER_CONNECTIONSNumber of simultaneous connections that can be accepted from the same account; if it is 0, max_connections will be used instead; if max_connections is 0, there is no limit for this account's simultaneous connections.
MAX_STATEMENT_TIMETimeout, in seconds, for statements executed by the user. See also Aborting Statements that Exceed a Certain Time to Execute.

If any of these limits are set to 0, then there is no limit for that resource for that user.

To set resource limits for an account, if you do not want to change that account's privileges, you can issue a GRANT statement with the USAGE privilege, which has no meaning. The statement can name some or all limit types, in any order.

Here is an example showing how to set resource limits:

GRANT USAGE ON *.* TO 'someone'@'localhost' WITH
    MAX_USER_CONNECTIONS 0
    MAX_QUERIES_PER_HOUR 200;

The resources are tracked per account, which means 'user'@'server'; not per user name or per connection.

The count can be reset for all users using FLUSH USER_RESOURCES, FLUSH PRIVILEGES or mysqladmin reload.

Users with the CONNECTION ADMIN privilege (in MariaDB 10.5.2 and later) or the SUPER privilege are not restricted by max_user_connections, max_connections, or max_password_errors.

Per account resource limits are stored in the user table, in the mysql database. Columns used for resources limits are named max_questions, max_updates, max_connections (for MAX_CONNECTIONS_PER_HOUR), and max_user_connections (for MAX_USER_CONNECTIONS).

TLS Options

By default, MariaDB transmits data between the server and clients without encrypting it. This is generally acceptable when the server and client run on the same host or in networks where security is guaranteed through other means. However, in cases where the server and client exist on separate networks or they are in a high-risk network, the lack of encryption does introduce security concerns as a malicious actor could potentially eavesdrop on the traffic as it is sent over the network between them.

To mitigate this concern, MariaDB allows you to encrypt data in transit between the server and clients using the Transport Layer Security (TLS) protocol. TLS was formerly known as Secure Socket Layer (SSL), but strictly speaking the SSL protocol is a predecessor to TLS and, that version of the protocol is now considered insecure. The documentation still uses the term SSL often and for compatibility reasons TLS-related server system and status variables still use the prefix ssl_, but internally, MariaDB only supports its secure successors.

See Secure Connections Overview for more information about how to determine whether your MariaDB server has TLS support.

You can set certain TLS-related restrictions for specific user accounts. For instance, you might use this with user accounts that require access to sensitive data while sending it across networks that you do not control. These restrictions can be enabled for a user account with the CREATE USER, ALTER USER, or GRANT statements. The following options are available:

OptionDescription
REQUIRE NONETLS is not required for this account, but can still be used.
REQUIRE SSLThe account must use TLS, but no valid X509 certificate is required. This option cannot be combined with other TLS options.
REQUIRE X509The account must use TLS and must have a valid X509 certificate. This option implies REQUIRE SSL. This option cannot be combined with other TLS options.
REQUIRE ISSUER 'issuer'The account must use TLS and must have a valid X509 certificate. Also, the Certificate Authority must be the one specified via the string issuer. This option implies REQUIRE X509. This option can be combined with the SUBJECT, and CIPHER options in any order.
REQUIRE SUBJECT 'subject'The account must use TLS and must have a valid X509 certificate. Also, the certificate's Subject must be the one specified via the string subject. This option implies REQUIRE X509. This option can be combined with the ISSUER, and CIPHER options in any order.
REQUIRE CIPHER 'cipher'The account must use TLS, but no valid X509 certificate is required. Also, the encryption used for the connection must use a specific cipher method specified in the string cipher. This option implies REQUIRE SSL. This option can be combined with the ISSUER, and SUBJECT options in any order.

The REQUIRE keyword must be used only once for all specified options, and the AND keyword can be used to separate individual options, but it is not required.

For example, you can create a user account that requires these TLS options with the following:

GRANT USAGE ON *.* TO 'alice'@'%'
    REQUIRE SUBJECT '/CN=alice/O=My Dom, Inc./C=US/ST=Oregon/L=Portland'
    AND ISSUER '/C=FI/ST=Somewhere/L=City/ O=Some Company/CN=Peter Parker/emailAddress=p.parker@marvel.com'
    AND CIPHER 'SHA-DES-CBC3-EDH-RSA';

If any of these options are set for a specific user account, then any client who tries to connect with that user account will have to be configured to connect with TLS.

See Securing Connections for Client and Server for information on how to enable TLS on the client and server.

Roles

Syntax

GRANT role TO grantee [, grantee ... ]
[ WITH ADMIN OPTION ]

grantee:
    rolename
    username [authentication_option]

The GRANT statement is also used to grant the use a role to one or more users or other roles. In order to be able to grant a role, the grantor doing so must have permission to do so (see WITH ADMIN in the CREATE ROLE article).

Specifying the WITH ADMIN OPTION permits the grantee to in turn grant the role to another.

For example, the following commands show how to grant the same role to a couple different users.

GRANT journalist TO hulda;

GRANT journalist TO berengar WITH ADMIN OPTION;

If a user has been granted a role, they do not automatically obtain all permissions associated with that role. These permissions are only in use when the user activates the role with the SET ROLE statement.

Grant Examples

Granting Root-like Privileges

You can create a user that has privileges similar to the default root accounts by executing the following:

CREATE USER 'alexander'@'localhost';
GRANT ALL PRIVILEGES ON  *.* to 'alexander'@'localhost' WITH GRANT OPTION;

See Also

1.1.1.1.5 RENAME USER

Syntax

RENAME USER old_user TO new_user
    [, old_user TO new_user] ...

Description

The RENAME USER statement renames existing MariaDB accounts. To use it, you must have the global CREATE USER privilege or the UPDATE privilege for the mysql database. Each account is named using the same format as for the CREATE USER statement; for example, 'jeffrey'@'localhost'. If you specify only the user name part of the account name, a host name part of '%' is used.

If any of the old user accounts do not exist or any of the new user accounts already exist, ERROR 1396 (HY000) results. If an error occurs, RENAME USER will still rename the accounts that do not result in an error.

Examples

CREATE USER 'donald', 'mickey';
RENAME USER 'donald' TO 'duck'@'localhost', 'mickey' TO 'mouse'@'localhost';

1.1.1.1.6 REVOKE

Contents

  1. Privileges
    1. Syntax
    2. Description
    3. Examples
  2. Roles
    1. Syntax
    2. Description
    3. Example

Privileges

Syntax

REVOKE 
    priv_type [(column_list)]
      [, priv_type [(column_list)]] ...
    ON [object_type] priv_level
    FROM user [, user] ...

REVOKE ALL PRIVILEGES, GRANT OPTION
    FROM user [, user] ...

Description

The REVOKE statement enables system administrators to revoke privileges (or roles - see section below) from MariaDB accounts. Each account is named using the same format as for the GRANT statement; for example, 'jeffrey'@'localhost'. If you specify only the user name part of the account name, a host name part of '%' is used. For details on the levels at which privileges exist, the allowable priv_type and priv_level values, and the syntax for specifying users and passwords, see GRANT.

To use the first REVOKE syntax, you must have the GRANT OPTION privilege, and you must have the privileges that you are revoking.

To revoke all privileges, use the second syntax, which drops all global, database, table, column, and routine privileges for the named user or users:

REVOKE ALL PRIVILEGES, GRANT OPTION FROM user [, user] ...

To use this REVOKE syntax, you must have the global CREATE USER privilege or the UPDATE privilege for the mysql database. See GRANT.

Examples

REVOKE SUPER ON *.* FROM 'alexander'@'localhost';

Roles

Syntax

REVOKE role  [, role ...]
    FROM grantee [, grantee2 ... ]

REVOKE ADMIN OPTION FOR role FROM grantee [, grantee2]

Description

REVOKE is also used to remove a role from a user or another role that it's previously been assigned to. If a role has previously been set as a default role, REVOKE does not remove the record of the default role from the mysql.user table. If the role is subsequently granted again, it will again be the user's default. Use SET DEFAULT ROLE NONE to explicitly remove this.

Before MariaDB 10.1.13, the REVOKE role statement was not permitted in prepared statements.

Example

REVOKE journalist FROM hulda

1.1.1.1.7 SET PASSWORD

Syntax

SET PASSWORD [FOR user] =
    {
        PASSWORD('some password')
      | OLD_PASSWORD('some password')
      | 'encrypted password'
    }

Contents

  1. Syntax
  2. Description
  3. Authentication Plugin Support
  4. Passwordless User Accounts
  5. Example
  6. See Also

Description

The SET PASSWORD statement assigns a password to an existing MariaDB user account.

If the password is specified using the PASSWORD() or OLD_PASSWORD() function, the literal text of the password should be given. If the password is specified without using either function, the password should be the already-encrypted password value as returned by PASSWORD().

OLD_PASSWORD() should only be used if your MariaDB/MySQL clients are very old (< 4.0.0).

With no FOR clause, this statement sets the password for the current user. Any client that has connected to the server using a non-anonymous account can change the password for that account.

With a FOR clause, this statement sets the password for a specific account on the current server host. Only clients that have the UPDATE privilege for the mysql database can do this. The user value should be given in user_name@host_name format, where user_name and host_name are exactly as they are listed in the User and Host columns of the mysql.user table entry.

The argument to PASSWORD() and the password given to MariaDB clients can be of arbitrary length.

Authentication Plugin Support

MariaDB starting with 10.4

In MariaDB 10.4 and later, SET PASSWORD (with or without PASSWORD()) works for accounts authenticated via any authentication plugin that supports passwords stored in the mysql.global_priv table.

The ed25519, mysql_native_password, and mysql_old_password authentication plugins store passwords in the mysql.global_priv table.

If you run SET PASSWORD on an account that authenticates with one of these authentication plugins that stores passwords in the mysql.global_priv table, then the PASSWORD() function is evaluated by the specific authentication plugin used by the account. The authentication plugin hashes the password with a method that is compatible with that specific authentication plugin.

The unix_socket, named_pipe, gssapi, and pam authentication plugins do not store passwords in the mysql.global_priv table. These authentication plugins rely on other methods to authenticate the user.

If you attempt to run SET PASSWORD on an account that authenticates with one of these authentication plugins that doesn't store a password in the mysql.global_priv table, then MariaDB Server will raise a warning like the following:

SET PASSWORD is ignored for users authenticating via unix_socket plugin

See Authentication from MariaDB 10.4 for an overview of authentication changes in MariaDB 10.4.

MariaDB until 10.3

In MariaDB 10.3 and before, SET PASSWORD (with or without PASSWORD()) only works for accounts authenticated via mysql_native_password or mysql_old_password authentication plugins

Passwordless User Accounts

User accounts do not always require passwords to login.

The unix_socket , named_pipe and gssapi authentication plugins do not require a password to authenticate the user.

The pam authentication plugin may or may not require a password to authenticate the user, depending on the specific configuration.

The mysql_native_password and mysql_old_password authentication plugins require passwords for authentication, but the password can be blank. In that case, no password is required.

If you provide a password while attempting to log into the server as an account that doesn't require a password, then MariaDB server will simply ignore the password.

MariaDB starting with 10.4

In MariaDB 10.4 and later, a user account can be defined to use multiple authentication plugins in a specific order of preference. This specific scenario may be more noticeable in these versions, since an account could be associated with some authentication plugins that require a password, and some that do not.

Example

For example, if you had an entry with User and Host column values of 'bob' and '%.loc.gov', you would write the statement like this:

SET PASSWORD FOR 'bob'@'%.loc.gov' = PASSWORD('newpass');

If you want to delete a password for a user, you would do:

SET PASSWORD FOR 'bob'@localhost = PASSWORD("");

See Also

1.1.1.1.8 CREATE ROLE

Syntax

CREATE [OR REPLACE] ROLE [IF NOT EXISTS] role 
  [WITH ADMIN 
    {CURRENT_USER | CURRENT_ROLE | user | role}]

Contents

  1. Syntax
  2. Description
    1. WITH ADMIN
    2. OR REPLACE
    3. IF NOT EXISTS
  3. Examples
  4. See Also

Description

The CREATE ROLE statement creates one or more MariaDB roles. To use it, you must have the global CREATE USER privilege or the INSERT privilege for the mysql database. For each account, CREATE ROLE creates a new row in the mysql.user table that has no privileges, and with the corresponding is_role field set to Y. It also creates a record in the mysql.roles_mapping table.

If any of the specified roles already exist, ERROR 1396 (HY000) results. If an error occurs, CREATE ROLE will still create the roles that do not result in an error. The maximum length for a role is 128 characters. Role names can be quoted, as explained in the Identifier names page. Only one error is produced for all roles which have not been created:

ERROR 1396 (HY000): Operation CREATE ROLE failed for 'a','b','c'

Failed CREATE or DROP operations, for both users and roles, produce the same error code.

PUBLIC and NONE are reserved, and cannot be used as role names. NONE is used to unset a role and PUBLIC has a special use in other systems, such as Oracle, so is reserved for compatibility purposes.

Before MariaDB 10.1.13, the CREATE ROLE statement was not permitted in prepared statements.

For valid identifiers to use as role names, see Identifier Names.

WITH ADMIN

The optional WITH ADMIN clause determines whether the current user, the current role or another user or role has use of the newly created role. If the clause is omitted, WITH ADMIN CURRENT_USER is treated as the default, which means that the current user will be able to GRANT this role to users.

OR REPLACE

If the optional OR REPLACE clause is used, it acts as a shortcut for:

DROP ROLE IF EXISTS name;
CREATE ROLE name ...;

IF NOT EXISTS

When the IF NOT EXISTS clause is used, MariaDB will return a warning instead of an error if the specified role already exists. Cannot be used together with the OR REPLACE clause.

Examples

CREATE ROLE journalist;

CREATE ROLE developer WITH ADMIN lorinda@localhost;

Granting the role to another user. Only user lorinda@localhost has permission to grant the developer role:

 SELECT USER();
+-------------------+
| USER()            |
+-------------------+
| henning@localhost |
+-------------------+
...
GRANT developer TO ian@localhost;
Access denied for user 'henning'@'localhost'

 SELECT USER();
+-------------------+
| USER()            |
+-------------------+
| lorinda@localhost |
+-------------------+

GRANT m_role TO ian@localhost;

The OR REPLACE and IF NOT EXISTS clauses. The journalist role already exists:

CREATE ROLE journalist;
ERROR 1396 (HY000): Operation CREATE ROLE failed for 'journalist'

CREATE OR REPLACE ROLE journalist;
Query OK, 0 rows affected (0.00 sec)

CREATE ROLE IF NOT EXISTS journalist;
Query OK, 0 rows affected, 1 warning (0.00 sec)

SHOW WARNINGS;
+-------+------+---------------------------------------------------+
| Level | Code | Message                                           |
+-------+------+---------------------------------------------------+
| Note  | 1975 | Can't create role 'journalist'; it already exists |
+-------+------+---------------------------------------------------+

See Also

1.1.1.1.9 DROP ROLE

Syntax

DROP ROLE [IF EXISTS] role_name [,role_name ...]

Contents

  1. Syntax
  2. Description
    1. IF EXISTS
  3. Examples
  4. See Also

Description

The DROP ROLE statement removes one or more MariaDB roles. To use this statement, you must have the global CREATE USER privilege or the DELETE privilege for the mysql database.

DROP ROLE does not disable roles for connections which selected them with SET ROLE. If a role has previously been set as a default role, DROP ROLE does not remove the record of the default role from the mysql.user table. If the role is subsequently recreated and granted, it will again be the user's default. Use SET DEFAULT ROLE NONE to explicitly remove this.

If any of the specified user accounts do not exist, ERROR 1396 (HY000) results. If an error occurs, DROP ROLE will still drop the roles that do not result in an error. Only one error is produced for all roles which have not been dropped:

ERROR 1396 (HY000): Operation DROP ROLE failed for 'a','b','c'

Failed CREATE or DROP operations, for both users and roles, produce the same error code.

Before MariaDB 10.1.13, the DROP ROLE statement was not permitted in prepared statements.

IF EXISTS

If the IF EXISTS clause is used, MariaDB will return a warning instead of an error if the role does not exist.

Examples

DROP ROLE journalist;

The same thing using the optional IF EXISTS clause:

DROP ROLE journalist;
ERROR 1396 (HY000): Operation DROP ROLE failed for 'journalist'

DROP ROLE IF EXISTS journalist;
Query OK, 0 rows affected, 1 warning (0.00 sec)

Note (Code 1975): Can't drop role 'journalist'; it doesn't exist

See Also

1.1.1.1.10 SET ROLE

Syntax

SET ROLE { role | NONE }

Contents

  1. Syntax
  2. Description
  3. Example

Description

The SET ROLE statement enables a role, along with all of its associated permissions, for the current session. To unset a role, use NONE .

If a role that doesn't exist, or to which the user has not been assigned, is specified, an ERROR 1959 (OP000): Invalid role specification error occurs.

An automatic SET ROLE is implicitly performed when a user connects if that user has been assigned a default role. See SET DEFAULT ROLE.

Example

SELECT CURRENT_ROLE;
+--------------+
| CURRENT_ROLE |
+--------------+
| NULL         |
+--------------+

SET ROLE staff;

SELECT CURRENT_ROLE;
+--------------+
| CURRENT_ROLE |
+--------------+
| staff        |
+--------------+

SET ROLE NONE;

SELECT CURRENT_ROLE();
+----------------+
| CURRENT_ROLE() |
+----------------+
| NULL           |
+----------------+

1.1.1.1.11 SET DEFAULT ROLE

Contents

  1. Syntax
  2. Description
  3. Examples

Syntax

SET DEFAULT ROLE { role | NONE } [ FOR user@host ]

Description

The SET DEFAULT ROLE statement sets a default role for a specified (or current) user. A default role is automatically enabled when a user connects (an implicit SET ROLE statement is executed immediately after a connection is established).

To be able to set a role as a default, the role must already have been granted to that user, and one needs the privileges to enable this role (if you cannot do SET ROLE X, you won't be able to do SET DEFAULT ROLE X). To set a default role for another user one needs to have write access to the mysql database.

To remove a user's default role, use SET DEFAULT ROLE NONE [ FOR user@host ]. The record of the default role is not removed if the role is dropped or revoked, so if the role is subsequently re-created or granted, it will again be the user's default role.

The default role is stored in the default_role column in the mysql.user table/view, as well as in the Information Schema APPLICABLE_ROLES table, so these can be viewed to see which role has been assigned to a user as the default.

Examples

Setting a default role for the current user:

SET DEFAULT ROLE journalist;

Removing a default role from the current user:

SET DEFAULT ROLE NONE;

Setting a default role for another user. The role has to have been granted to the user before it can be set as default:

CREATE ROLE journalist;
CREATE USER taniel;

SET DEFAULT ROLE journalist FOR taniel;
ERROR 1959 (OP000): Invalid role specification `journalist`

GRANT journalist TO taniel;
SET DEFAULT ROLE journalist FOR taniel;

Viewing mysql.user:

select * from mysql.user where user='taniel'\G
*************************** 1. row ***************************
                  Host: %
                  User: taniel
...
               is_role: N
          default_role: journalist
...

Removing a default role for another user

SET DEFAULT ROLE NONE FOR taniel;

1.1.1.1.12 SHOW GRANTS

Contents

  1. Syntax
  2. Description
    1. Users
    2. Roles
      1. Example
  3. See Also

Syntax

SHOW GRANTS [FOR user|role]

Description

The SHOW GRANTS statement lists privileges granted to a particular user or role.

Users

The statement lists the GRANT statement or statements that must be issued to duplicate the privileges that are granted to a MariaDB user account. The account is named using the same format as for the GRANT statement; for example, 'jeffrey'@'localhost'. If you specify only the user name part of the account name, a host name part of '%' is used. For additional information about specifying account names, see GRANT.

SHOW GRANTS FOR 'root'@'localhost';
+---------------------------------------------------------------------+
| Grants for root@localhost                                           |
+---------------------------------------------------------------------+
| GRANT ALL PRIVILEGES ON *.* TO 'root'@'localhost' WITH GRANT OPTION |
+---------------------------------------------------------------------+

To list the privileges granted to the account that you are using to connect to the server, you can use any of the following statements:

SHOW GRANTS;
SHOW GRANTS FOR CURRENT_USER;
SHOW GRANTS FOR CURRENT_USER();

If SHOW GRANTS FOR CURRENT_USER (or any of the equivalent syntaxes) is used in DEFINER context (such as within a stored procedure that is defined with SQL SECURITY DEFINER), the grants displayed are those of the definer and not the invoker.

Note that the DELETE HISTORY privilege, introduced in MariaDB 10.3.4, was displayed as DELETE VERSIONING ROWS when running SHOW GRANTS until MariaDB 10.3.15 (MDEV-17655).

Roles

SHOW GRANTS can also be used to view the privileges granted to a role.

Example

SHOW GRANTS FOR journalist;
+------------------------------------------+
| Grants for journalist                    |
+------------------------------------------+
| GRANT USAGE ON *.* TO 'journalist'       |
| GRANT DELETE ON `test`.* TO 'journalist' |
+------------------------------------------+

See Also

1.1.1.1.13 SHOW CREATE USER

MariaDB starting with 10.2.0

SHOW CREATE USER was introduced in MariaDB 10.2.0

Syntax

SHOW CREATE USER user_name

Description

Shows the CREATE USER statement that created the given user. The statement requires the SELECT privilege for the mysql database, except for the current user.

Examples

CREATE USER foo4@test require cipher 'text' 
  issuer 'foo_issuer' subject 'foo_subject';

SHOW CREATE USER foo4@test\G
*************************** 1. row ***************************
CREATE USER 'foo4'@'test' 
  REQUIRE ISSUER 'foo_issuer' 
  SUBJECT 'foo_subject' 
  CIPHER 'text'

User Password Expiry:

CREATE USER 'monty'@'localhost' PASSWORD EXPIRE INTERVAL 120 DAY;

SHOW CREATE USER 'monty'@'localhost';
+------------------------------------------------------------------+
| CREATE USER for monty@localhost                                  |
+------------------------------------------------------------------+
| CREATE USER 'monty'@'localhost' PASSWORD EXPIRE INTERVAL 120 DAY |
+------------------------------------------------------------------+

See Also

1.1.1.2 Administrative SQL Statements

SQL statements for administering MariaDB.

There are 1 related questions.

1.1.1.2.1 Table Statements

Articles about creating, modifying, and maintaining tables in MariaDB.

1.1.1.2.1.1 ALTER

This category is for documentation on the various ALTER statements.

There are 1 related questions.

1.1.1.2.1.1.1 ALTER TABLE

Syntax

ALTER [ONLINE] [IGNORE] TABLE [IF EXISTS] tbl_name
    [WAIT n | NOWAIT]
    alter_specification [, alter_specification] ...


alter_specification:
    table_option ...
  | ADD [COLUMN] [IF NOT EXISTS] col_name column_definition
        [FIRST | AFTER col_name ]
  | ADD [COLUMN] [IF NOT EXISTS] (col_name column_definition,...)
  | ADD {INDEX|KEY} [IF NOT EXISTS] [index_name]
        [index_type] (index_col_name,...) [index_option] ...
  | ADD [CONSTRAINT [symbol]] PRIMARY KEY
        [index_type] (index_col_name,...) [index_option] ...
  | ADD [CONSTRAINT [symbol]]
        UNIQUE [INDEX|KEY] [index_name]
        [index_type] (index_col_name,...) [index_option] ...
  | ADD FULLTEXT [INDEX|KEY] [index_name]
        (index_col_name,...) [index_option] ...
  | ADD SPATIAL [INDEX|KEY] [index_name]
        (index_col_name,...) [index_option] ...
  | ADD [CONSTRAINT [symbol]]
        FOREIGN KEY [IF NOT EXISTS] [index_name] (index_col_name,...)
        reference_definition
  | ADD PERIOD FOR SYSTEM_TIME (start_column_name, end_column_name)
  | ALTER [COLUMN] col_name SET DEFAULT literal | (expression)
  | ALTER [COLUMN] col_name DROP DEFAULT
  | ALTER {INDEX|KEY} index_name [NOT] INVISIBLE
  | CHANGE [COLUMN] [IF EXISTS] old_col_name new_col_name column_definition
        [FIRST|AFTER col_name]
  | MODIFY [COLUMN] [IF EXISTS] col_name column_definition
        [FIRST | AFTER col_name]
  | DROP [COLUMN] [IF EXISTS] col_name [RESTRICT|CASCADE]
  | DROP PRIMARY KEY
  | DROP {INDEX|KEY} [IF EXISTS] index_name
  | DROP FOREIGN KEY [IF EXISTS] fk_symbol
  | DROP CONSTRAINT [IF EXISTS] constraint_name
  | DISABLE KEYS
  | ENABLE KEYS
  | RENAME [TO] new_tbl_name
  | ORDER BY col_name [, col_name] ...
  | RENAME COLUMN old_col_name TO new_col_name
  | RENAME {INDEX|KEY} old_index_name TO new_index_name
  | CONVERT TO CHARACTER SET charset_name [COLLATE collation_name]
  | [DEFAULT] CHARACTER SET [=] charset_name
  | [DEFAULT] COLLATE [=] collation_name
  | DISCARD TABLESPACE
  | IMPORT TABLESPACE
  | ALGORITHM [=] {DEFAULT|INPLACE|COPY|NOCOPY|INSTANT}
  | LOCK [=] {DEFAULT|NONE|SHARED|EXCLUSIVE}
  | FORCE
  | partition_options
  | ADD PARTITION [IF NOT EXISTS] (partition_definition)
  | DROP PARTITION [IF EXISTS] partition_names
  | COALESCE PARTITION number
  | REORGANIZE PARTITION [partition_names INTO (partition_definitions)]
  | ANALYZE PARTITION partition_names
  | CHECK PARTITION partition_names
  | OPTIMIZE PARTITION partition_names
  | REBUILD PARTITION partition_names
  | REPAIR PARTITION partition_names
  | EXCHANGE PARTITION partition_name WITH TABLE tbl_name
  | REMOVE PARTITIONING
  | ADD SYSTEM VERSIONING
  | DROP SYSTEM VERSIONING


index_col_name:
    col_name [(length)] [ASC | DESC]


index_type:
    USING {BTREE | HASH | RTREE}


index_option:
    [ KEY_BLOCK_SIZE [=] value
  | index_type
  | WITH PARSER parser_name
  | COMMENT 'string'
  | CLUSTERING={YES| NO} ]
  [ IGNORED | NOT IGNORED ]


table_options:
    table_option [[,] table_option] ...

Contents

  1. Syntax
  2. Description
  3. Privileges
  4. Online DDL
    1. ALTER ONLINE TABLE
  5. WAIT/NOWAIT
  6. IF EXISTS
  7. Column Definitions
  8. Index Definitions
  9. Character Sets and Collations
  10. Alter Specifications
    1. Table Options
    2. ADD COLUMN
    3. DROP COLUMN
    4. MODIFY COLUMN
    5. CHANGE COLUMN
    6. ALTER COLUMN
    7. RENAME INDEX/KEY
    8. RENAME COLUMN
    9. ADD PRIMARY KEY
    10. DROP PRIMARY KEY
    11. ADD FOREIGN KEY
    12. DROP FOREIGN KEY
    13. ADD INDEX
    14. DROP INDEX
    15. ADD UNIQUE INDEX
    16. DROP UNIQUE INDEX
    17. ADD FULLTEXT INDEX
    18. DROP FULLTEXT INDEX
    19. ADD SPATIAL INDEX
    20. DROP SPATIAL INDEX
    21. ENABLE/ DISABLE KEYS
    22. RENAME TO
    23. ADD CONSTRAINT
    24. DROP CONSTRAINT
    25. ADD SYSTEM VERSIONING
    26. DROP SYSTEM VERSIONING
    27. ADD PERIOD FOR SYSTEM_TIME
    28. FORCE
    29. EXCHANGE PARTITION
    30. DISCARD TABLESPACE
    31. IMPORT TABLESPACE
    32. ALGORITHM
      1. ALGORITHM=DEFAULT
      2. ALGORITHM=COPY
      3. ALGORITHM=INPLACE
      4. ALGORITHM=NOCOPY
      5. ALGORITHM=INSTANT
    33. LOCK
  11. Progress Reporting
  12. Aborting ALTER TABLE Operations
  13. Atomic ALTER TABLE
  14. Replication
  15. Examples
  16. See Also

Description

ALTER TABLE enables you to change the structure of an existing table. For example, you can add or delete columns, create or destroy indexes, change the type of existing columns, or rename columns or the table itself. You can also change the comment for the table and the storage engine of the table.

If another connection is using the table, a metadata lock is active, and this statement will wait until the lock is released. This is also true for non-transactional tables.

When adding a UNIQUE index on a column (or a set of columns) which have duplicated values, an error will be produced and the statement will be stopped. To suppress the error and force the creation of UNIQUE indexes, discarding duplicates, the IGNORE option can be specified. This can be useful if a column (or a set of columns) should be UNIQUE but it contains duplicate values; however, this technique provides no control on which rows are preserved and which are deleted. Also, note that IGNORE is accepted but ignored in ALTER TABLE ... EXCHANGE PARTITION statements.

This statement can also be used to rename a table. For details see RENAME TABLE.

When an index is created, the storage engine may use a configurable buffer in the process. Incrementing the buffer speeds up the index creation. Aria and MyISAM allocate a buffer whose size is defined by aria_sort_buffer_size or myisam_sort_buffer_size, also used for REPAIR TABLE. InnoDB allocates three buffers whose size is defined by innodb_sort_buffer_size.

Privileges

Executing the ALTER TABLE statement generally requires at least the ALTER privilege for the table or the database..

If you are renaming a table, then it also requires the DROP, CREATE and INSERT privileges for the table or the database as well.

Online DDL

Online DDL is supported with the ALGORITHM and LOCK clauses.

See InnoDB Online DDL Overview for more information on online DDL with InnoDB.

ALTER ONLINE TABLE

ALTER ONLINE TABLE also works for partitioned tables.

Online ALTER TABLE is available by executing the following:

ALTER ONLINE TABLE ...;

This statement has the following semantics:

This statement is equivalent to the following:

ALTER TABLE ... LOCK=NONE;

See the LOCK alter specification for more information.

This statement is equivalent to the following:

ALTER TABLE ... ALGORITHM=INPLACE;

See the ALGORITHM alter specification for more information.

WAIT/NOWAIT

MariaDB starting with 10.3.0

Set the lock wait timeout. See WAIT and NOWAIT.

IF EXISTS

The IF EXISTS and IF NOT EXISTS clauses are available for the following:

ADD COLUMN       [IF NOT EXISTS]
ADD INDEX        [IF NOT EXISTS]
ADD FOREIGN KEY  [IF NOT EXISTS]
ADD PARTITION    [IF NOT EXISTS]
CREATE INDEX     [IF NOT EXISTS]


DROP COLUMN      [IF EXISTS]
DROP INDEX       [IF EXISTS]
DROP FOREIGN KEY [IF EXISTS]
DROP PARTITION   [IF EXISTS]
CHANGE COLUMN    [IF EXISTS]
MODIFY COLUMN    [IF EXISTS]
DROP INDEX       [IF EXISTS]

When IF EXISTS and IF NOT EXISTS are used in clauses, queries will not report errors when the condition is triggered for that clause. A warning with the same message text will be issued and the ALTER will move on to the next clause in the statement (or end if finished).

MariaDB starting with 10.5.2

If this is directive is used after ALTER ... TABLE, one will not get an error if the table doesn't exist.

Column Definitions

See CREATE TABLE: Column Definitions for information about column definitions.

Index Definitions

See CREATE TABLE: Index Definitions for information about index definitions.

The CREATE INDEX and DROP INDEX statements can also be used to add or remove an index.

Character Sets and Collations

CONVERT TO CHARACTER SET charset_name [COLLATE collation_name]
[DEFAULT] CHARACTER SET [=] charset_name
[DEFAULT] COLLATE [=] collation_name

See Setting Character Sets and Collations for details on setting the character sets and collations.

Alter Specifications

Table Options

See CREATE TABLE: Table Options for information about table options.

ADD COLUMN

... ADD COLUMN [IF NOT EXISTS]  (col_name column_definition,...)

Adds a column to the table. The syntax is the same as in CREATE TABLE. If you are using IF NOT_EXISTS the column will not be added if it was not there already. This is very useful when doing scripts to modify tables.

The FIRST and AFTER clauses affect the physical order of columns in the datafile. Use FIRST to add a column in the first (leftmost) position, or AFTER followed by a column name to add the new column in any other position. Note that, nowadays, the physical position of a column is usually irrelevant.

See also Instant ADD COLUMN for InnoDB.

DROP COLUMN

... DROP COLUMN [IF EXISTS] col_name [CASCADE|RESTRICT]

Drops the column from the table. If you are using IF EXISTS you will not get an error if the column didn't exist. If the column is part of any index, the column will be dropped from them, except if you add a new column with identical name at the same time. The index will be dropped if all columns from the index were dropped. If the column was used in a view or trigger, you will get an error next time the view or trigger is accessed.

MariaDB starting with 10.2.8

Dropping a column that is part of a multi-column UNIQUE constraint is not permitted. For example:

CREATE TABLE a (
  a int,
  b int,
  primary key (a,b)
);

ALTER TABLE x DROP COLUMN a;
[42000][1072] Key column 'A' doesn't exist in table

The reason is that dropping column a would result in the new constraint that all values in column b be unique. In order to drop the column, an explicit DROP PRIMARY KEY and ADD PRIMARY KEY would be required. Up until MariaDB 10.2.7, the column was dropped and the additional constraint applied, resulting in the following structure:

ALTER TABLE x DROP COLUMN a;
Query OK, 0 rows affected (0.46 sec)

DESC x;
+-------+---------+------+-----+---------+-------+
| Field | Type    | Null | Key | Default | Extra |
+-------+---------+------+-----+---------+-------+
| b     | int(11) | NO   | PRI | NULL    |       |
+-------+---------+------+-----+---------+-------+
MariaDB starting with 10.4.0

MariaDB 10.4.0 supports instant DROP COLUMN. DROP COLUMN of an indexed column would imply DROP INDEX (and in the case of a non-UNIQUE multi-column index, possibly ADD INDEX). These will not be allowed with ALGORITHM=INSTANT, but unlike before, they can be allowed with ALGORITHM=NOCOPY

RESTRICT and CASCADE are allowed to make porting from other database systems easier. In MariaDB, they do nothing.

MODIFY COLUMN

Allows you to modify the type of a column. The column will be at the same place as the original column and all indexes on the column will be kept. Note that when modifying column, you should specify all attributes for the new column.

CREATE TABLE t1 (a INT UNSIGNED AUTO_INCREMENT, PRIMARY KEY((a));
ALTER TABLE t1 MODIFY a BIGINT UNSIGNED AUTO_INCREMENT;

CHANGE COLUMN

Works like MODIFY COLUMN except that you can also change the name of the column. The column will be at the same place as the original column and all index on the column will be kept.

CREATE TABLE t1 (a INT UNSIGNED AUTO_INCREMENT, PRIMARY KEY(a));
ALTER TABLE t1 CHANGE a b BIGINT UNSIGNED AUTO_INCREMENT;

ALTER COLUMN

This lets you change column options.

CREATE TABLE t1 (a INT UNSIGNED AUTO_INCREMENT, b varchar(50), PRIMARY KEY(a));
ALTER TABLE t1 ALTER b SET DEFAULT 'hello';

RENAME INDEX/KEY

MariaDB starting with 10.5.2

From MariaDB 10.5.2, it is possible to rename an index using the RENAME INDEX (or RENAME KEY) syntax, for example:

ALTER TABLE t1 RENAME INDEX i_old TO i_new;

RENAME COLUMN

MariaDB starting with 10.5.2

From MariaDB 10.5.2, it is possible to rename a column using the RENAME COLUMN syntax, for example:

ALTER TABLE t1 RENAME COLUMN c_old TO c_new;

ADD PRIMARY KEY

Add a primary key.

For PRIMARY KEY indexes, you can specify a name for the index, but it is silently ignored, and the name of the index is always PRIMARY.

See Getting Started with Indexes: Primary Key for more information.

DROP PRIMARY KEY

Drop a primary key.

For PRIMARY KEY indexes, you can specify a name for the index, but it is silently ignored, and the name of the index is always PRIMARY.

See Getting Started with Indexes: Primary Key for more information.

ADD FOREIGN KEY

Add a foreign key.

For FOREIGN KEY indexes, a reference definition must be provided.

For FOREIGN KEY indexes, you can specify a name for the constraint, using the CONSTRAINT keyword. That name will be used in error messages.

First, you have to specify the name of the target (parent) table and a column or a column list which must be indexed and whose values must match to the foreign key's values. The MATCH clause is accepted to improve the compatibility with other DBMS's, but has no meaning in MariaDB. The ON DELETE and ON UPDATE clauses specify what must be done when a DELETE (or a REPLACE) statements attempts to delete a referenced row from the parent table, and when an UPDATE statement attempts to modify the referenced foreign key columns in a parent table row, respectively. The following options are allowed:

  • RESTRICT: The delete/update operation is not performed. The statement terminates with a 1451 error (SQLSTATE '2300').
  • NO ACTION: Synonym for RESTRICT.
  • CASCADE: The delete/update operation is performed in both tables.
  • SET NULL: The update or delete goes ahead in the parent table, and the corresponding foreign key fields in the child table are set to NULL. (They must not be defined as NOT NULL for this to succeed).
  • SET DEFAULT: This option is implemented only for the legacy PBXT storage engine, which is disabled by default and no longer maintained. It sets the child table's foreign key fields to their DEFAULT values when the referenced parent table key entries are updated or deleted.

If either clause is omitted, the default behavior for the omitted clause is RESTRICT.

See Foreign Keys for more information.

DROP FOREIGN KEY

Drop a foreign key.

See Foreign Keys for more information.

ADD INDEX

Add a plain index.

Plain indexes are regular indexes that are not unique, and are not acting as a primary key or a foreign key. They are also not the "specialized" FULLTEXT or SPATIAL indexes.

See Getting Started with Indexes: Plain Indexes for more information.

DROP INDEX

Drop a plain index.

Plain indexes are regular indexes that are not unique, and are not acting as a primary key or a foreign key. They are also not the "specialized" FULLTEXT or SPATIAL indexes.

See Getting Started with Indexes: Plain Indexes for more information.

ADD UNIQUE INDEX

Add a unique index.

The UNIQUE keyword means that the index will not accept duplicated values, except for NULLs. An error will raise if you try to insert duplicate values in a UNIQUE index.

For UNIQUE indexes, you can specify a name for the constraint, using the CONSTRAINT keyword. That name will be used in error messages.

See Getting Started with Indexes: Unique Index for more information.

DROP UNIQUE INDEX

Drop a unique index.

The UNIQUE keyword means that the index will not accept duplicated values, except for NULLs. An error will raise if you try to insert duplicate values in a UNIQUE index.

For UNIQUE indexes, you can specify a name for the constraint, using the CONSTRAINT keyword. That name will be used in error messages.

See Getting Started with Indexes: Unique Index for more information.

ADD FULLTEXT INDEX

Add a FULLTEXT index.

See Full-Text Indexes for more information.

DROP FULLTEXT INDEX

Drop a FULLTEXT index.

See Full-Text Indexes for more information.

ADD SPATIAL INDEX

Add a SPATIAL index.

See SPATIAL INDEX for more information.

DROP SPATIAL INDEX

Drop a SPATIAL index.

See SPATIAL INDEX for more information.

ENABLE/ DISABLE KEYS

DISABLE KEYS will disable all non unique keys for the table for storage engines that support this (at least MyISAM and Aria). This can be used to speed up inserts into empty tables.

ENABLE KEYS will enable all disabled keys.

RENAME TO

Renames the table. See also RENAME TABLE.

ADD CONSTRAINT

Modifies the table adding a constraint on a particular column or columns.

MariaDB starting with 10.2.1

MariaDB 10.2.1 introduced new ways to define a constraint.

Note: Before MariaDB 10.2.1, constraint expressions were accepted in syntax, but ignored.

ALTER TABLE table_name 
ADD CONSTRAINT [constraint_name] CHECK(expression);

Before a row is inserted or updated, all constraints are evaluated in the order they are defined. If any constraint fails, then the row will not be updated. One can use most deterministic functions in a constraint, including UDF's.

CREATE TABLE account_ledger (
	id INT PRIMARY KEY AUTO_INCREMENT,
	transaction_name VARCHAR(100),
	credit_account VARCHAR(100),
	credit_amount INT,
	debit_account VARCHAR(100),
	debit_amount INT);

ALTER TABLE account_ledger 
ADD CONSTRAINT is_balanced 
    CHECK((debit_amount + credit_amount) = 0);

The constraint_name is optional. If you don't provide one in the ALTER TABLE statement, MariaDB auto-generates a name for you. This is done so that you can remove it later using DROP CONSTRAINT clause.

You can disable all constraint expression checks by setting the variable check_constraint_checks to OFF. You may find this useful when loading a table that violates some constraints that you want to later find and fix in SQL.

To view constraints on a table, query information_schema.TABLE_CONSTRAINTS:

SELECT CONSTRAINT_NAME, TABLE_NAME, CONSTRAINT_TYPE 
FROM information_schema.TABLE_CONSTRAINTS
WHERE TABLE_NAME = 'account_ledger';

+-----------------+----------------+-----------------+
| CONSTRAINT_NAME | TABLE_NAME     | CONSTRAINT_TYPE |
+-----------------+----------------+-----------------+
| is_balanced     | account_ledger | CHECK           |
+-----------------+----------------+-----------------+

DROP CONSTRAINT

MariaDB starting with 10.2.22

DROP CONSTRAINT for UNIQUE and FOREIGN KEY constraints was introduced in MariaDB 10.2.22 and MariaDB 10.3.13.

MariaDB starting with 10.2.1

DROP CONSTRAINT for CHECK constraints was introduced in MariaDB 10.2.1

Modifies the table, removing the given constraint.

ALTER TABLE table_name
DROP CONSTRAINT constraint_name;

When you add a constraint to a table, whether through a CREATE TABLE or ALTER TABLE...ADD CONSTRAINT statement, you can either set a constraint_name yourself, or allow MariaDB to auto-generate one for you. To view constraints on a table, query information_schema.TABLE_CONSTRAINTS. For instance,

CREATE TABLE t (
   a INT,
   b INT,
   c INT,
   CONSTRAINT CHECK(a > b),
   CONSTRAINT check_equals CHECK(a = c)); 

SELECT CONSTRAINT_NAME, TABLE_NAME, CONSTRAINT_TYPE 
FROM information_schema.TABLE_CONSTRAINTS
WHERE TABLE_NAME = 't';

+-----------------+----------------+-----------------+
| CONSTRAINT_NAME | TABLE_NAME     | CONSTRAINT_TYPE |
+-----------------+----------------+-----------------+
| check_equals    | t              | CHECK           |
| CONSTRAINT_1    | t              | CHECK           |
+-----------------+----------------+-----------------+

To remove a constraint from the table, issue an ALTER TABLE...DROP CONSTRAINT statement. For example,

ALTER TABLE t DROP CONSTRAINT is_unique;

ADD SYSTEM VERSIONING

MariaDB starting with 10.3.4

System-versioned tables was added in MariaDB 10.3.4.

Add system versioning.

DROP SYSTEM VERSIONING

MariaDB starting with 10.3.4

System-versioned tables was added in MariaDB 10.3.4.

Drop system versioning.

ADD PERIOD FOR SYSTEM_TIME

MariaDB starting with 10.3.4

System-versioned tables was added in MariaDB 10.3.4.

FORCE

ALTER TABLE ... FORCE can force MariaDB to re-build the table.

In MariaDB 5.5 and before, this could only be done by setting the ENGINE table option to its old value. For example, for an InnoDB table, one could execute the following:

ALTER TABLE tab_name ENGINE = InnoDB;

The FORCE option can be used instead. For example, :

ALTER TABLE tab_name FORCE;

With InnoDB, the table rebuild will only reclaim unused space (i.e. the space previously used for deleted rows) if the innodb_file_per_table system variable is set to ON. If the system variable is OFF, then the space will not be reclaimed, but it will be-re-used for new data that's later added.

EXCHANGE PARTITION

This is used to exchange the tablespace files between a partition and another table.

See copying InnoDB's transportable tablespaces for more information.

DISCARD TABLESPACE

This is used to discard an InnoDB table's tablespace.

See copying InnoDB's transportable tablespaces for more information.

IMPORT TABLESPACE

This is used to import an InnoDB table's tablespace. The tablespace should have been copied from its original server after executing FLUSH TABLES FOR EXPORT.

See copying InnoDB's transportable tablespaces for more information.

ALTER TABLE ... IMPORT only applies to InnoDB tables. Most other popular storage engines, such as Aria and MyISAM, will recognize their data files as soon as they've been placed in the proper directory under the datadir, and no special DDL is required to import them.

ALGORITHM

The ALTER TABLE statement supports the ALGORITHM clause. This clause is one of the clauses that is used to implement online DDL. ALTER TABLE supports several different algorithms. An algorithm can be explicitly chosen for an ALTER TABLE operation by setting the ALGORITHM clause. The supported values are:

  • ALGORITHM=DEFAULT - This implies the default behavior for the specific statement, such as if no ALGORITHM clause is specified.
  • ALGORITHM=COPY
  • ALGORITHM=INPLACE
  • ALGORITHM=NOCOPY - This was added in MariaDB 10.3.7.
  • ALGORITHM=INSTANT - This was added in MariaDB 10.3.7.

See InnoDB Online DDL Overview: ALGORITHM for information on how the ALGORITHM clause affects InnoDB.

ALGORITHM=DEFAULT

The default behavior, which occurs if ALGORITHM=DEFAULT is specified, or if ALGORITHM is not specified at all, usually only makes a copy if the operation doesn't support being done in-place at all. In this case, the most efficient available algorithm will usually be used.

However, in MariaDB 10.3.6 and before, if the value of the old_alter_table system variable is set to ON, then the default behavior is to perform ALTER TABLE operations by making a copy of the table using the old algorithm.

In MariaDB 10.3.7 and later, the old_alter_table system variable is deprecated. Instead, the alter_algorithm system variable defines the default algorithm for ALTER TABLE operations.

ALGORITHM=COPY

ALGORITHM=COPY is the name for the original ALTER TABLE algorithm from early MariaDB versions.

When ALGORITHM=COPY is set, MariaDB essentially does the following operations:

-- Create a temporary table with the new definition
CREATE TEMPORARY TABLE tmp_tab (
...
);

-- Copy the data from the original table
INSERT INTO tmp_tab
   SELECT * FROM original_tab;

-- Drop the original table
DROP TABLE original_tab;

-- Rename the temporary table, so that it replaces the original one
RENAME TABLE tmp_tab TO original_tab;

This algorithm is very inefficient, but it is generic, so it works for all storage engines.

If ALGORITHM=COPY is specified, then the copy algorithm will be used even if it is not necessary. This can result in a lengthy table copy. If multiple ALTER TABLE operations are required that each require the table to be rebuilt, then it is best to specify all operations in a single ALTER TABLE statement, so that the table is only rebuilt once.

ALGORITHM=INPLACE

ALGORITHM=COPY can be incredibly slow, because the whole table has to be copied and rebuilt. ALGORITHM=INPLACE was introduced as a way to avoid this by performing operations in-place and avoiding the table copy and rebuild, when possible.

When ALGORITHM=INPLACE is set, the underlying storage engine uses optimizations to perform the operation while avoiding the table copy and rebuild. However, INPLACE is a bit of a misnomer, since some operations may still require the table to be rebuilt for some storage engines. Regardless, several operations can be performed without a full copy of the table for some storage engines.

A more accurate name would have been ALGORITHM=ENGINE, where ENGINE refers to an "engine-specific" algorithm.

If an ALTER TABLE operation supports ALGORITHM=INPLACE, then it can be performed using optimizations by the underlying storage engine, but it may rebuilt.

See InnoDB Online DDL Operations with ALGORITHM=INPLACE for more.

ALGORITHM=NOCOPY

ALGORITHM=NOCOPY was introduced in MariaDB 10.3.7.

ALGORITHM=INPLACE can sometimes be surprisingly slow in instances where it has to rebuild the clustered index, because when the clustered index has to be rebuilt, the whole table has to be rebuilt. ALGORITHM=NOCOPY was introduced as a way to avoid this.

If an ALTER TABLE operation supports ALGORITHM=NOCOPY, then it can be performed without rebuilding the clustered index.

If ALGORITHM=NOCOPY is specified for an ALTER TABLE operation that does not support ALGORITHM=NOCOPY, then an error will be raised. In this case, raising an error is preferable, if the alternative is for the operation to rebuild the clustered index, and perform unexpectedly slowly.

See InnoDB Online DDL Operations with ALGORITHM=NOCOPY for more.

ALGORITHM=INSTANT

ALGORITHM=INSTANT was introduced in MariaDB 10.3.7.

ALGORITHM=INPLACE can sometimes be surprisingly slow in instances where it has to modify data files. ALGORITHM=INSTANT was introduced as a way to avoid this.

If an ALTER TABLE operation supports ALGORITHM=INSTANT, then it can be performed without modifying any data files.

If ALGORITHM=INSTANT is specified for an ALTER TABLE operation that does not support ALGORITHM=INSTANT, then an error will be raised. In this case, raising an error is preferable, if the alternative is for the operation to modify data files, and perform unexpectedly slowly.

See InnoDB Online DDL Operations with ALGORITHM=INSTANT for more.

LOCK

The ALTER TABLE statement supports the LOCK clause. This clause is one of the clauses that is used to implement online DDL. ALTER TABLE supports several different locking strategies. A locking strategy can be explicitly chosen for an ALTER TABLE operation by setting the LOCK clause. The supported values are:

  • DEFAULT: Acquire the least restrictive lock on the table that is supported for the specific operation. Permit the maximum amount of concurrency that is supported for the specific operation.
  • NONE: Acquire no lock on the table. Permit all concurrent DML. If this locking strategy is not permitted for an operation, then an error is raised.
  • SHARED: Acquire a read lock on the table. Permit read-only concurrent DML. If this locking strategy is not permitted for an operation, then an error is raised.
  • EXCLUSIVE: Acquire a write lock on the table. Do not permit concurrent DML.

Different storage engines support different locking strategies for different operations. If a specific locking strategy is chosen for an ALTER TABLE operation, and that table's storage engine does not support that locking strategy for that specific operation, then an error will be raised.

If the LOCK clause is not explicitly set, then the operation uses LOCK=DEFAULT.

ALTER ONLINE TABLE is equivalent to LOCK=NONE. Therefore, the ALTER ONLINE TABLE statement can be used to ensure that your ALTER TABLE operation allows all concurrent DML.

See InnoDB Online DDL Overview: LOCK for information on how the LOCK clause affects InnoDB.

Progress Reporting

MariaDB provides progress reporting for ALTER TABLE statement for clients that support the new progress reporting protocol. For example, if you were using the mysql client, then the progress report might look like this::

ALTER TABLE test ENGINE=Aria;
Stage: 1 of 2 'copy to tmp table'    46% of stage

The progress report is also shown in the output of the SHOW PROCESSLIST statement and in the contents of the information_schema.PROCESSLIST table.

See Progress Reporting for more information.

Aborting ALTER TABLE Operations

If an ALTER TABLE operation is being performed and the connection is killed, the changes will be rolled back in a controlled manner. The rollback can be a slow operation as the time it takes is relative to how far the operation has progressed.

MariaDB starting with 10.2.13

Aborting ALTER TABLE ... ALGORITHM=COPY was made faster by removing excessive undo logging (MDEV-11415). This significantly shortens the time it takes to abort a running ALTER TABLE operation.

Atomic ALTER TABLE

MariaDB starting with 10.6.1

From MariaDB 10.6, ALTER TABLE is atomic for most engines, including InnoDB, MyRocks, MyISAM and Aria (MDEV-25180). This means that if there is a crash (server down or power outage) during an ALTER TABLE operation, after recovery, either the old table and associated triggers and status will be intact, or the new table will be active.

In older MariaDB versions one could get leftover #sql-alter..', '#sql-backup..' or 'table_name.frm˝' files if the system crashed during the ALTER TABLE operation.

See Atomic DDL for more information.

Replication

MariaDB starting with 10.8.0

Before MariaDB 10.8.0, ALTER TABLE got fully executed on the primary first, and only then was it replicated and started executing on replicas. From MariaDB 10.8.0, ALTER TABLE gets replicated and starts executing on replicas when it starts executing on the primary, not when it finishes. This way the replication lag caused by a heavy ALTER TABLE can be completely eliminated (MDEV-11675).

Examples

Adding a new column:

ALTER TABLE t1 ADD x INT;

Dropping a column:

ALTER TABLE t1 DROP x;

Modifying the type of a column:

ALTER TABLE t1 MODIFY x bigint unsigned;

Changing the name and type of a column:

ALTER TABLE t1 CHANGE a b bigint unsigned auto_increment;

Combining multiple clauses in a single ALTER TABLE statement, separated by commas:

ALTER TABLE t1 DROP x, ADD x2 INT,  CHANGE y y2 INT;

Changing the storage engine and adding a comment:

ALTER TABLE t1 
  ENGINE = InnoDB 
  COMMENT = 'First of three tables containing usage info';

Rebuilding the table (the previous example will also rebuild the table if it was already InnoDB):

ALTER TABLE t1 FORCE;

Dropping an index:

ALTER TABLE rooms DROP INDEX u;

Adding a unique index:

ALTER TABLE rooms ADD UNIQUE INDEX u(room_number);

From MariaDB 10.5.3, adding a primary key for an application-time period table with a WITHOUT OVERLAPS constraint:

ALTER TABLE rooms ADD PRIMARY KEY(room_number, p WITHOUT OVERLAPS);

See Also

1.1.1.2.1.1.2 ALTER DATABASE

Modifies a database, changing its overall characteristics.

Syntax

ALTER {DATABASE | SCHEMA} [db_name]
    alter_specification ...
ALTER {DATABASE | SCHEMA} db_name
    UPGRADE DATA DIRECTORY NAME

alter_specification:
    [DEFAULT] CHARACTER SET [=] charset_name
  | [DEFAULT] COLLATE [=] collation_name
  | COMMENT [=] 'comment'

Contents

  1. Syntax
  2. Description
    1. COMMENT
  3. Examples
  4. See Also

Description

ALTER DATABASE enables you to change the overall characteristics of a database. These characteristics are stored in the db.opt file in the database directory. To use ALTER DATABASE, you need the ALTER privilege on the database. ALTER SCHEMA is a synonym for ALTER DATABASE.

The CHARACTER SET clause changes the default database character set. The COLLATE clause changes the default database collation. See Character Sets and Collations for more.

You can see what character sets and collations are available using, respectively, the SHOW CHARACTER SET and SHOW COLLATION statements.

Changing the default character set/collation of a database does not change the character set/collation of any stored procedures or stored functions that were previously created, and relied on the defaults. These need to be dropped and recreated in order to apply the character set/collation changes.

The database name can be omitted from the first syntax, in which case the statement applies to the default database.

The syntax that includes the UPGRADE DATA DIRECTORY NAME clause was added in MySQL 5.1.23. It updates the name of the directory associated with the database to use the encoding implemented in MySQL 5.1 for mapping database names to database directory names (see Identifier to File Name Mapping). This clause is for use under these conditions:

  • It is intended when upgrading MySQL to 5.1 or later from older versions.
  • It is intended to update a database directory name to the current encoding format if the name contains special characters that need encoding.
  • The statement is used by mysqlcheck (as invoked by mysql_upgrade).

For example,if a database in MySQL 5.0 has a name of a-b-c, the name contains instance of the `-' character. In 5.0, the database directory is also named a-b-c, which is not necessarily safe for all file systems. In MySQL 5.1 and up, the same database name is encoded as a@002db@002dc to produce a file system-neutral directory name.

When a MySQL installation is upgraded to MySQL 5.1 or later from an older version,the server displays a name such as a-b-c (which is in the old format) as #mysql50#a-b-c, and you must refer to the name using the #mysql50# prefix. Use UPGRADE DATA DIRECTORY NAME in this case to explicitly tell the server to re-encode the database directory name to the current encoding format:

ALTER DATABASE `#mysql50#a-b-c` UPGRADE DATA DIRECTORY NAME;

After executing this statement, you can refer to the database as a-b-c without the special #mysql50# prefix.

COMMENT

MariaDB starting with 10.5.0

From MariaDB 10.5.0, it is possible to add a comment of a maximum of 1024 bytes. If the comment length exceeds this length, a error/warning code 4144 is thrown. The database comment is also added to the db.opt file, as well as to the information_schema.schemata table.

Examples

ALTER DATABASE test CHARACTER SET='utf8'  COLLATE='utf8_bin';

From MariaDB 10.5.0:

ALTER DATABASE p COMMENT='Presentations';

See Also

1.1.1.2.1.1.3 ALTER EVENT

Modifies one or more characteristics of an existing event.

Syntax

ALTER
    [DEFINER = { user | CURRENT_USER }]
    EVENT event_name
    [ON SCHEDULE schedule]
    [ON COMPLETION [NOT] PRESERVE]
    [RENAME TO new_event_name]
    [ENABLE | DISABLE | DISABLE ON SLAVE]
    [COMMENT 'comment']
    [DO sql_statement]

Contents

  1. Syntax
  2. Description
  3. Examples
  4. See Also

Description

The ALTER EVENT statement is used to change one or more of the characteristics of an existing event without the need to drop and recreate it. The syntax for each of the DEFINER, ON SCHEDULE, ON COMPLETION, COMMENT, ENABLE / DISABLE, and DO clauses is exactly the same as when used with CREATE EVENT.

This statement requires the EVENT privilege. When a user executes a successful ALTER EVENT statement, that user becomes the definer for the affected event.

(In MySQL 5.1.11 and earlier, an event could be altered only by its definer, or by a user having the SUPER privilege.)

ALTER EVENT works only with an existing event:

ALTER EVENT no_such_event ON SCHEDULE EVERY '2:3' DAY_HOUR;
ERROR 1539 (HY000): Unknown event 'no_such_event'

Examples

ALTER EVENT myevent 
  ON SCHEDULE AT CURRENT_TIMESTAMP + INTERVAL 2 HOUR 
  DO 
    UPDATE myschema.mytable SET mycol = mycol + 1;

See Also

1.1.1.2.1.1.4 ALTER FUNCTION

Syntax

ALTER FUNCTION func_name [characteristic ...]

characteristic:
    { CONTAINS SQL | NO SQL | READS SQL DATA | MODIFIES SQL DATA }
  | SQL SECURITY { DEFINER | INVOKER }
  | COMMENT 'string'

Contents

  1. Syntax
  2. Description
  3. Example
  4. See Also

Description

This statement can be used to change the characteristics of a stored function. More than one change may be specified in an ALTER FUNCTION statement. However, you cannot change the parameters or body of a stored function using this statement; to make such changes, you must drop and re-create the function using DROP FUNCTION and CREATE FUNCTION.

You must have the ALTER ROUTINE privilege for the function. (That privilege is granted automatically to the function creator.) If binary logging is enabled, the ALTER FUNCTION statement might also require the SUPER privilege, as described in Binary Logging of Stored Routines.

Example

ALTER FUNCTION hello SQL SECURITY INVOKER;

See Also

1.1.1.2.1.1.5 ALTER LOGFILE GROUP

Syntax

ALTER LOGFILE GROUP logfile_group
    ADD UNDOFILE 'file_name'
    [INITIAL_SIZE [=] size]
    [WAIT]
    ENGINE [=] engine_name

The ALTER LOGFILE GROUP statement is not supported by MariaDB. It was originally inherited from MySQL NDB Cluster. See MDEV-19295 for more information.

1.1.1.2.1.1.6 ALTER PROCEDURE

Syntax

ALTER PROCEDURE proc_name [characteristic ...]

characteristic:
    { CONTAINS SQL | NO SQL | READS SQL DATA | MODIFIES SQL DATA }
  | SQL SECURITY { DEFINER | INVOKER }
  | COMMENT 'string'

Description

This statement can be used to change the characteristics of a stored procedure. More than one change may be specified in an ALTER PROCEDURE statement. However, you cannot change the parameters or body of a stored procedure using this statement. To make such changes, you must drop and re-create the procedure using either CREATE OR REPLACE PROCEDURE (since MariaDB 10.1.3) or DROP PROCEDURE and CREATE PROCEDURE (MariaDB 10.1.2 and before).

You must have the ALTER ROUTINE privilege for the procedure. By default, that privilege is granted automatically to the procedure creator. See Stored Routine Privileges.

Example

ALTER PROCEDURE simpleproc SQL SECURITY INVOKER;

See Also

1.1.1.2.1.1.7 ALTER SEQUENCE

1.1.1.2.1.1.8 ALTER SERVER

Syntax

ALTER SERVER server_name
    OPTIONS (option [, option] ...)

Contents

  1. Syntax
  2. Description
  3. Examples
  4. See Also

Description

Alters the server information for server_name, adjusting the specified options as per the CREATE SERVER command. The corresponding fields in the mysql.servers table are updated accordingly. This statement requires the SUPER privilege or, from MariaDB 10.5.2, the FEDERATED ADMIN privilege.

ALTER SERVER is not written to the binary log, irrespective of the binary log format being used. From MariaDB 10.1.13, Galera replicates the CREATE SERVER, ALTER SERVER and DROP SERVER statements.

Examples

ALTER SERVER s OPTIONS (USER 'sally');

See Also

1.1.1.2.1.1.9 ALTER TABLESPACE

The ALTER TABLESPACE statement is not supported by MariaDB. It was originally inherited from MySQL NDB Cluster. In MySQL 5.7 and later, the statement is also supported for InnoDB. However, MariaDB has chosen not to include that specific feature. See MDEV-19294 for more information.

1.1.1.2.1.1.10 ALTER USER

1.1.1.2.1.1.11 ALTER VIEW

Syntax

ALTER
    [ALGORITHM = {UNDEFINED | MERGE | TEMPTABLE}]
    [DEFINER = { user | CURRENT_USER }]
    [SQL SECURITY { DEFINER | INVOKER }]
    VIEW view_name [(column_list)]
    AS select_statement
    [WITH [CASCADED | LOCAL] CHECK OPTION]

Contents

  1. Syntax
  2. Description
  3. Example
  4. See Also

Description

This statement changes the definition of a view, which must exist. The syntax is similar to that for CREATE VIEW and the effect is the same as for CREATE OR REPLACE VIEW if the view exists. This statement requires the CREATE VIEW and DROP privileges for the view, and some privilege for each column referred to in the SELECT statement. ALTER VIEW is allowed only to the definer or users with the SUPER privilege.

Example

ALTER VIEW v AS SELECT a, a*3 AS a2 FROM t;

See Also

1.1.1.2.1.2 ANALYZE TABLE

Syntax

ANALYZE [NO_WRITE_TO_BINLOG | LOCAL] TABLE tbl_name [,tbl_name ...] 
  [PERSISTENT FOR [ALL|COLUMNS ([col_name [,col_name ...]])] 
    [INDEXES ([index_name [,index_name ...]])]]

Contents

  1. Syntax
  2. Description
  3. Engine-Independent Statistics
  4. See Also

Description

ANALYZE TABLE analyzes and stores the key distribution for a table (index statistics). This statement works with MyISAM, Aria and InnoDB tables. During the analysis, InnoDB will allow reads/writes, and MyISAM/Aria reads/inserts. For MyISAM tables, this statement is equivalent to using myisamchk --analyze.

For more information on how the analysis works within InnoDB, see InnoDB Limitations.

MariaDB uses the stored key distribution to decide the order in which tables should be joined when you perform a join on something other than a constant. In addition, key distributions can be used when deciding which indexes to use for a specific table within a query.

This statement requires SELECT and INSERT privileges for the table.

By default, ANALYZE TABLE statements are written to the binary log and will be replicated. The NO_WRITE_TO_BINLOG keyword (LOCAL is an alias) will ensure the statement is not written to the binary log.

From MariaDB 10.3.19, ANALYZE TABLE statements are not logged to the binary log if read_only is set. See also Read-Only Replicas.

ANALYZE TABLE is also supported for partitioned tables. You can use ALTER TABLE ... ANALYZE PARTITION to analyze one or more partitions.

The Aria storage engine supports progress reporting for the ANALYZE TABLE statement.

Engine-Independent Statistics

ANALYZE TABLE supports engine-independent statistics. See Engine-Independent Table Statistics: Collecting Statistics with the ANALYZE TABLE Statement for more information.

See Also

1.1.1.2.1.3 CHECK TABLE

Syntax

CHECK TABLE tbl_name [, tbl_name] ... [option] ...

option = {FOR UPGRADE | QUICK | FAST | MEDIUM | EXTENDED | CHANGED}

Description

CHECK TABLE checks a table or tables for errors. CHECK TABLE works for Archive, Aria, CSV, InnoDB, and MyISAM tables. For Aria and MyISAM tables, the key statistics are updated as well. For CSV, see also Checking and Repairing CSV Tables.

As an alternative, myisamchk is a commandline tool for checking MyISAM tables when the tables are not being accessed.

For checking dynamic columns integrity, COLUMN_CHECK() can be used.

CHECK TABLE can also check views for problems, such as tables that are referenced in the view definition that no longer exist.

CHECK TABLE is also supported for partitioned tables. You can use ALTER TABLE ... CHECK PARTITION to check one or more partitions.

The meaning of the different options are as follows - note that this can vary a bit between storage engines:

FOR UPGRADEDo a very quick check if the storage format for the table has changed so that one needs to do a REPAIR. This is only needed when one upgrades between major versions of MariaDB or MySQL. This is usually done by running mysql_upgrade.
FASTOnly check tables that has not been closed properly or are marked as corrupt. Only supported by the MyISAM and Aria engines. For other engines the table is checked normally
CHANGEDCheck only tables that has changed since last REPAIR / CHECK. Only supported by the MyISAM and Aria engines. For other engines the table is checked normally.
QUICKDo a fast check. For MyISAM and Aria engine this means we skip checking the delete link chain which may take some time.
MEDIUMScan also the data files. Checks integrity between data and index files with checksums. In most cases this should find all possible errors.
EXTENDEDDoes a full check to verify every possible error. For MyISAM and Aria we verify for each row that all it keys exists and points to the row. This may take a long time on big tables!

For most cases running CHECK TABLE without options or MEDIUM should be good enough.

The Aria storage engine supports progress reporting for this statement.

If you want to know if two tables are identical, take a look at CHECKSUM TABLE.

InnoDB

If CHECK TABLE finds an error in an InnoDB table, MariaDB might shutdown to prevent the error propagation. In this case, the problem will be reported in the error log. Otherwise the table or an index might be marked as corrupted, to prevent use. This does not happen with some minor problems, like a wrong number of entries in a secondary index. Those problems are reported in the output of CHECK TABLE.

Each tablespace contains a header with metadata. This header is not checked by this statement.

During the execution of CHECK TABLE, other threads may be blocked.

1.1.1.2.1.4 CHECK VIEW

Syntax

CHECK VIEW view_name

Description

The CHECK VIEW statement was introduced in MariaDB 10.0.18 to assist with fixing MDEV-6916, an issue introduced in MariaDB 5.2 where the view algorithms were swapped. It checks whether the view algorithm is correct. It is run as part of mysql_upgrade, and should not normally be required in regular use.

See Also

1.1.1.2.1.5 CHECKSUM TABLE

Syntax

CHECKSUM TABLE tbl_name [, tbl_name] ... [ QUICK | EXTENDED ]

Contents

  1. Syntax
  2. Description
  3. Differences Between MariaDB and MySQL

Description

CHECKSUM TABLE reports a table checksum. This is very useful if you want to know if two tables are the same (for example on a master and slave).

With QUICK, the live table checksum is reported if it is available, or NULL otherwise. This is very fast. A live checksum is enabled by specifying the CHECKSUM=1 table option when you create the table; currently, this is supported only for Aria and MyISAM tables.

With EXTENDED, the entire table is read row by row and the checksum is calculated. This can be very slow for large tables.

If neither QUICK nor EXTENDED is specified, MariaDB returns a live checksum if the table storage engine supports it and scans the table otherwise.

CHECKSUM TABLE requires the SELECT privilege for the table.

For a nonexistent table, CHECKSUM TABLE returns NULL and generates a warning.

The table row format affects the checksum value. If the row format changes, the checksum will change. This means that when a table created with a MariaDB/MySQL version is upgraded to another version, the checksum value will probably change.

Two identical tables should always match to the same checksum value; however, also for non-identical tables there is a very slight chance that they will return the same value as the hashing algorithm is not completely collision-free.

Differences Between MariaDB and MySQL

CHECKSUM TABLE may give a different result as MariaDB doesn't ignore NULLs in the columns as MySQL 5.1 does (Later MySQL versions should calculate checksums the same way as MariaDB). You can get the 'old style' checksum in MariaDB by starting mysqld with the --old option. Note however that that the MyISAM and Aria storage engines in MariaDB are using the new checksum internally, so if you are using --old, the CHECKSUM command will be slower as it needs to calculate the checksum row by row. Starting from MariaDB Server 10.9, --old is deprecated and will be removed in a future release. Set --old-mode or OLD_MODE to COMPAT_5_1_CHECKSUM to get 'old style' checksum.

1.1.1.2.1.6 CREATE TABLE

Syntax

CREATE [OR REPLACE] [TEMPORARY] TABLE [IF NOT EXISTS] tbl_name
    (create_definition,...) [table_options    ]... [partition_options]
CREATE [OR REPLACE] [TEMPORARY] TABLE [IF NOT EXISTS] tbl_name
    [(create_definition,...)] [table_options   ]... [partition_options]
    select_statement
CREATE [OR REPLACE] [TEMPORARY] TABLE [IF NOT EXISTS] tbl_name
   { LIKE old_table_name | (LIKE old_table_name) }


select_statement:
    [IGNORE | REPLACE] [AS] SELECT ...   (Some legal select statement)

Contents

  1. Syntax
  2. Description
  3. Privileges
  4. CREATE OR REPLACE
    1. Things to be Aware of With CREATE OR REPLACE
  5. CREATE TABLE IF NOT EXISTS
  6. CREATE TEMPORARY TABLE
  7. CREATE TABLE ... LIKE
  8. CREATE TABLE ... SELECT
  9. Column Definitions
    1. NULL and NOT NULL
    2. DEFAULT Column Option
    3. AUTO_INCREMENT Column Option
    4. ZEROFILL Column Option
    5. PRIMARY KEY Column Option
    6. UNIQUE KEY Column Option
    7. COMMENT Column Option
    8. REF_SYSTEM_ID
    9. Generated Columns
    10. COMPRESSED
    11. INVISIBLE
    12. WITH SYSTEM VERSIONING Column Option
    13. WITHOUT SYSTEM VERSIONING Column Option
  10. Index Definitions
    1. Index Categories
      1. Plain Indexes
      2. PRIMARY KEY
      3. UNIQUE
      4. FOREIGN KEY
      5. FULLTEXT
      6. SPATIAL
    2. Index Options
      1. KEY_BLOCK_SIZE Index Option
      2. Index Types
      3. WITH PARSER Index Option
      4. COMMENT Index Option
      5. CLUSTERING Index Option
      6. IGNORED / NOT IGNORED
  11. Periods
  12. Constraint Expressions
  13. Table Options
    1. [STORAGE] ENGINE
    2. AUTO_INCREMENT
    3. AVG_ROW_LENGTH
    4. [DEFAULT] CHARACTER SET/CHARSET
    5. CHECKSUM/TABLE_CHECKSUM
    6. [DEFAULT] COLLATE
    7. COMMENT
    8. CONNECTION
    9. DATA DIRECTORY/INDEX DIRECTORY
    10. DELAY_KEY_WRITE
    11. ENCRYPTED
    12. ENCRYPTION_KEY_ID
    13. IETF_QUOTES
    14. INSERT_METHOD
    15. KEY_BLOCK_SIZE
    16. MIN_ROWS/MAX_ROWS
    17. PACK_KEYS
    18. PAGE_CHECKSUM
    19. PAGE_COMPRESSED
    20. PAGE_COMPRESSION_LEVEL
    21. PASSWORD
    22. RAID_TYPE
    23. ROW_FORMAT
      1. Supported MyISAM Row Formats
      2. Supported Aria Row Formats
      3. Supported InnoDB Row Formats
      4. Other Storage Engines and ROW_FORMAT
    24. SEQUENCE
    25. STATS_AUTO_RECALC
    26. STATS_PERSISTENT
    27. STATS_SAMPLE_PAGES
    28. TRANSACTIONAL
    29. UNION
    30. WITH SYSTEM VERSIONING
  14. Partitions
  15. Sequences
  16. Atomic DDL
  17. Examples
  18. See Also

Description

Use the CREATE TABLE statement to create a table with the given name.

In its most basic form, the CREATE TABLE statement provides a table name followed by a list of columns, indexes, and constraints. By default, the table is created in the default database. Specify a database with db_name.tbl_name. If you quote the table name, you must quote the database name and table name separately as `db_name`.`tbl_name`. This is particularly useful for CREATE TABLE ... SELECT, because it allows to create a table into a database, which contains data from other databases. See Identifier Qualifiers.

If a table with the same name exists, error 1050 results. Use IF NOT EXISTS to suppress this error and issue a note instead. Use SHOW WARNINGS to see notes.

The CREATE TABLE statement automatically commits the current transaction, except when using the TEMPORARY keyword.

For valid identifiers to use as table names, see Identifier Names.

Note: if the default_storage_engine is set to ColumnStore then it needs setting on all UMs. Otherwise when the tables using the default engine are replicated across UMs they will use the wrong engine. You should therefore not use this option as a session variable with ColumnStore.

Microsecond precision can be between 0-6. If no precision is specified it is assumed to be 0, for backward compatibility reasons.

Privileges

Executing the CREATE TABLE statement requires the CREATE privilege for the table or the database.

CREATE OR REPLACE

If the OR REPLACE clause is used and the table already exists, then instead of returning an error, the server will drop the existing table and replace it with the newly defined table.

This syntax was originally added to make replication more robust if it has to rollback and repeat statements such as CREATE ... SELECT on replicas.

CREATE OR REPLACE TABLE table_name (a int);

is basically the same as:

DROP TABLE IF EXISTS table_name;
CREATE TABLE table_name (a int);

with the following exceptions:

  • If table_name was locked with LOCK TABLES it will continue to be locked after the statement.
  • Temporary tables are only dropped if the TEMPORARY keyword was used. (With DROP TABLE, temporary tables are preferred to be dropped before normal tables).

Things to be Aware of With CREATE OR REPLACE

  • The table is dropped first (if it existed), after that the CREATE is done. Because of this, if the CREATE fails, then the table will not exist anymore after the statement. If the table was used with LOCK TABLES it will be unlocked.
  • One can't use OR REPLACE together with IF EXISTS.
  • Slaves in replication will by default use CREATE OR REPLACE when replicating CREATE statements that don''t use IF EXISTS. This can be changed by setting the variable slave-ddl-exec-mode to STRICT.

CREATE TABLE IF NOT EXISTS

If the IF NOT EXISTS clause is used, then the table will only be created if a table with the same name does not already exist. If the table already exists, then a warning will be triggered by default.

CREATE TEMPORARY TABLE

Use the TEMPORARY keyword to create a temporary table that is only available to the current session. Temporary tables are dropped when the session ends. Temporary table names are specific to the session. They will not conflict with other temporary tables from other sessions even if they share the same name. They will shadow names of non-temporary tables or views, if they are identical. A temporary table can have the same name as a non-temporary table which is located in the same database. In that case, their name will reference the temporary table when used in SQL statements. You must have the CREATE TEMPORARY TABLES privilege on the database to create temporary tables. If no storage engine is specified, the default_tmp_storage_engine setting will determine the engine.

ROCKSDB temporary tables cannot be created by setting the default_tmp_storage_engine system variable, or using CREATE TEMPORARY TABLE LIKE. Before MariaDB 10.7, they could be specified, but would silently fail, and a MyISAM table would be created instead. From MariaDB 10.7 an error is returned. Explicitly creating a temporary table with ENGINE=ROCKSDB has never been permitted.

CREATE TABLE ... LIKE

Use the LIKE clause instead of a full table definition to create a table with the same definition as another table, including columns, indexes, and table options. Foreign key definitions, as well as any DATA DIRECTORY or INDEX DIRECTORY table options specified on the original table, will not be created.

CREATE TABLE ... SELECT

You can create a table containing data from other tables using the CREATE ... SELECT statement. Columns will be created in the table for each field returned by the SELECT query.

You can also define some columns normally and add other columns from a SELECT. You can also create columns in the normal way and assign them some values using the query, this is done to force a certain type or other field characteristics. The columns that are not named in the query will be placed before the others. For example:

CREATE TABLE test (a INT NOT NULL, b CHAR(10)) ENGINE=MyISAM
    SELECT 5 AS b, c, d FROM another_table;

Remember that the query just returns data. If you want to use the same indexes, or the same columns attributes ([NOT] NULL, DEFAULT, AUTO_INCREMENT) in the new table, you need to specify them manually. Types and sizes are not automatically preserved if no data returned by the SELECT requires the full size, and VARCHAR could be converted into CHAR. The CAST() function can be used to forcee the new table to use certain types.

Aliases (AS) are taken into account, and they should always be used when you SELECT an expression (function, arithmetical operation, etc).

If an error occurs during the query, the table will not be created at all.

If the new table has a primary key or UNIQUE indexes, you can use the IGNORE or REPLACE keywords to handle duplicate key errors during the query. IGNORE means that the newer values must not be inserted an identical value exists in the index. REPLACE means that older values must be overwritten.

If the columns in the new table are more than the rows returned by the query, the columns populated by the query will be placed after other columns. Note that if the strict SQL_MODE is on, and the columns that are not names in the query do not have a DEFAULT value, an error will raise and no rows will be copied.

Concurrent inserts are not used during the execution of a CREATE ... SELECT.

If the table already exists, an error similar to the following will be returned:

ERROR 1050 (42S01): Table 't' already exists

If the IF NOT EXISTS clause is used and the table exists, a note will be produced instead of an error.

To insert rows from a query into an existing table, INSERT ... SELECT can be used.

Column Definitions

create_definition:
  { col_name column_definition | index_definition | period_definition | CHECK (expr) }


column_definition:
  data_type
    [NOT NULL | NULL] [DEFAULT default_value | (expression)]
    [ON UPDATE [NOW | CURRENT_TIMESTAMP] [(precision)]]
    [AUTO_INCREMENT] [ZEROFILL] [UNIQUE [KEY] | [PRIMARY] KEY]
    [INVISIBLE] [{WITH|WITHOUT} SYSTEM VERSIONING]
    [COMMENT 'string'] [REF_SYSTEM_ID = value]
    [reference_definition]
  | data_type [GENERATED ALWAYS] 
  AS { { ROW {START|END} } | { (expression) [VIRTUAL | PERSISTENT | STORED] } }
      [UNIQUE [KEY]] [COMMENT 'string']


constraint_definition:
   CONSTRAINT [constraint_name] CHECK (expression)

Note: Until MariaDB 10.4, MariaDB accepts the shortcut format with a REFERENCES clause only in ALTER TABLE and CREATE TABLE statements, but that syntax does nothing. For example:

CREATE TABLE b(for_key INT REFERENCES a(not_key));

MariaDB simply parses it without returning any error or warning, for compatibility with other DBMS's. Before MariaDB 10.2.1 this was also true for CHECK constraints. However, only the syntax described below creates foreign keys.

From MariaDB 10.5, MariaDB will attempt to apply the constraint. See Foreign Keys examples.

Each definition either creates a column in the table or specifies and index or constraint on one or more columns. See Indexes below for details on creating indexes.

Create a column by specifying a column name and a data type, optionally followed by column options. See Data Types for a full list of data types allowed in MariaDB.

NULL and NOT NULL

Use the NULL or NOT NULL options to specify that values in the column may or may not be NULL, respectively. By default, values may be NULL. See also NULL Values in MariaDB.

DEFAULT Column Option

MariaDB starting with 10.2.1

The DEFAULT clause was enhanced in MariaDB 10.2.1. Some enhancements include

  • BLOB and TEXT columns now support DEFAULT.
  • The DEFAULT clause can now be used with an expression or function.

Specify a default value using the DEFAULT clause. If you don't specify DEFAULT then the following rules apply:

  • If the column is not defined with NOT NULL, AUTO_INCREMENT or TIMESTAMP, an explicit DEFAULT NULL will be added. Note that in MySQL and in MariaDB before 10.1.6, you may get an explicit DEFAULT for primary key parts, if not specified with NOT NULL.

The default value will be used if you INSERT a row without specifying a value for that column, or if you specify DEFAULT for that column. Before MariaDB 10.2.1 you couldn't usually provide an expression or function to evaluate at insertion time. You had to provide a constant default value instead. The one exception is that you may use CURRENT_TIMESTAMP as the default value for a TIMESTAMP column to use the current timestamp at insertion time.

CURRENT_TIMESTAMP may also be used as the default value for a DATETIME

From MariaDB 10.2.1 you can use most functions in DEFAULT. Expressions should have parentheses around them. If you use a non deterministic function in DEFAULT then all inserts to the table will be replicated in row mode. You can even refer to earlier columns in the DEFAULT expression (excluding AUTO_INCREMENT columns):

CREATE TABLE t1 (a int DEFAULT (1+1), b int DEFAULT (a+1));
CREATE TABLE t2 (a bigint primary key DEFAULT UUID_SHORT());

The DEFAULT clause cannot contain any stored functions or subqueries, and a column used in the clause must already have been defined earlier in the statement.

Since MariaDB 10.2.1, it is possible to assign BLOB or TEXT columns a DEFAULT value. In earlier versions, assigning a default to these columns was not possible.

MariaDB starting with 10.3.3

Starting from 10.3.3 you can also use DEFAULT (NEXT VALUE FOR sequence)

AUTO_INCREMENT Column Option

Use AUTO_INCREMENT to create a column whose value can can be set automatically from a simple counter. You can only use AUTO_INCREMENT on a column with an integer type. The column must be a key, and there can only be one AUTO_INCREMENT column in a table. If you insert a row without specifying a value for that column (or if you specify 0, NULL, or DEFAULT as the value), the actual value will be taken from the counter, with each insertion incrementing the counter by one. You can still insert a value explicitly. If you insert a value that is greater than the current counter value, the counter is set based on the new value. An AUTO_INCREMENT column is implicitly NOT NULL. Use LAST_INSERT_ID to get the AUTO_INCREMENT value most recently used by an INSERT statement.

ZEROFILL Column Option

If the ZEROFILL column option is specified for a column using a numeric data type, then the column will be set to UNSIGNED and the spaces used by default to pad the field are replaced with zeros. ZEROFILL is ignored in expressions or as part of a UNION. ZEROFILL is a non-standard MySQL and MariaDB enhancement.

PRIMARY KEY Column Option

Use PRIMARY KEY to make a column a primary key. A primary key is a special type of a unique key. There can be at most one primary key per table, and it is implicitly NOT NULL.

Specifying a column as a unique key creates a unique index on that column. See the Index Definitions section below for more information.

UNIQUE KEY Column Option

Use UNIQUE KEY (or just UNIQUE) to specify that all values in the column must be distinct from each other. Unless the column is NOT NULL, there may be multiple rows with NULL in the column.

Specifying a column as a unique key creates a unique index on that column. See the Index Definitions section below for more information.

COMMENT Column Option

You can provide a comment for each column using the COMMENT clause. The maximum length is 1024 characters. Use the SHOW FULL COLUMNS statement to see column comments.

REF_SYSTEM_ID

REF_SYSTEM_ID can be used to specify Spatial Reference System IDs for spatial data type columns.

Generated Columns

A generated column is a column in a table that cannot explicitly be set to a specific value in a DML query. Instead, its value is automatically generated based on an expression. This expression might generate the value based on the values of other columns in the table, or it might generate the value by calling built-in functions or user-defined functions (UDFs).

There are two types of generated columns:

  • PERSISTENT or STORED: This type's value is actually stored in the table.
  • VIRTUAL: This type's value is not stored at all. Instead, the value is generated dynamically when the table is queried. This type is the default.

Generated columns are also sometimes called computed columns or virtual columns.

For a complete description about generated columns and their limitations, see Generated (Virtual and Persistent/Stored) Columns.

COMPRESSED

MariaDB starting with 10.3.3

Certain columns may be compressed. See Storage-Engine Independent Column Compression.

INVISIBLE

MariaDB starting with 10.3.3

Columns may be made invisible, and hidden in certain contexts. See Invisible Columns.

WITH SYSTEM VERSIONING Column Option

MariaDB starting with 10.3.4

Columns may be explicitly marked as included from system versioning. See System-versioned tables for details.

WITHOUT SYSTEM VERSIONING Column Option

MariaDB starting with 10.3.4

Columns may be explicitly marked as excluded from system versioning. See System-versioned tables for details.

Index Definitions

index_definition:
    {INDEX|KEY} [index_name] [index_type] (index_col_name,...) [index_option] ...
  | {FULLTEXT|SPATIAL} [INDEX|KEY] [index_name] (index_col_name,...) [index_option] ...
  | [CONSTRAINT [symbol]] PRIMARY KEY [index_type] (index_col_name,...) [index_option] ...
  | [CONSTRAINT [symbol]] UNIQUE [INDEX|KEY] [index_name] [index_type] (index_col_name,...) [index_option] ...
  | [CONSTRAINT [symbol]] FOREIGN KEY [index_name] (index_col_name,...) reference_definition


index_col_name:
    col_name [(length)] [ASC | DESC]


index_type:
    USING {BTREE | HASH | RTREE}


index_option:
    [ KEY_BLOCK_SIZE [=] value
  | index_type
  | WITH PARSER parser_name
  | COMMENT 'string'
  | CLUSTERING={YES| NO} ]
  [ IGNORED | NOT IGNORED ]


reference_definition:
    REFERENCES tbl_name (index_col_name,...)
      [MATCH FULL | MATCH PARTIAL | MATCH SIMPLE]
      [ON DELETE reference_option]
      [ON UPDATE reference_option]


reference_option:
    RESTRICT | CASCADE | SET NULL | NO ACTION

INDEX and KEY are synonyms.

Index names are optional, if not specified an automatic name will be assigned. Index name are needed to drop indexes and appear in error messages when a constraint is violated.

Index Categories

Plain Indexes

Plain indexes are regular indexes that are not unique, and are not acting as a primary key or a foreign key. They are also not the "specialized" FULLTEXT or SPATIAL indexes.

See Getting Started with Indexes: Plain Indexes for more information.

PRIMARY KEY

For PRIMARY KEY indexes, you can specify a name for the index, but it is ignored, and the name of the index is always PRIMARY. From MariaDB 10.3.18 and MariaDB 10.4.8, a warning is explicitly issued if a name is specified. Before then, the name was silently ignored.

See Getting Started with Indexes: Primary Key for more information.

UNIQUE

The UNIQUE keyword means that the index will not accept duplicated values, except for NULLs. An error will raise if you try to insert duplicate values in a UNIQUE index.

For UNIQUE indexes, you can specify a name for the constraint, using the CONSTRAINT keyword. That name will be used in error messages.

See Getting Started with Indexes: Unique Index for more information.

FOREIGN KEY

For FOREIGN KEY indexes, a reference definition must be provided.

For FOREIGN KEY indexes, you can specify a name for the constraint, using the CONSTRAINT keyword. That name will be used in error messages.

First, you have to specify the name of the target (parent) table and a column or a column list which must be indexed and whose values must match to the foreign key's values. The MATCH clause is accepted to improve the compatibility with other DBMS's, but has no meaning in MariaDB. The ON DELETE and ON UPDATE clauses specify what must be done when a DELETE (or a REPLACE) statements attempts to delete a referenced row from the parent table, and when an UPDATE statement attempts to modify the referenced foreign key columns in a parent table row, respectively. The following options are allowed:

  • RESTRICT: The delete/update operation is not performed. The statement terminates with a 1451 error (SQLSTATE '2300').
  • NO ACTION: Synonym for RESTRICT.
  • CASCADE: The delete/update operation is performed in both tables.
  • SET NULL: The update or delete goes ahead in the parent table, and the corresponding foreign key fields in the child table are set to NULL. (They must not be defined as NOT NULL for this to succeed).
  • SET DEFAULT: This option is currently implemented only for the PBXT storage engine, which is disabled by default and no longer maintained. It sets the child table's foreign key fields to their DEFAULT values when the referenced parent table key entries are updated or deleted.

If either clause is omitted, the default behavior for the omitted clause is RESTRICT.

See Foreign Keys for more information.

FULLTEXT

Use the FULLTEXT keyword to create full-text indexes.

See Full-Text Indexes for more information.

SPATIAL

Use the SPATIAL keyword to create geometric indexes.

See SPATIAL INDEX for more information.

Index Options

KEY_BLOCK_SIZE Index Option

The KEY_BLOCK_SIZE index option is similar to the KEY_BLOCK_SIZE table option.

With the InnoDB storage engine, if you specify a non-zero value for the KEY_BLOCK_SIZE table option for the whole table, then the table will implicitly be created with the ROW_FORMAT table option set to COMPRESSED. However, this does not happen if you just set the KEY_BLOCK_SIZE index option for one or more indexes in the table. The InnoDB storage engine ignores the KEY_BLOCK_SIZE index option. However, the SHOW CREATE TABLE statement may still report it for the index.

For information about the KEY_BLOCK_SIZE index option, see the KEY_BLOCK_SIZE table option below.

Index Types

Each storage engine supports some or all index types. See Storage Engine Index Types for details on permitted index types for each storage engine.

Different index types are optimized for different kind of operations:

  • BTREE is the default type, and normally is the best choice. It is supported by all storage engines. It can be used to compare a column's value with a value using the =, >, >=, <, <=, BETWEEN, and LIKE operators. BTREE can also be used to find NULL values. Searches against an index prefix are possible.
  • HASH is only supported by the MEMORY storage engine. HASH indexes can only be used for =, <=, and >= comparisons. It can not be used for the ORDER BY clause. Searches against an index prefix are not possible.
  • RTREE is the default for SPATIAL indexes, but if the storage engine does not support it BTREE can be used.

Index columns names are listed between parenthesis. After each column, a prefix length can be specified. If no length is specified, the whole column will be indexed. ASC and DESC can be specified for compatibility with are DBMS's, but have no meaning in MariaDB.

WITH PARSER Index Option

The WITH PARSER index option only applies to FULLTEXT indexes and contains the fulltext parser name. The fulltext parser must be an installed plugin.

COMMENT Index Option

A comment of up to 1024 characters is permitted with the COMMENT index option.

The COMMENT index option allows you to specify a comment with user-readable text describing what the index is for. This information is not used by the server itself.

CLUSTERING Index Option

The CLUSTERING index option is only valid for tables using the Tokudb storage engine.

IGNORED / NOT IGNORED

MariaDB starting with 10.6.0

From MariaDB 10.6.0, indexes can be specified to be ignored by the optimizer. See Ignored Indexes.

Periods

MariaDB starting with 10.3.4
period_definition:
    PERIOD FOR SYSTEM_TIME (start_column_name, end_column_name)

MariaDB supports a subset of the standard syntax for periods. At the moment it's only used for creating System-versioned tables. Both columns must be created, must be either of a TIMESTAMP(6) or BIGINT UNSIGNED type, and be generated as ROW START and ROW END accordingly. See System-versioned tables for details.

The table must also have the WITH SYSTEM VERSIONING clause.

Constraint Expressions

MariaDB starting with 10.2.1

MariaDB 10.2.1 introduced new ways to define a constraint.

Note: Before MariaDB 10.2.1, constraint expressions were accepted in the syntax but ignored.

MariaDB 10.2.1 introduced two ways to define a constraint:

  • CHECK(expression) given as part of a column definition.
  • CONSTRAINT [constraint_name] CHECK (expression)

Before a row is inserted or updated, all constraints are evaluated in the order they are defined. If any constraints fails, then the row will not be updated. One can use most deterministic functions in a constraint, including UDFs.

create table t1 (a int check(a>0) ,b int check (b> 0), constraint abc check (a>b));

If you use the second format and you don't give a name to the constraint, then the constraint will get a auto generated name. This is done so that you can later delete the constraint with ALTER TABLE DROP constraint_name.

One can disable all constraint expression checks by setting the variable check_constraint_checks to OFF. This is useful for example when loading a table that violates some constraints that you want to later find and fix in SQL.

See CONSTRAINT for more information.

Table Options

For each individual table you create (or alter), you can set some table options. The general syntax for setting options is:

<OPTION_NAME> = <option_value>, [<OPTION_NAME> = <option_value> ...]

The equal sign is optional.

Some options are supported by the server and can be used for all tables, no matter what storage engine they use; other options can be specified for all storage engines, but have a meaning only for some engines. Also, engines can extend CREATE TABLE with new options.

If the IGNORE_BAD_TABLE_OPTIONS SQL_MODE is enabled, wrong table options generate a warning; otherwise, they generate an error.

table_option:    
    [STORAGE] ENGINE [=] engine_name
  | AUTO_INCREMENT [=] value
  | AVG_ROW_LENGTH [=] value
  | [DEFAULT] CHARACTER SET [=] charset_name
  | CHECKSUM [=] {0 | 1}
  | [DEFAULT] COLLATE [=] collation_name
  | COMMENT [=] 'string'
  | CONNECTION [=] 'connect_string'
  | DATA DIRECTORY [=] 'absolute path to directory'
  | DELAY_KEY_WRITE [=] {0 | 1}
  | ENCRYPTED [=] {YES | NO}
  | ENCRYPTION_KEY_ID [=] value
  | IETF_QUOTES [=] {YES | NO}
  | INDEX DIRECTORY [=] 'absolute path to directory'
  | INSERT_METHOD [=] { NO | FIRST | LAST }
  | KEY_BLOCK_SIZE [=] value
  | MAX_ROWS [=] value
  | MIN_ROWS [=] value
  | PACK_KEYS [=] {0 | 1 | DEFAULT}
  | PAGE_CHECKSUM [=] {0 | 1}
  | PAGE_COMPRESSED [=] {0 | 1}
  | PAGE_COMPRESSION_LEVEL [=] {0 .. 9}
  | PASSWORD [=] 'string'
  | ROW_FORMAT [=] {DEFAULT|DYNAMIC|FIXED|COMPRESSED|REDUNDANT|COMPACT|PAGE}
  | SEQUENCE [=] {0|1}
  | STATS_AUTO_RECALC [=] {DEFAULT|0|1}
  | STATS_PERSISTENT [=] {DEFAULT|0|1}
  | STATS_SAMPLE_PAGES [=] {DEFAULT|value}
  | TABLESPACE tablespace_name
  | TRANSACTIONAL [=]  {0 | 1}
  | UNION [=] (tbl_name[,tbl_name]...)
  | WITH SYSTEM VERSIONING

[STORAGE] ENGINE

[STORAGE] ENGINE specifies a storage engine for the table. If this option is not used, the default storage engine is used instead. That is, the default_storage_engine session option value if it is set, or the value specified for the --default-storage-engine mysqld startup option, or the default storage engine, InnoDB. If the specified storage engine is not installed and active, the default value will be used, unless the NO_ENGINE_SUBSTITUTION SQL MODE is set (default). This is only true for CREATE TABLE, not for ALTER TABLE. For a list of storage engines that are present in your server, issue a SHOW ENGINES.

AUTO_INCREMENT

AUTO_INCREMENT specifies the initial value for the AUTO_INCREMENT primary key. This works for MyISAM, Aria, InnoDB/XtraDB, MEMORY, and ARCHIVE tables. You can change this option with ALTER TABLE, but in that case the new value must be higher than the highest value which is present in the AUTO_INCREMENT column. If the storage engine does not support this option, you can insert (and then delete) a row having the wanted value - 1 in the AUTO_INCREMENT column.

AVG_ROW_LENGTH

AVG_ROW_LENGTH is the average rows size. It only applies to tables using MyISAM and Aria storage engines that have the ROW_FORMAT table option set to FIXED format.

MyISAM uses MAX_ROWS and AVG_ROW_LENGTH to decide the maximum size of a table (default: 256TB, or the maximum file size allowed by the system).

[DEFAULT] CHARACTER SET/CHARSET

[DEFAULT] CHARACTER SET (or [DEFAULT] CHARSET) is used to set a default character set for the table. This is the character set used for all columns where an explicit character set is not specified. If this option is omitted or DEFAULT is specified, database's default character set will be used. See Setting Character Sets and Collations for details on setting the character sets.

CHECKSUM/TABLE_CHECKSUM

CHECKSUM (or TABLE_CHECKSUM) can be set to 1 to maintain a live checksum for all table's rows. This makes write operations slower, but CHECKSUM TABLE will be very fast. This option is only supported for MyISAM and Aria tables.

[DEFAULT] COLLATE

[DEFAULT] COLLATE is used to set a default collation for the table. This is the collation used for all columns where an explicit character set is not specified. If this option is omitted or DEFAULT is specified, database's default option will be used. See Setting Character Sets and Collations for details on setting the collations

COMMENT

COMMENT is a comment for the table. The maximum length is 2048 characters. Also used to define table parameters when creating a Spider table.

CONNECTION

CONNECTION is used to specify a server name or a connection string for a Spider, CONNECT, Federated or FederatedX table.

DATA DIRECTORY/INDEX DIRECTORY

DATA DIRECTORY and INDEX DIRECTORY are supported for MyISAM and Aria, and DATA DIRECTORY is also supported by InnoDB if the innodb_file_per_table server system variable is enabled, but only in CREATE TABLE, not in ALTER TABLE. So, carefully choose a path for InnoDB tables at creation time, because it cannot be changed without dropping and re-creating the table. These options specify the paths for data files and index files, respectively. If these options are omitted, the database's directory will be used to store data files and index files. Note that these table options do not work for partitioned tables (use the partition options instead), or if the server has been invoked with the --skip-symbolic-links startup option. To avoid the overwriting of old files with the same name that could be present in the directories, you can use the --keep_files_on_create option (an error will be issued if files already exist). These options are ignored if the NO_DIR_IN_CREATE SQL_MODE is enabled (useful for replication slaves). Also note that symbolic links cannot be used for InnoDB tables.

DATA DIRECTORY works by creating symlinks from where the table would normally have been (inside the datadir) to where the option specifies. For security reasons, to avoid bypassing the privilege system, the server does not permit symlinks inside the datadir. Therefore, DATA DIRECTORY cannot be used to specify a location inside the datadir. An attempt to do so will result in an error 1210 (HY000) Incorrect arguments to DATA DIRECTORY.

DELAY_KEY_WRITE

DELAY_KEY_WRITE is supported by MyISAM and Aria, and can be set to 1 to speed up write operations. In that case, when data are modified, the indexes are not updated until the table is closed. Writing the changes to the index file altogether can be much faster. However, note that this option is applied only if the delay_key_write server variable is set to 'ON'. If it is 'OFF' the delayed index writes are always disabled, and if it is 'ALL' the delayed index writes are always used, disregarding the value of DELAY_KEY_WRITE.

ENCRYPTED

The ENCRYPTED table option can be used to manually set the encryption status of an InnoDB table. See InnoDB Encryption for more information.

Aria does not support the ENCRYPTED table option. See MDEV-18049.

See Data-at-Rest Encryption for more information.

ENCRYPTION_KEY_ID

The ENCRYPTION_KEY_ID table option can be used to manually set the encryption key of an InnoDB table. See InnoDB Encryption for more information.

Aria does not support the ENCRYPTION_KEY_ID table option. See MDEV-18049.

See Data-at-Rest Encryption for more information.

IETF_QUOTES

For the CSV storage engine, the IETF_QUOTES option, when set to YES, enables IETF-compatible parsing of embedded quote and comma characters. Enabling this option for a table improves compatibility with other tools that use CSV, but is not compatible with MySQL CSV tables, or MariaDB CSV tables created without this option. Disabled by default.

INSERT_METHOD

INSERT_METHOD is only used with MERGE tables. This option determines in which underlying table the new rows should be inserted. If you set it to 'NO' (which is the default) no new rows can be added to the table (but you will still be able to perform INSERTs directly against the underlying tables). FIRST means that the rows are inserted into the first table, and LAST means that thet are inserted into the last table.

KEY_BLOCK_SIZE

KEY_BLOCK_SIZE is used to determine the size of key blocks, in bytes or kilobytes. However, this value is just a hint, and the storage engine could modify or ignore it. If KEY_BLOCK_SIZE is set to 0, the storage engine's default value will be used.

With the InnoDB storage engine, if you specify a non-zero value for the KEY_BLOCK_SIZE table option for the whole table, then the table will implicitly be created with the ROW_FORMAT table option set to COMPRESSED.

MIN_ROWS/MAX_ROWS

MIN_ROWS and MAX_ROWS let the storage engine know how many rows you are planning to store as a minimum and as a maximum. These values will not be used as real limits, but they help the storage engine to optimize the table. MIN_ROWS is only used by MEMORY storage engine to decide the minimum memory that is always allocated. MAX_ROWS is used to decide the minimum size for indexes.

PACK_KEYS

PACK_KEYS can be used to determine whether the indexes will be compressed. Set it to 1 to compress all keys. With a value of 0, compression will not be used. With the DEFAULT value, only long strings will be compressed. Uncompressed keys are faster.

PAGE_CHECKSUM

PAGE_CHECKSUM is only applicable to Aria tables, and determines whether indexes and data should use page checksums for extra safety.

PAGE_COMPRESSED

PAGE_COMPRESSED is used to enable InnoDB page compression for InnoDB tables.

PAGE_COMPRESSION_LEVEL

PAGE_COMPRESSION_LEVEL is used to set the compression level for InnoDB page compression for InnoDB tables. The table must also have the PAGE_COMPRESSED table option set to 1.

Valid values for PAGE_COMPRESSION_LEVEL are 1 (the best speed) through 9 (the best compression), .

PASSWORD

PASSWORD is unused.

RAID_TYPE

RAID_TYPE is an obsolete option, as the raid support has been disabled since MySQL 5.0.

ROW_FORMAT

The ROW_FORMAT table option specifies the row format for the data file. Possible values are engine-dependent.

Supported MyISAM Row Formats

For MyISAM, the supported row formats are:

  • FIXED
  • DYNAMIC
  • COMPRESSED

The COMPRESSED row format can only be set by the myisampack command line tool.

See MyISAM Storage Formats for more information.

Supported Aria Row Formats

For Aria, the supported row formats are:

  • PAGE
  • FIXED
  • DYNAMIC.

See Aria Storage Formats for more information.

Supported InnoDB Row Formats

For InnoDB, the supported row formats are:

  • COMPACT
  • REDUNDANT
  • COMPRESSED
  • DYNAMIC.

If the ROW_FORMAT table option is set to FIXED for an InnoDB table, then the server will either return an error or a warning depending on the value of the innodb_strict_mode system variable. If the innodb_strict_mode system variable is set to OFF, then a warning is issued, and MariaDB will create the table using the default row format for the specific MariaDB server version. If the innodb_strict_mode system variable is set to ON, then an error will be raised.

See InnoDB Storage Formats for more information.

Other Storage Engines and ROW_FORMAT

Other storage engines do not support the ROW_FORMAT table option.

SEQUENCE

MariaDB starting with 10.3

If the table is a sequence, then it will have the SEQUENCE set to 1.

STATS_AUTO_RECALC

STATS_AUTO_RECALC indicates whether to automatically recalculate persistent statistics (see STATS_PERSISTENT, below) for an InnoDB table. If set to 1, statistics will be recalculated when more than 10% of the data has changed. When set to 0, stats will be recalculated only when an ANALYZE TABLE is run. If set to DEFAULT, or left out, the value set by the innodb_stats_auto_recalc system variable applies. See InnoDB Persistent Statistics.

STATS_PERSISTENT

STATS_PERSISTENT indicates whether the InnoDB statistics created by ANALYZE TABLE will remain on disk or not. It can be set to 1 (on disk), 0 (not on disk, the pre-MariaDB 10 behavior), or DEFAULT (the same as leaving out the option), in which case the value set by the innodb_stats_persistent system variable will apply. Persistent statistics stored on disk allow the statistics to survive server restarts, and provide better query plan stability. See InnoDB Persistent Statistics.

STATS_SAMPLE_PAGES

STATS_SAMPLE_PAGES indicates how many pages are used to sample index statistics. If 0 or DEFAULT, the default value, the innodb_stats_sample_pages value is used. See InnoDB Persistent Statistics.

TRANSACTIONAL

TRANSACTIONAL is only applicable for Aria tables. In future Aria tables created with this option will be fully transactional, but currently this provides a form of crash protection. See Aria Storage Engine for more details.

UNION

UNION must be specified when you create a MERGE table. This option contains a comma-separated list of MyISAM tables which are accessed by the new table. The list is enclosed between parenthesis. Example: UNION = (t1,t2)

WITH SYSTEM VERSIONING

WITH SYSTEM VERSIONING is used for creating System-versioned tables.

Partitions

partition_options:
    PARTITION BY
        { [LINEAR] HASH(expr)
        | [LINEAR] KEY(column_list)
        | RANGE(expr)
        | LIST(expr)
        | SYSTEM_TIME [INTERVAL time_quantity time_unit] [LIMIT num] }
    [PARTITIONS num]
    [SUBPARTITION BY
        { [LINEAR] HASH(expr)
        | [LINEAR] KEY(column_list) }
      [SUBPARTITIONS num]
    ]
    [(partition_definition [, partition_definition] ...)]


partition_definition:
    PARTITION partition_name
        [VALUES {LESS THAN {(expr) | MAXVALUE} | IN (value_list)}]
        [[STORAGE] ENGINE [=] engine_name]
        [COMMENT [=] 'comment_text' ]
        [DATA DIRECTORY [=] 'data_dir']
        [INDEX DIRECTORY [=] 'index_dir']
        [MAX_ROWS [=] max_number_of_rows]
        [MIN_ROWS [=] min_number_of_rows]
        [TABLESPACE [=] tablespace_name]
        [NODEGROUP [=] node_group_id]
        [(subpartition_definition [, subpartition_definition] ...)]


subpartition_definition:
    SUBPARTITION logical_name
        [[STORAGE] ENGINE [=] engine_name]
        [COMMENT [=] 'comment_text' ]
        [DATA DIRECTORY [=] 'data_dir']
        [INDEX DIRECTORY [=] 'index_dir']
        [MAX_ROWS [=] max_number_of_rows]
        [MIN_ROWS [=] min_number_of_rows]
        [TABLESPACE [=] tablespace_name]
        [NODEGROUP [=] node_group_id]

If the PARTITION BY clause is used, the table will be partitioned. A partition method must be explicitly indicated for partitions and subpartitions. Partition methods are:

  • [LINEAR] HASH creates a hash key which will be used to read and write rows. The partition function can be any valid SQL expression which returns an INTEGER number. Thus, it is possible to use the HASH method on an integer column, or on functions which accept integer columns as an argument. However, VALUES LESS THAN and VALUES IN clauses can not be used with HASH. An example: 
CREATE TABLE t1 (a INT, b CHAR(5), c DATETIME)
    PARTITION BY HASH ( YEAR(c) );

[LINEAR] HASH can be used for subpartitions, too.

  • [LINEAR] KEY is similar to HASH, but the index has an even distribution of data. Also, the expression can only be a column or a list of columns. VALUES LESS THAN and VALUES IN clauses can not be used with KEY.
  • RANGE partitions the rows using on a range of values, using the VALUES LESS THAN operator. VALUES IN is not allowed with RANGE. The partition function can be any valid SQL expression which returns a single value.
  • LIST assigns partitions based on a table's column with a restricted set of possible values. It is similar to RANGE, but VALUES IN must be used for at least 1 columns, and VALUES LESS THAN is disallowed.
  • SYSTEM_TIME partitioning is used for System-versioned tables to store historical data separately from current data.

Only HASH and KEY can be used for subpartitions, and they can be [LINEAR].

It is possible to define up to 1024 partitions and subpartitions.

The number of defined partitions can be optionally specified as PARTITION count. This can be done to avoid specifying all partitions individually. But you can also declare each individual partition and, additionally, specify a PARTITIONS count clause; in the case, the number of PARTITIONs must equal count.

Also see Partitioning Types Overview.

Sequences

MariaDB starting with 10.3

CREATE TABLE can also be used to create a SEQUENCE. See CREATE SEQUENCE and Sequence Overview.

Atomic DDL

MariaDB starting with 10.6.1

MariaDB 10.6.1 supports Atomic DDL. CREATE TABLE is atomic, except for CREATE OR REPLACE, which is only crash safe.

Examples

create table if not exists test (
a bigint auto_increment primary key,
name varchar(128) charset utf8,
key name (name(32))
) engine=InnoDB default charset latin1;

This example shows a couple of things:

  • Usage of IF NOT EXISTS; If the table already existed, it will not be created. There will not be any error for the client, just a warning.
  • How to create a PRIMARY KEY that is automatically generated.
  • How to specify a table-specific character set and another for a column.
  • How to create an index (name) that is only partly indexed (to save space).

The following clauses will work from MariaDB 10.2.1 only.

CREATE TABLE t1(
  a int DEFAULT (1+1),
  b int DEFAULT (a+1),
  expires DATETIME DEFAULT(NOW() + INTERVAL 1 YEAR),
  x BLOB DEFAULT USER()
);

See Also

1.1.1.2.1.7 DELETE

Contents

  1. Syntax
  2. Description
    1. PARTITION
    2. FOR PORTION OF
    3. RETURNING
    4. Same Source and Target Table
    5. DELETE HISTORY
  3. Examples
    1. Deleting from the Same Source and Target
  4. See Also

Syntax

Single-table syntax:

DELETE [LOW_PRIORITY] [QUICK] [IGNORE] 
  FROM tbl_name [PARTITION (partition_list)]
  [FOR PORTION OF period FROM expr1 TO expr2]
  [WHERE where_condition]
  [ORDER BY ...]
  [LIMIT row_count]
  [RETURNING select_expr 
    [, select_expr ...]]

Multiple-table syntax:

DELETE [LOW_PRIORITY] [QUICK] [IGNORE]
    tbl_name[.*] [, tbl_name[.*]] ...
    FROM table_references
    [WHERE where_condition]

Or:

DELETE [LOW_PRIORITY] [QUICK] [IGNORE]
    FROM tbl_name[.*] [, tbl_name[.*]] ...
    USING table_references
    [WHERE where_condition]

Trimming history:

DELETE HISTORY
  FROM tbl_name [PARTITION (partition_list)]
  [BEFORE SYSTEM_TIME [TIMESTAMP|TRANSACTION] expression]

Description

OptionDescription
LOW_PRIORITYWait until all SELECT's are done before starting the statement. Used with storage engines that uses table locking (MyISAM, Aria etc). See HIGH_PRIORITY and LOW_PRIORITY clauses for details.
QUICKSignal the storage engine that it should expect that a lot of rows are deleted. The storage engine engine can do things to speed up the DELETE like ignoring merging of data blocks until all rows are deleted from the block (instead of when a block is half full). This speeds up things at the expanse of lost space in data blocks. At least MyISAM and Aria support this feature.
IGNOREDon't stop the query even if a not-critical error occurs (like data overflow). See How IGNORE works for a full description.

For the single-table syntax, the DELETE statement deletes rows from tbl_name and returns a count of the number of deleted rows. This count can be obtained by calling the ROW_COUNT() function. The WHERE clause, if given, specifies the conditions that identify which rows to delete. With no WHERE clause, all rows are deleted. If the ORDER BY clause is specified, the rows are deleted in the order that is specified. The LIMIT clause places a limit on the number of rows that can be deleted.

For the multiple-table syntax, DELETE deletes from each tbl_name the rows that satisfy the conditions. In this case, ORDER BY and LIMIT> cannot be used. A DELETE can also reference tables which are located in different databases; see Identifier Qualifiers for the syntax.

where_condition is an expression that evaluates to true for each row to be deleted. It is specified as described in SELECT.

Currently, you cannot delete from a table and select from the same table in a subquery.

You need the DELETE privilege on a table to delete rows from it. You need only the SELECT privilege for any columns that are only read, such as those named in the WHERE clause. See GRANT.

As stated, a DELETE statement with no WHERE clause deletes all rows. A faster way to do this, when you do not need to know the number of deleted rows, is to use TRUNCATE TABLE. However, within a transaction or if you have a lock on the table, TRUNCATE TABLE cannot be used whereas DELETE can. See TRUNCATE TABLE, and LOCK.

PARTITION

See Partition Pruning and Selection for details.

FOR PORTION OF

MariaDB starting with 10.4.3

See Application Time Periods - Deletion by Portion.

RETURNING

It is possible to return a resultset of the deleted rows for a single table to the client by using the syntax DELETE ... RETURNING select_expr [, select_expr2 ...]]

Any of SQL expression that can be calculated from a single row fields is allowed. Subqueries are allowed. The AS keyword is allowed, so it is possible to use aliases.

The use of aggregate functions is not allowed. RETURNING cannot be used in multi-table DELETEs.

MariaDB starting with 10.3.1

Same Source and Target Table

Until MariaDB 10.3.1, deleting from a table with the same source and target was not possible. From MariaDB 10.3.1, this is now possible. For example:

DELETE FROM t1 WHERE c1 IN (SELECT b.c1 FROM t1 b WHERE b.c2=0);
MariaDB starting with 10.3.4

DELETE HISTORY

One can use DELETE HISTORY to delete historical information from System-versioned tables.

Examples

How to use the ORDER BY and LIMIT clauses:

DELETE FROM page_hit ORDER BY timestamp LIMIT 1000000;

How to use the RETURNING clause:

DELETE FROM t RETURNING f1;
+------+
| f1   |
+------+
|    5 |
|   50 |
|  500 |
+------+

The following statement joins two tables: one is only used to satisfy a WHERE condition, but no row is deleted from it; rows from the other table are deleted, instead.

DELETE post FROM blog INNER JOIN post WHERE blog.id = post.blog_id;

Deleting from the Same Source and Target

CREATE TABLE t1 (c1 INT, c2 INT);
DELETE FROM t1 WHERE c1 IN (SELECT b.c1 FROM t1 b WHERE b.c2=0);

Until MariaDB 10.3.1, this returned:

ERROR 1093 (HY000): Table 't1' is specified twice, both as a target for 'DELETE' 
  and as a separate source for

From MariaDB 10.3.1:

Query OK, 0 rows affected (0.00 sec)

See Also

1.1.1.2.1.8 DROP TABLE

Syntax

DROP [TEMPORARY] TABLE [IF EXISTS] [/*COMMENT TO SAVE*/]
    tbl_name [, tbl_name] ...
    [WAIT n|NOWAIT]
    [RESTRICT | CASCADE]

Contents

  1. Syntax
  2. Description
    1. WAIT/NOWAIT
  3. DROP TABLE in replication
  4. Dropping an Internal #sql-... Table
  5. Dropping All Tables in a Database
  6. Atomic DROP TABLE
  7. Examples
  8. Notes
  9. See Also

Description

DROP TABLE removes one or more tables. You must have the DROP privilege for each table. All table data and the table definition are removed, as well as triggers associated to the table, so be careful with this statement! If any of the tables named in the argument list do not exist, MariaDB returns an error indicating by name which non-existing tables it was unable to drop, but it also drops all of the tables in the list that do exist.

Important: When a table is dropped, user privileges on the table are not automatically dropped. See GRANT.

If another thread is using the table in an explicit transaction or an autocommit transaction, then the thread acquires a metadata lock (MDL) on the table. The DROP TABLE statement will wait in the "Waiting for table metadata lock" thread state until the MDL is released. MDLs are released in the following cases:

  • If an MDL is acquired in an explicit transaction, then the MDL will be released when the transaction ends.
  • If an MDL is acquired in an autocommit transaction, then the MDL will be released when the statement ends.
  • Transactional and non-transactional tables are handled the same.

Note that for a partitioned table, DROP TABLE permanently removes the table definition, all of its partitions, and all of the data which was stored in those partitions. It also removes the partitioning definition (.par) file associated with the dropped table.

For each referenced table, DROP TABLE drops a temporary table with that name, if it exists. If it does not exist, and the TEMPORARY keyword is not used, it drops a non-temporary table with the same name, if it exists. The TEMPORARY keyword ensures that a non-temporary table will not accidentally be dropped.

Use IF EXISTS to prevent an error from occurring for tables that do not exist. A NOTE is generated for each non-existent table when using IF EXISTS. See SHOW WARNINGS.

If a foreign key references this table, the table cannot be dropped. In this case, it is necessary to drop the foreign key first.

RESTRICT and CASCADE are allowed to make porting from other database systems easier. In MariaDB, they do nothing.

The comment before the table names (/*COMMENT TO SAVE*/) is stored in the binary log. That feature can be used by replication tools to send their internal messages.

It is possible to specify table names as db_name.tab_name. This is useful to delete tables from multiple databases with one statement. See Identifier Qualifiers for details.

The DROP privilege is required to use DROP TABLE on non-temporary tables. For temporary tables, no privilege is required, because such tables are only visible for the current session.

Note: DROP TABLE automatically commits the current active transaction, unless you use the TEMPORARY keyword.

MariaDB starting with 10.5.4

From MariaDB 10.5.4, DROP TABLE reliably deletes table remnants inside a storage engine even if the .frm file is missing. Before then, a missing .frm file would result in the statement failing.

MariaDB starting with 10.3.1

WAIT/NOWAIT

Set the lock wait timeout. See WAIT and NOWAIT.

DROP TABLE in replication

DROP TABLE has the following characteristics in replication:

  • DROP TABLE IF EXISTS are always logged.
  • DROP TABLE without IF EXISTS for tables that don't exist are not written to the binary log.
  • Dropping of TEMPORARY tables are prefixed in the log with TEMPORARY. These drops are only logged when running statement or mixed mode replication.
  • One DROP TABLE statement can be logged with up to 3 different DROP statements:
    • DROP TEMPORARY TABLE list_of_non_transactional_temporary_tables
    • DROP TEMPORARY TABLE list_of_transactional_temporary_tables
    • DROP TABLE list_of_normal_tables

DROP TABLE on the primary is treated on the replica as DROP TABLE IF EXISTS. You can change that by setting slave-ddl-exec-mode to STRICT.

Dropping an Internal #sql-... Table

From MariaDB 10.6, DROP TABLE is atomic and the following does not apply. Until MariaDB 10.5, if the mariadbd/mysqld process is killed during an ALTER TABLE you may find a table named #sql-... in your data directory. In MariaDB 10.3, InnoDB tables with this prefix will be deleted automatically during startup. From MariaDB 10.4, these temporary tables will always be deleted automatically.

If you want to delete one of these tables explicitly you can do so by using the following syntax:

DROP TABLE `#mysql50##sql-...`;

When running an ALTER TABLE…ALGORITHM=INPLACE that rebuilds the table, InnoDB will create an internal #sql-ib table. Until MariaDB 10.3.2, for these tables, the .frm file will be called something else. In order to drop such a table after a server crash, you must rename the #sql*.frm file to match the #sql-ib*.ibd file.

From MariaDB 10.3.3, the same name as the .frm file is used for the intermediate copy of the table. The #sql-ib names are used by TRUNCATE and delayed DROP.

From MariaDB 10.2.19 and MariaDB 10.3.10, the #sql-ib tables will be deleted automatically.

Dropping All Tables in a Database

The best way to drop all tables in a database is by executing DROP DATABASE, which will drop the database itself, and all tables in it.

However, if you want to drop all tables in the database, but you also want to keep the database itself and any other non-table objects in it, then you would need to execute DROP TABLE to drop each individual table. You can construct these DROP TABLE commands by querying the TABLES table in the information_schema database. For example:

SELECT CONCAT('DROP TABLE IF EXISTS `', TABLE_SCHEMA, '`.`', TABLE_NAME, '`;')
FROM information_schema.TABLES
WHERE TABLE_SCHEMA = 'mydb';

Atomic DROP TABLE

MariaDB starting with 10.6.1

From MariaDB 10.6, DROP TABLE for a single table is atomic (MDEV-25180) for most engines, including InnoDB, MyRocks, MyISAM and Aria.

This means that if there is a crash (server down or power outage) during DROP TABLE, all tables that have been processed so far will be completely dropped, including related trigger files and status entries, and the binary log will include a DROP TABLE statement for the dropped tables. Tables for which the drop had not started will be left intact.

In older MariaDB versions, there was a small chance that, during a server crash happening in the middle of DROP TABLE, some storage engines that were using multiple storage files, like MyISAM, could have only a part of its internal files dropped.

In MariaDB 10.5, DROP TABLE was extended to be able to delete a table that was only partly dropped (MDEV-11412) as explained above. Atomic DROP TABLE is the final piece to make DROP TABLE fully reliable.

Dropping multiple tables is crash-safe.

See Atomic DDL for more information.

Examples

DROP TABLE Employees, Customers;

Notes

Beware that DROP TABLE can drop both tables and sequences. This is mainly done to allow old tools like mysqldump to work with sequences.

See Also

1.1.1.2.1.9 Installing System Tables (mysql_install_db)

mysql_install_db initializes the MariaDB data directory and creates the system tables in the mysql database, if they do not exist. MariaDB uses these tables to manage privileges, roles, and plugins. It also uses them to provide the data for the help command in the mysql client.

mysql_install_db works by starting MariaDB Server's mysqld process in --bootstrap mode and sending commands to create the system tables and their content.

There is a version specifically for Windows, mysql_install_db.exe.

To invoke mysql_install_db, use the following syntax:

mysql_install_db --user=mysql

For the options supported by mysql_install_db, see mysql_install_db: Options.

For the option groups read by mysql_install_db, see mysql_install_db: Option Groups.

See mysql_install_db: Installing System Tables for information on the installation process.

See mysql_install_db: Troubleshooting Issues for information on how to troubleshoot the installation process.

See also:

1.1.1.2.1.10 mysqlcheck

MariaDB starting with 10.4.6

From MariaDB 10.4.6, mariadb-check is a symlink to mysqlcheck.

MariaDB starting with 10.5.2

From MariaDB 10.5.2, mariadb-check is the name of the tool, with mysqlcheck a symlink .

Contents

  1. Using mysqlcheck
    1. Options
    2. Option Files
      1. Option Groups
  2. Notes
    1. Default Values
    2. mysqlcheck and auto-repair
    3. mysqlcheck and all-databases
    4. mysqlcheck and verbose

mysqlcheck is a maintenance tool that allows you to check, repair, analyze and optimize multiple tables from the command line.

It is essentially a commandline interface to the CHECK TABLE, REPAIR TABLE, ANALYZE TABLE and OPTIMIZE TABLE commands, and so, unlike myisamchk and aria_chk, requires the server to be running.

This tool does not work with partitioned tables.

Using mysqlcheck

./client/mysqlcheck [OPTIONS] database [tables]

OR

./client/mysqlcheck [OPTIONS] --databases DB1 [DB2 DB3...]

OR

./client/mysqlcheck [OPTIONS] --all-databases

mysqlcheck can be used to CHECK (-c, -m, -C), REPAIR (-r), ANALYZE (-a), or OPTIMIZE (-o) tables. Some of the options (like -e or -q) can be used at the same time. Not all options are supported by all storage engines.

The -c, -r, -a and -o options are exclusive to each other.

The option --check will be used by default, if no other options were specified. You can change the default behavior by making a symbolic link to the binary, or copying it somewhere with another name, the alternatives are:

mysqlrepairThe default option will be -r (--repair)
mysqlanalyzeThe default option will be -a (--analyze)
mysqloptimizeThe default option will be -o (--optimize)

Options

mysqlcheck supports the following options:

OptionDescription
-A, --all-databasesCheck all the databases. This is the same as --databases with all databases selected.
-1, --all-in-1Instead of issuing one query for each table, use one query per database, naming all tables in the database in a comma-separated list.
-a, --analyzeAnalyze given tables.
--auto-repairIf a checked table is corrupted, automatically fix it. Repairing will be done after all tables have been checked.
--character-sets-dir=nameDirectory where character set files are installed.
-c, --checkCheck table for errors.
-C, --check-only-changedCheck only tables that have changed since last check or haven't been closed properly.
-g, --check-upgradeCheck tables for version-dependent changes. May be used with --auto-repair to correct tables requiring version-dependent updates. Automatically enables the --fix-db-names and --fix-table-names options. Used when upgrading
--compressCompress all information sent between the client and server if both support compression.
-B, --databasesCheck several databases. Note that normally mysqlcheck treats the first argument as a database name, and following arguments as table names. With this option, no tables are given, and all name arguments are regarded as database names.
-# , --debug[=name]Output debug log. Often this is 'd:t:o,filename'.
--debug-checkCheck memory and open file usage at exit.
--debug-infoPrint some debug info at exit.
--default-auth=pluginDefault authentication client-side plugin to use.
--default-character-set=nameSet the default character set.
-e, --extendedIf you are using this option with --check, it will ensure that the table is 100 percent consistent, but will take a long time. If you are using this option with --repair, it will force using the old, slow, repair with keycache method, instead of the much faster repair by sorting.
-F, --fastCheck only tables that haven't been closed properly.
--fix-db-namesConvert database names to the format used since MySQL 5.1. Only database names that contain special characters are affected. Used when upgrading from an old MySQL version.
--fix-table-namesConvert table names (including views) to the format used since MySQL 5.1. Only table names that contain special characters are affected. Used when upgrading from an old MySQL version.
--flushFlush each table after check. This is useful if you don't want to have the checked tables take up space in the caches after the check.
-f, --forceContinue even if we get an SQL error.
-?, --helpDisplay this help message and exit.
-h name, --host=nameConnect to the given host.
-m, --medium-checkFaster than extended-check, but only finds 99.99 percent of all errors. Should be good enough for most cases.
-o, --optimizeOptimize tables.
-p, --password[=name]Password to use when connecting to the server. If you use the short option form (-p), you cannot have a space between the option and the password. If you omit the password value following the --password or -p option on the command line, mysqlcheck prompts for one. Specifying a password on the command line should be considered insecure. You can use an option file to avoid giving the password on the command line.
-Z, --persistentWhen using ANALYZE TABLE (--analyze), uses the PERSISTENT FOR ALL option, which forces Engine-independent Statistics for this table to be updated. Added in MariaDB 10.1.10
-W, --pipeOn Windows, connect to the server via a named pipe. This option applies only if the server supports named-pipe connections.
--plugin-dirDirectory for client-side plugins.
-P num, --port=numPort number to use for connection or 0 for default to, in order of preference, my.cnf, $MYSQL_TCP_PORT, /etc/services, built-in default (3306).
--process-tablesPerform the requested operation (check, repair, analyze, optimize) on tables. Enabled by default. Use --skip-process-tables to disable.
--process-views[=val]Perform the requested operation (only CHECK VIEW or REPAIR VIEW). Possible values are NO, YES (correct the checksum, if necessary, add the mariadb-version field), UPGRADE_FROM_MYSQL (same as YES and toggle the algorithm MERGE<->TEMPTABLE.
--protocol=nameThe connection protocol (tcp, socket, pipe, memory) to use for connecting to the server. Useful when other connection parameters would cause a protocol to be used other than the one you want.
-q, --quickIf you are using this option with CHECK TABLE, it prevents the check from scanning the rows to check for wrong links. This is the fastest check. If you are using this option with REPAIR TABLE, it will try to repair only the index tree. This is the fastest repair method for a table.
-r, --repairCan fix almost anything except unique keys that aren't unique.
--shared-memory-base-nameShared-memory name to use for Windows connections using shared memory to a local server (started with the --shared-memory option). Case-sensitive.
-s, --silentPrint only error messages.
--skip-databaseDon't process the database (case-sensitive) specified as argument.
-S name, --socket=nameFor connections to localhost, the Unix socket file to use, or, on Windows, the name of the named pipe to use.
--sslEnables TLS. TLS is also enabled even without setting this option when certain other TLS options are set. Starting with MariaDB 10.2, the --ssl option will not enable verifying the server certificate by default. In order to verify the server certificate, the user must specify the --ssl-verify-server-cert option.
--ssl-ca=nameDefines a path to a PEM file that should contain one or more X509 certificates for trusted Certificate Authorities (CAs) to use for TLS. This option requires that you use the absolute path, not a relative path. See Secure Connections Overview: Certificate Authorities (CAs) for more information. This option implies the --ssl option.
--ssl-capath=nameDefines a path to a directory that contains one or more PEM files that should each contain one X509 certificate for a trusted Certificate Authority (CA) to use for TLS. This option requires that you use the absolute path, not a relative path. The directory specified by this option needs to be run through the openssl rehash command. See Secure Connections Overview: Certificate Authorities (CAs) for more information. This option is only supported if the client was built with OpenSSL or yaSSL. If the client was built with GnuTLS or Schannel, then this option is not supported. See TLS and Cryptography Libraries Used by MariaDB for more information about which libraries are used on which platforms. This option implies the --ssl option.
--ssl-cert=nameDefines a path to the X509 certificate file to use for TLS. This option requires that you use the absolute path, not a relative path. This option implies the --ssl option.
--ssl-cipher=nameList of permitted ciphers or cipher suites to use for TLS. This option implies the --ssl option.
--ssl-crl=nameDefines a path to a PEM file that should contain one or more revoked X509 certificates to use for TLS. This option requires that you use the absolute path, not a relative path. See Secure Connections Overview: Certificate Revocation Lists (CRLs) for more information. This option is only supported if the client was built with OpenSSL or Schannel. If the client was built with yaSSL or GnuTLS, then this option is not supported. See TLS and Cryptography Libraries Used by MariaDB for more information about which libraries are used on which platforms.
--ssl-crlpath=nameDefines a path to a directory that contains one or more PEM files that should each contain one revoked X509 certificate to use for TLS. This option requires that you use the absolute path, not a relative path. The directory specified by this option needs to be run through the openssl rehash command. See Secure Connections Overview: Certificate Revocation Lists (CRLs) for more information. This option is only supported if the client was built with OpenSSL. If the client was built with yaSSL, GnuTLS, or Schannel, then this option is not supported. See TLS and Cryptography Libraries Used by MariaDB for more information about which libraries are used on which platforms.
--ssl-key=nameDefines a path to a private key file to use for TLS. This option requires that you use the absolute path, not a relative path. This option implies the --ssl option.
--ssl-verify-server-certEnables server certificate verification. This option is disabled by default.
--tablesOverrides the --databases or -B option such that all name arguments following the option are regarded as table names.
--use-frmFor repair operations on MyISAM tables, get table structure from .frm file, so the table can be repaired even if the .MYI header is corrupted.
-u, --user=nameUser for login if not current user.
-v, --verbosePrint info about the various stages. You can give this option several times to get even more information. See mysqlcheck and verbose, below.
-V, --versionOutput version information and exit.
--write-binlogWrite ANALYZE, OPTIMIZE and REPAIR TABLE commands to the binary log. Enabled by default; use --skip-write-binlog when commands should not be sent to replication slaves.

Option Files

In addition to reading options from the command-line, mysqlcheck can also read options from option files. If an unknown option is provided to mysqlcheck in an option file, then it is ignored.

The following options relate to how MariaDB command-line tools handles option files. They must be given as the first argument on the command-line:

OptionDescription
--print-defaultsPrint the program argument list and exit.
--no-defaultsDon't read default options from any option file.
--defaults-file=# Only read default options from the given file #.
--defaults-extra-file=# Read this file after the global files are read.
--defaults-group-suffix=# In addition to the default option groups, also read option groups with this suffix.

In MariaDB 10.2 and later, mysqlcheck is linked with MariaDB Connector/C. However, MariaDB Connector/C does not yet handle the parsing of option files for this client. That is still performed by the server option file parsing code. See MDEV-19035 for more information.

Option Groups

mysqlcheck reads options from the following option groups from option files:

GroupDescription
[mysqlcheck] Options read by mysqlcheck, which includes both MariaDB Server and MySQL Server.
[mariadb-check]Options read by mysqlcheck. Available starting with MariaDB 10.4.6.
[client] Options read by all MariaDB and MySQL client programs, which includes both MariaDB and MySQL clients. For example, mysqldump.
[client-server]Options read by all MariaDB client programs and the MariaDB Server. This is useful for options like socket and port, which is common between the server and the clients.
[client-mariadb]Options read by all MariaDB client programs.

Notes

Default Values

To see the default values for the options and also to see the arguments you get from configuration files you can do:

./client/mysqlcheck --print-defaults
./client/mysqlcheck --help

mysqlcheck and auto-repair

When running mysqlcheck with --auto-repair (as done by mysql_upgrade), mysqlcheck will first check all tables and then in a separate phase repair those that failed the check.

mysqlcheck and all-databases

mysqlcheck --all-databases will ignore the internal log tables general_log and slow_log as these can't be checked, repaired or optimized.

mysqlcheck and verbose

Using one --verbose option will give you more information about what mysqlcheck is doing.

Using two --verbose options will also give you connection information.

If you use three --verbose options you will also get, on stdout, all ALTER, RENAME, and CHECK commands that mysqlcheck executes.

1.1.1.2.1.11 OPTIMIZE TABLE

Syntax

OPTIMIZE [NO_WRITE_TO_BINLOG | LOCAL] TABLE
    tbl_name [, tbl_name] ...
    [WAIT n | NOWAIT]

Contents

  1. Syntax
  2. Description
    1. WAIT/NOWAIT
    2. Defragmenting
    3. Updating an InnoDB fulltext index
    4. Defragmenting InnoDB tablespaces
  3. See Also

Description

OPTIMIZE TABLE has two main functions. It can either be used to defragment tables, or to update the InnoDB fulltext index.

MariaDB starting with 10.3.0

WAIT/NOWAIT

Set the lock wait timeout. See WAIT and NOWAIT.

Defragmenting

OPTIMIZE TABLE works for InnoDB (before MariaDB 10.1.1, only if the innodb_file_per_table server system variable is set), Aria, MyISAM and ARCHIVE tables, and should be used if you have deleted a large part of a table or if you have made many changes to a table with variable-length rows (tables that have VARCHAR, VARBINARY, BLOB, or TEXT columns). Deleted rows are maintained in a linked list and subsequent INSERT operations reuse old row positions.

This statement requires SELECT and INSERT privileges for the table.

By default, OPTIMIZE TABLE statements are written to the binary log and will be replicated. The NO_WRITE_TO_BINLOG keyword (LOCAL is an alias) will ensure the statement is not written to the binary log.

From MariaDB 10.3.19, OPTIMIZE TABLE statements are not logged to the binary log if read_only is set. See also Read-Only Replicas.

OPTIMIZE TABLE is also supported for partitioned tables. You can use ALTER TABLE ... OPTIMIZE PARTITION to optimize one or more partitions.

You can use OPTIMIZE TABLE to reclaim the unused space and to defragment the data file. With other storage engines, OPTIMIZE TABLE does nothing by default, and returns this message: " The storage engine for the table doesn't support optimize". However, if the server has been started with the --skip-new option, OPTIMIZE TABLE is linked to ALTER TABLE, and recreates the table. This operation frees the unused space and updates index statistics.

The Aria storage engine supports progress reporting for this statement.

If a MyISAM table is fragmented, concurrent inserts will not be performed until an OPTIMIZE TABLE statement is executed on that table, unless the concurrent_insert server system variable is set to ALWAYS.

Updating an InnoDB fulltext index

When rows are added or deleted to an InnoDB fulltext index, the index is not immediately re-organized, as this can be an expensive operation. Change statistics are stored in a separate location . The fulltext index is only fully re-organized when an OPTIMIZE TABLE statement is run.

By default, an OPTIMIZE TABLE will defragment a table. In order to use it to update fulltext index statistics, the innodb_optimize_fulltext_only system variable must be set to 1. This is intended to be a temporary setting, and should be reset to 0 once the fulltext index has been re-organized.

Since fulltext re-organization can take a long time, the innodb_ft_num_word_optimize variable limits the re-organization to a number of words (2000 by default). You can run multiple OPTIMIZE statements to fully re-organize the index.

Defragmenting InnoDB tablespaces

MariaDB 10.1.1 merged the Facebook/Kakao defragmentation patch, allowing one to use OPTIMIZE TABLE to defragment InnoDB tablespaces. For this functionality to be enabled, the innodb_defragment system variable must be enabled. No new tables are created and there is no need to copy data from old tables to new tables. Instead, this feature loads n pages (determined by innodb-defragment-n-pages) and tries to move records so that pages would be full of records and then frees pages that are fully empty after the operation. Note that tablespace files (including ibdata1) will not shrink as the result of defragmentation, but one will get better memory utilization in the InnoDB buffer pool as there are fewer data pages in use.

See Defragmenting InnoDB Tablespaces for more details.

See Also

1.1.1.2.1.12 RENAME TABLE

Syntax

RENAME TABLE[S] [IF EXISTS] tbl_name 
  [WAIT n | NOWAIT]
  TO new_tbl_name
    [, tbl_name2 TO new_tbl_name2] ...

Contents

  1. Syntax
  2. Description
    1. IF EXISTS
    2. WAIT/NOWAIT
    3. Privileges
    4. Atomic RENAME TABLE

Description

This statement renames one or more tables or views, but not the privileges associated with them.

IF EXISTS

MariaDB starting with 10.5.2

If this directive is used, one will not get an error if the table to be renamed doesn't exist.

The rename operation is done atomically, which means that no other session can access any of the tables while the rename is running. For example, if you have an existing table old_table, you can create another table new_table that has the same structure but is empty, and then replace the existing table with the empty one as follows (assuming that backup_table does not already exist):

CREATE TABLE new_table (...);
RENAME TABLE old_table TO backup_table, new_table TO old_table;

tbl_name can optionally be specified as db_name.tbl_name. See Identifier Qualifiers. This allows to use RENAME to move a table from a database to another (as long as they are on the same filesystem):

RENAME TABLE db1.t TO db2.t;

Note that moving a table to another database is not possible if it has some triggers. Trying to do so produces the following error:

ERROR 1435 (HY000): Trigger in wrong schema

Also, views cannot be moved to another database:

ERROR 1450 (HY000): Changing schema from 'old_db' to 'new_db' is not allowed.

Multiple tables can be renamed in a single statement. The presence or absence of the optional S (RENAME TABLE or RENAME TABLES) has no impact, whether a single or multiple tables are being renamed.

If a RENAME TABLE renames more than one table and one renaming fails, all renames executed by the same statement are rolled back.

Renames are always executed in the specified order. Knowing this, it is also possible to swap two tables' names:

RENAME TABLE t1 TO tmp_table,
    t2 TO t1,
    tmp_table TO t2;

WAIT/NOWAIT

MariaDB starting with 10.3.0

Set the lock wait timeout. See WAIT and NOWAIT.

Privileges

Executing the RENAME TABLE statement requires the DROP, CREATE and INSERT privileges for the table or the database.

Atomic RENAME TABLE

MariaDB starting with 10.6.1

From MariaDB 10.6, RENAME TABLE is atomic for most engines, including InnoDB, MyRocks, MyISAM and Aria (MDEV-23842). This means that if there is a crash (server down or power outage) during RENAME TABLE, all tables will revert to their original names and any changes to trigger files will be reverted.

In older MariaDB version there was a small chance that, during a server crash happening in the middle of RENAME TABLE, some tables could have been renamed (in the worst case partly) while others would not be renamed.

See Atomic DDL for more information.

1.1.1.2.1.13 REPAIR TABLE

Syntax

REPAIR [NO_WRITE_TO_BINLOG | LOCAL] TABLE
    tbl_name [, tbl_name] ...
    [QUICK] [EXTENDED] [USE_FRM]

Description

REPAIR TABLE repairs a possibly corrupted table. By default, it has the same effect as

myisamchk --recover tbl_name

or

aria_chk --recover tbl_name

See aria_chk and myisamchk for more.

REPAIR TABLE works for Archive, Aria, CSV and MyISAM tables. For InnoDB, see recovery modes. For CSV, see also Checking and Repairing CSV Tables. For Archive, this statement also improves compression. If the storage engine does not support this statement, a warning is issued.

This statement requires SELECT and INSERT privileges for the table.

By default, REPAIR TABLE statements are written to the binary log and will be replicated. The NO_WRITE_TO_BINLOG keyword (LOCAL is an alias) will ensure the statement is not written to the binary log.

From MariaDB 10.3.19, REPAIR TABLE statements are not logged to the binary log if read_only is set. See also Read-Only Replicas.

When an index is recreated, the storage engine may use a configurable buffer in the process. Incrementing the buffer speeds up the index creation. Aria and MyISAM allocate a buffer whose size is defined by aria_sort_buffer_size or myisam_sort_buffer_size, also used for ALTER TABLE.

REPAIR TABLE is also supported for partitioned tables. However, the USE_FRM option cannot be used with this statement on a partitioned table.

ALTER TABLE ... REPAIR PARTITION can be used to repair one or more partitions.

The Aria storage engine supports progress reporting for this statement.

1.1.1.2.1.14 REPAIR VIEW

Syntax

REPAIR [NO_WRITE_TO_BINLOG | LOCAL] VIEW  view_name[, view_name] ... [FROM MYSQL]

Contents

  1. Syntax
  2. Description
  3. See Also

Description

The REPAIR VIEW statement was introduced to assist with fixing MDEV-6916, an issue introduced in MariaDB 5.2 where the view algorithms were swapped compared to their MySQL on disk representation. It checks whether the view algorithm is correct. It is run as part of mysql_upgrade, and should not normally be required in regular use.

By default it corrects the checksum and if necessary adds the mariadb-version field. If the optional FROM MYSQL clause is used, and no mariadb-version field is present, the MERGE and TEMPTABLE algorithms are toggled.

By default, REPAIR VIEW statements are written to the binary log and will be replicated. The NO_WRITE_TO_BINLOG keyword (LOCAL is an alias) will ensure the statement is not written to the binary log.

See Also

1.1.1.2.1.15 REPLACE

Syntax

REPLACE [LOW_PRIORITY | DELAYED]
 [INTO] tbl_name [PARTITION (partition_list)] [(col,...)]
 {VALUES | VALUE} ({expr | DEFAULT},...),(...),...
[RETURNING select_expr 
      [, select_expr ...]]

Or:

REPLACE [LOW_PRIORITY | DELAYED]
    [INTO] tbl_name [PARTITION (partition_list)]
    SET col={expr | DEFAULT}, ...
[RETURNING select_expr 
      [, select_expr ...]]

Or:

REPLACE [LOW_PRIORITY | DELAYED]
    [INTO] tbl_name [PARTITION (partition_list)] [(col,...)]
    SELECT ...
[RETURNING select_expr 
      [, select_expr ...]]

Contents

  1. Syntax
  2. Description
    1. PARTITION
    2. REPLACE RETURNING
      1. Examples
  3. Examples
  4. See Also

Description

REPLACE works exactly like INSERT, except that if an old row in the table has the same value as a new row for a PRIMARY KEY or a UNIQUE index, the old row is deleted before the new row is inserted. If the table has more than one UNIQUE keys, it is possible that the new row conflicts with more than one row. In this case, all conflicting rows will be deleted.

The table name can be specified in the form db_name.tbl_name or, if a default database is selected, in the form tbl_name (see Identifier Qualifiers). This allows to use REPLACE ... SELECT to copy rows between different databases.

MariaDB starting with 10.5.0

The RETURNING clause was introduced in MariaDB 10.5.0

Basically it works like this:

BEGIN;
SELECT 1 FROM t1 WHERE key=# FOR UPDATE;
IF found-row
  DELETE FROM t1 WHERE key=# ;
ENDIF
INSERT INTO t1 VALUES (...);
END;

The above can be replaced with:

REPLACE INTO t1 VALUES (...)

REPLACE is a MariaDB/MySQL extension to the SQL standard. It either inserts, or deletes and inserts. For other MariaDB/MySQL extensions to standard SQL --- that also handle duplicate values --- see IGNORE and INSERT ON DUPLICATE KEY UPDATE.

Note that unless the table has a PRIMARY KEY or UNIQUE index, using a REPLACE statement makes no sense. It becomes equivalent to INSERT, because there is no index to be used to determine whether a new row duplicates another.

Values for all columns are taken from the values sSee Partition Pruning and Selection for details.pecified in the REPLACE statement. Any missing columns are set to their default values, just as happens for INSERT. You cannot refer to values from the current row and use them in the new row. If you use an assignment such as 'SET col = col + 1', the reference to the column name on the right hand side is treated as DEFAULT(col), so the assignment is equivalent to 'SET col = DEFAULT(col) + 1'.

To use REPLACE, you must have both the INSERT and DELETE privileges for the table.

There are some gotchas you should be aware of, before using REPLACE:

  • If there is an AUTO_INCREMENT field, a new value will be generated.
  • If there are foreign keys, ON DELETE action will be activated by REPLACE.
  • Triggers on DELETE and INSERT will be activated by REPLACE.

To avoid some of these behaviors, you can use INSERT ... ON DUPLICATE KEY UPDATE.

This statement activates INSERT and DELETE triggers. See Trigger Overview for details.

PARTITION

See Partition Pruning and Selection for details.

REPLACE RETURNING

REPLACE ... RETURNING returns a resultset of the replaced rows.

This returns the listed columns for all the rows that are replaced, or alternatively, the specified SELECT expression. Any SQL expressions which can be calculated can be used in the select expression for the RETURNING clause, including virtual columns and aliases, expressions which use various operators such as bitwise, logical and arithmetic operators, string functions, date-time functions, numeric functions, control flow functions, secondary functions and stored functions. Along with this, statements which have subqueries and prepared statements can also be used.

Examples

Simple REPLACE statement

REPLACE INTO t2 VALUES (1,'Leopard'),(2,'Dog') RETURNING id2, id2+id2 
as Total ,id2|id2, id2&&id2;
+-----+-------+---------+----------+
| id2 | Total | id2|id2 | id2&&id2 |
+-----+-------+---------+----------+
|   1 |     2 |       1 |        1 |
|   2 |     4 |       2 |        1 |
+-----+-------+---------+----------+

Using stored functions in RETURNING

DELIMITER |
CREATE FUNCTION f(arg INT) RETURNS INT
    BEGIN
      RETURN (SELECT arg+arg);
    END|

DELIMITER ;
PREPARE stmt FROM "REPLACE INTO t2 SET id2=3, animal2='Fox' RETURNING f2(id2),
UPPER(animal2)";

EXECUTE stmt;
+---------+----------------+
| f2(id2) | UPPER(animal2) |
+---------+----------------+
|       6 | FOX            |
+---------+----------------+

Subqueries in the statement

REPLACE INTO t1 SELECT * FROM t2 RETURNING (SELECT id2 FROM t2 WHERE 
id2 IN (SELECT id2 FROM t2 WHERE id2=1)) AS new_id;
+--------+
| new_id |
+--------+
|      1 |
|      1 |
|      1 |
|      1 |
+--------+

Subqueries in the RETURNING clause that return more than one row or column cannot be used..

Aggregate functions cannot be used in the RETURNING clause. Since aggregate functions work on a set of values and if the purpose is to get the row count, ROW_COUNT() with SELECT can be used, or it can be used in REPLACE...SEL== Description

REPLACE ... RETURNING returns a resultset of the replaced rows.

This returns the listed columns for all the rows that are replaced, or alternatively, the specified SELECT expression. Any SQL expressions which can be calculated can be used in the select expression for the RETURNING clause, including virtual columns and aliases, expressions which use various operators such as bitwise, logical and arithmetic operators, string functions, date-time functions, numeric functions, control flow functions, secondary functions and stored functions. Along with this, statements which have subqueries and prepared statements can also be used.

Examples

Simple REPLACE statement

REPLACE INTO t2 VALUES (1,'Leopard'),(2,'Dog') RETURNING id2, id2+id2 
as Total ,id2|id2, id2&&id2;
+-----+-------+---------+----------+
| id2 | Total | id2|id2 | id2&&id2 |
+-----+-------+---------+----------+
|   1 |     2 |       1 |        1 |
|   2 |     4 |       2 |        1 |
+-----+-------+---------+----------+

Using stored functions in RETURNING

DELIMITER |
CREATE FUNCTION f(arg INT) RETURNS INT
    BEGIN
      RETURN (SELECT arg+arg);
    END|

DELIMITER ;
PREPARE stmt FROM "REPLACE INTO t2 SET id2=3, animal2='Fox' RETURNING f2(id2),
UPPER(animal2)";

EXECUTE stmt;
+---------+----------------+
| f2(id2) | UPPER(animal2) |
+---------+----------------+
|       6 | FOX            |
+---------+----------------+

Subqueries in the statement

REPLACE INTO t1 SELECT * FROM t2 RETURNING (SELECT id2 FROM t2 WHERE 
id2 IN (SELECT id2 FROM t2 WHERE id2=1)) AS new_id;
+--------+
| new_id |
+--------+
|      1 |
|      1 |
|      1 |
|      1 |
+--------+

Subqueries in the RETURNING clause that return more than one row or column cannot be used..

Aggregate functions cannot be used in the RETURNING clause. Since aggregate functions work on a set of values and if the purpose is to get the row count, ROW_COUNT() with SELECT can be used, or it can be used in REPLACE...SELECT...RETURNING if the table in the RETURNING clause is not the same as the REPLACE table. ECT...RETURNING if the table in the RETURNING clause is not the same as the REPLACE table.

See Also

1.1.1.2.1.16 SHOW COLUMNS

Syntax

SHOW [FULL] {COLUMNS | FIELDS} FROM tbl_name [FROM db_name]
    [LIKE 'pattern' | WHERE expr]

Contents

  1. Syntax
  2. Description
  3. Examples
  4. See Also

Description

SHOW COLUMNS displays information about the columns in a given table. It also works for views. The LIKE clause, if present on its own, indicates which column names to match. The WHERE and LIKE clauses can be given to select rows using more general conditions, as discussed in Extended SHOW.

If the data types differ from what you expect them to be based on a CREATE TABLE statement, note that MariaDB sometimes changes data types when you create or alter a table. The conditions under which this occurs are described in the Silent Column Changes article.

The FULL keyword causes the output to include the column collation and comments, as well as the privileges you have for each column.

You can use db_name.tbl_name as an alternative to the tbl_name FROM db_name syntax. In other words, these two statements are equivalent:

SHOW COLUMNS FROM mytable FROM mydb;
SHOW COLUMNS FROM mydb.mytable;

SHOW COLUMNS displays the following values for each table column:

Field indicates the column name.

Type indicates the column data type.

Collation indicates the collation for non-binary string columns, or NULL for other columns. This value is displayed only if you use the FULL keyword.

The Null field contains YES if NULL values can be stored in the column, NO if not.

The Key field indicates whether the column is indexed:

  • If Key is empty, the column either is not indexed or is indexed only as a secondary column in a multiple-column, non-unique index.
  • If Key is PRI, the column is a PRIMARY KEY or is one of the columns in a multiple-column PRIMARY KEY.
  • If Key is UNI, the column is the first column of a unique-valued index that cannot contain NULL values.
  • If Key is MUL, multiple occurrences of a given value are allowed within the column. The column is the first column of a non-unique index or a unique-valued index that can contain NULL values.

If more than one of the Key values applies to a given column of a table, Key displays the one with the highest priority, in the order PRI, UNI, MUL.

A UNIQUE index may be displayed as PRI if it cannot contain NULL values and there is no PRIMARY KEY in the table. A UNIQUE index may display as MUL if several columns form a composite UNIQUE index; although the combination of the columns is unique, each column can still hold multiple occurrences of a given value.

The Default field indicates the default value that is assigned to the column.

The Extra field contains any additional information that is available about a given column.

ValueDescription
AUTO_INCREMENTThe column was created with the AUTO_INCREMENT keyword.
PERSISTENTThe column was created with the PERSISTENT keyword. (New in 5.3)
VIRTUALThe column was created with the VIRTUAL keyword. (New in 5.3)
on update CURRENT_TIMESTAMPThe column is a TIMESTAMP column that is automatically updated on INSERT and UPDATE.

Privileges indicates the privileges you have for the column. This value is displayed only if you use the FULL keyword.

Comment indicates any comment the column has. This value is displayed only if you use the FULL keyword.

SHOW FIELDS is a synonym for SHOW COLUMNS. Also DESCRIBE and EXPLAIN can be used as shortcuts.

You can also list a table's columns with: 

mysqlshow db_name tbl_name

See the mysqlshow command for more details.

The DESCRIBE statement provides information similar to SHOW COLUMNS. The information_schema.COLUMNS table provides similar, but more complete, information.

The SHOW CREATE TABLE, SHOW TABLE STATUS, and SHOW INDEX statements also provide information about tables.

Examples

SHOW COLUMNS FROM city;
+------------+----------+------+-----+---------+----------------+
| Field      | Type     | Null | Key | Default | Extra          |
+------------+----------+------+-----+---------+----------------+
| Id         | int(11)  | NO   | PRI | NULL    | auto_increment |
| Name       | char(35) | NO   |     |         |                |
| Country    | char(3)  | NO   | UNI |         |                |
| District   | char(20) | YES  | MUL |         |                |
| Population | int(11)  | NO   |     | 0       |                |
+------------+----------+------+-----+---------+----------------+

SHOW COLUMNS FROM employees WHERE Type LIKE 'Varchar%';
+---------------+-------------+------+-----+---------+-------+
| Field         | Type        | Null | Key | Default | Extra |
+---------------+-------------+------+-----+---------+-------+
| first_name    | varchar(30) | NO   | MUL | NULL    |       |
| last_name     | varchar(40) | NO   |     | NULL    |       |
| position      | varchar(25) | NO   |     | NULL    |       |
| home_address  | varchar(50) | NO   |     | NULL    |       |
| home_phone    | varchar(12) | NO   |     | NULL    |       |
| employee_code | varchar(25) | NO   | UNI | NULL    |       |
+---------------+-------------+------+-----+---------+-------+

See Also

1.1.1.2.1.17 SHOW CREATE TABLE

Syntax

SHOW CREATE TABLE tbl_name

Contents

  1. Syntax
  2. Description
  3. Examples
  4. See Also

Description

Shows the CREATE TABLE statement that created the given table. The statement requires the SELECT privilege for the table. This statement also works with views and SEQUENCE.

SHOW CREATE TABLE quotes table and column names according to the value of the sql_quote_show_create server system variable.

Certain SQL_MODE values can result in parts of the original CREATE statement not being included in the output. MariaDB-specific table options, column options, and index options are not included in the output of this statement if the NO_TABLE_OPTIONS, NO_FIELD_OPTIONS and NO_KEY_OPTIONS SQL_MODE flags are used. All MariaDB-specific table attributes are also not shown when a non-MariaDB/MySQL emulation mode is used, which includes ANSI, DB2, POSTGRESQL, MSSQL, MAXDB or ORACLE.

Invalid table options, column options and index options are normally commented out (note, that it is possible to create a table with invalid options, by altering a table of a different engine, where these options were valid). To have them uncommented, enable the IGNORE_BAD_TABLE_OPTIONS SQL_MODE. Remember that replaying a CREATE TABLE statement with uncommented invalid options will fail with an error, unless the IGNORE_BAD_TABLE_OPTIONS SQL_MODE is in effect.

Note that SHOW CREATE TABLE is not meant to provide metadata about a table. It provides information about how the table was declared, but the real table structure could differ a bit. For example, if an index has been declared as HASH, the CREATE TABLE statement returned by SHOW CREATE TABLE will declare that index as HASH; however, it is possible that the index is in fact a BTREE, because the storage engine does not support HASH.

MariaDB starting with 10.2.1

MariaDB 10.2.1 permits TEXT and BLOB data types to be assigned a DEFAULT value. As a result, from MariaDB 10.2.1, SHOW CREATE TABLE will append a DEFAULT NULL to nullable TEXT or BLOB fields if no specific default is provided.

MariaDB starting with 10.2.2

From MariaDB 10.2.2, numbers are no longer quoted in the DEFAULT clause in SHOW CREATE statement. Previously, MariaDB quoted numbers.

Examples

SHOW CREATE TABLE t\G
*************************** 1. row ***************************
       Table: t
Create Table: CREATE TABLE `t` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `s` char(60) DEFAULT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1

With sql_quote_show_create off:

SHOW CREATE TABLE t\G
*************************** 1. row ***************************
       Table: t
Create Table: CREATE TABLE t (
  id int(11) NOT NULL AUTO_INCREMENT,
  s char(60) DEFAULT NULL,
  PRIMARY KEY (id)
) ENGINE=InnoDB DEFAULT CHARSET=latin1

Unquoted numeric DEFAULTs, from MariaDB 10.2.2:

CREATE TABLE td (link TINYINT DEFAULT 1);

SHOW CREATE TABLE td\G
*************************** 1. row ***************************
       Table: td
Create Table: CREATE TABLE `td` (
  `link` tinyint(4) DEFAULT 1
) ENGINE=InnoDB DEFAULT CHARSET=latin1

Quoted numeric DEFAULTs, until MariaDB 10.2.1:

CREATE TABLE td (link TINYINT DEFAULT 1);

SHOW CREATE TABLE td\G
*************************** 1. row ***************************
       Table: td
Create Table: CREATE TABLE `td` (
  `link` tinyint(4) DEFAULT '1'
) ENGINE=InnoDB DEFAULT CHARSET=latin1

SQL_MODE impacting the output:

SELECT @@sql_mode;
+-------------------------------------------------------------------------------------------+
| @@sql_mode                                                                                |
+-------------------------------------------------------------------------------------------+
| STRICT_TRANS_TABLES,ERROR_FOR_DIVISION_BY_ZERO,NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION |
+-------------------------------------------------------------------------------------------+

CREATE TABLE `t1` (
       `id` int(11) NOT NULL AUTO_INCREMENT,
       `msg` varchar(100) DEFAULT NULL,
       PRIMARY KEY (`id`)
     ) ENGINE=InnoDB DEFAULT CHARSET=latin1
;

SHOW CREATE TABLE t1\G
*************************** 1. row ***************************
       Table: t1
Create Table: CREATE TABLE `t1` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `msg` varchar(100) DEFAULT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1

SET SQL_MODE=ORACLE;

SHOW CREATE TABLE t1\G
*************************** 1. row ***************************
       Table: t1
Create Table: CREATE TABLE "t1" (
  "id" int(11) NOT NULL,
  "msg" varchar(100) DEFAULT NULL,
  PRIMARY KEY ("id")

See Also

1.1.1.2.1.18 SHOW INDEX

Syntax

SHOW {INDEX | INDEXES | KEYS} 
 FROM tbl_name [FROM db_name]
 [WHERE expr]

Contents

  1. Syntax
  2. Description
  3. Examples
  4. See Also

Description

SHOW INDEX returns table index information. The format resembles that of the SQLStatistics call in ODBC.

You can use db_name.tbl_name as an alternative to the tbl_name FROM db_name syntax. These two statements are equivalent:

SHOW INDEX FROM mytable FROM mydb;
SHOW INDEX FROM mydb.mytable;

SHOW KEYS and SHOW INDEXES are synonyms for SHOW INDEX.

You can also list a table's indexes with the mariadb-show/mysqlshow command: 

mysqlshow -k db_name tbl_name

The information_schema.STATISTICS table stores similar information.

The following fields are returned by SHOW INDEX.

FieldDescription
TableTable name
Non_unique1 if the index permits duplicate values, 0 if values must be unique.
Key_nameIndex name. The primary key is always named PRIMARY.
Seq_in_indexThe column's sequence in the index, beginning with 1.
Column_nameColumn name.
CollationEither A, if the column is sorted in ascending order in the index, or NULL if it's not sorted.
CardinalityEstimated number of unique values in the index. The cardinality statistics are calculated at various times, and can help the optimizer make improved decisions.
Sub_partNULL if the entire column is included in the index, or the number of included characters if not.
PackedNULL if the index is not packed, otherwise how the index is packed.
NullNULL if NULL values are permitted in the column, an empty string if NULL's are not permitted.
Index_typeThe index type, which can be BTREE, FULLTEXT, HASH or RTREE. See Storage Engine Index Types.
CommentOther information, such as whether the index is disabled.
Index_commentContents of the COMMENT attribute when the index was created.
IgnoredWhether or not an index will be ignored by the optimizer. See Ignored Indexes. From MariaDB 10.6.0.

The WHERE and LIKE clauses can be given to select rows using more general conditions, as discussed in Extended SHOW.

Examples

CREATE TABLE IF NOT EXISTS `employees_example` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `first_name` varchar(30) NOT NULL,
  `last_name` varchar(40) NOT NULL,
  `position` varchar(25) NOT NULL,
  `home_address` varchar(50) NOT NULL,
  `home_phone` varchar(12) NOT NULL,
  `employee_code` varchar(25) NOT NULL,
  PRIMARY KEY (`id`),
  UNIQUE KEY `employee_code` (`employee_code`),
  KEY `first_name` (`first_name`,`last_name`)
) ENGINE=Aria;

INSERT INTO `employees_example` (`first_name`, `last_name`, `position`, `home_address`, `home_phone`, `employee_code`)
  VALUES
  ('Mustapha', 'Mond', 'Chief Executive Officer', '692 Promiscuous Plaza', '326-555-3492', 'MM1'),
  ('Henry', 'Foster', 'Store Manager', '314 Savage Circle', '326-555-3847', 'HF1'),
  ('Bernard', 'Marx', 'Cashier', '1240 Ambient Avenue', '326-555-8456', 'BM1'),
  ('Lenina', 'Crowne', 'Cashier', '281 Bumblepuppy Boulevard', '328-555-2349', 'LC1'),
  ('Fanny', 'Crowne', 'Restocker', '1023 Bokanovsky Lane', '326-555-6329', 'FC1'),
  ('Helmholtz', 'Watson', 'Janitor', '944 Soma Court', '329-555-2478', 'HW1');

SHOW INDEXES FROM employees_example\G
*************************** 1. row ***************************
        Table: employees_example
   Non_unique: 0
     Key_name: PRIMARY
 Seq_in_index: 1
  Column_name: id
    Collation: A
  Cardinality: 6
     Sub_part: NULL
       Packed: NULL
         Null: 
   Index_type: BTREE
      Comment: 
Index_comment: 
      Ignored: NO
*************************** 2. row ***************************
        Table: employees_example
   Non_unique: 0
     Key_name: employee_code
 Seq_in_index: 1
  Column_name: employee_code
    Collation: A
  Cardinality: 6
     Sub_part: NULL
       Packed: NULL
         Null: 
   Index_type: BTREE
      Comment: 
Index_comment: 
      Ignored: NO
*************************** 3. row ***************************
        Table: employees_example
   Non_unique: 1
     Key_name: first_name
 Seq_in_index: 1
  Column_name: first_name
    Collation: A
  Cardinality: NULL
     Sub_part: NULL
       Packed: NULL
         Null: 
   Index_type: BTREE
      Comment: 
Index_comment: 
      Ignored: NO
*************************** 4. row ***************************
        Table: employees_example
   Non_unique: 1
     Key_name: first_name
 Seq_in_index: 2
  Column_name: last_name
    Collation: A
  Cardinality: NULL
     Sub_part: NULL
       Packed: NULL
         Null: 
   Index_type: BTREE
      Comment: 
Index_comment: 
      Ignored: NO

See Also

1.1.1.2.1.19 TRUNCATE TABLE

Syntax

TRUNCATE [TABLE] tbl_name
  [WAIT n | NOWAIT]

Contents

  1. Syntax
  2. Description
    1. WAIT/NOWAIT
    2. Oracle-mode
    3. Performance
  3. See Also

Description

TRUNCATE TABLE empties a table completely. It requires the DROP privilege. See GRANT.

tbl_name can also be specified in the form db_name.tbl_name (see Identifier Qualifiers).

Logically, TRUNCATE TABLE is equivalent to a DELETE statement that deletes all rows, but there are practical differences under some circumstances.

TRUNCATE TABLE will fail for an InnoDB table if any FOREIGN KEY constraints from other tables reference the table, returning the error:

ERROR 1701 (42000): Cannot truncate a table referenced in a foreign key constraint

Foreign Key constraints between columns in the same table are permitted.

For an InnoDB table, if there are no FOREIGN KEY constraints, InnoDB performs fast truncation by dropping the original table and creating an empty one with the same definition, which is much faster than deleting rows one by one. The AUTO_INCREMENT counter is reset by TRUNCATE TABLE, regardless of whether there is a FOREIGN KEY constraint.

The count of rows affected by TRUNCATE TABLE is accurate only when it is mapped to a DELETE statement.

For other storage engines, TRUNCATE TABLE differs from DELETE in the following ways:

  • Truncate operations drop and re-create the table, which is much faster than deleting rows one by one, particularly for large tables.
  • Truncate operations cause an implicit commit.
  • Truncation operations cannot be performed if the session holds an active table lock.
  • Truncation operations do not return a meaningful value for the number of deleted rows. The usual result is "0 rows affected," which should be interpreted as "no information."
  • As long as the table format file tbl_name.frm is valid, the table can be re-created as an empty table with TRUNCATE TABLE, even if the data or index files have become corrupted.
  • The table handler does not remember the last used AUTO_INCREMENT value, but starts counting from the beginning. This is true even for MyISAM and InnoDB, which normally do not reuse sequence values.
  • When used with partitioned tables, TRUNCATE TABLE preserves the partitioning; that is, the data and index files are dropped and re-created, while the partition definitions (.par) file is unaffected.
  • Since truncation of a table does not make any use of DELETE, the TRUNCATE statement does not invoke ON DELETE triggers.
  • TRUNCATE TABLE will only reset the values in the Performance Schema summary tables to zero or null, and will not remove the rows.

For the purposes of binary logging and replication, TRUNCATE TABLE is treated as DROP TABLE followed by CREATE TABLE (DDL rather than DML).

TRUNCATE TABLE does not work on views. Currently, TRUNCATE TABLE drops all historical records from a system-versioned table.

MariaDB starting with 10.3.0

WAIT/NOWAIT

Set the lock wait timeout. See WAIT and NOWAIT.

Oracle-mode

Oracle-mode from MariaDB 10.3 permits the optional keywords REUSE STORAGE or DROP STORAGE to be used.

TRUNCATE [TABLE] tbl_name [{DROP | REUSE} STORAGE] [WAIT n | NOWAIT]

These have no effect on the operation.

Performance

TRUNCATE TABLE is faster than DELETE, because it drops and re-creates a table.

With InnoDB, TRUNCATE TABLE is slower if innodb_file_per_table=ON is set (the default). This is because TRUNCATE TABLE unlinks the underlying tablespace file, which can be an expensive operation. See MDEV-8069 for more details.

The performance issues with innodb_file_per_table=ON can be exacerbated in cases where the InnoDB buffer pool is very large and innodb_adaptive_hash_index=ON is set. In that case, using DROP TABLE followed by CREATE TABLE instead of TRUNCATE TABLE may perform better. Setting innodb_adaptive_hash_index=OFF (it defaults to ON before MariaDB 10.5) can also help. In MariaDB 10.2 only, from MariaDB 10.2.19, this performance can also be improved by setting innodb_safe_truncate=OFF. See MDEV-9459 for more details.

Setting innodb_adaptive_hash_index=OFF can also improve TRUNCATE TABLE performance in general. See MDEV-16796 for more details.

See Also

1.1.1.2.1.20 UPDATE

Syntax

Single-table syntax:

UPDATE [LOW_PRIORITY] [IGNORE] table_reference 
  [PARTITION (partition_list)]
  [FOR PORTION OF period FROM expr1 TO expr2]
  SET col1={expr1|DEFAULT} [,col2={expr2|DEFAULT}] ...
  [WHERE where_condition]
  [ORDER BY ...]
  [LIMIT row_count]

Multiple-table syntax:

UPDATE [LOW_PRIORITY] [IGNORE] table_references
    SET col1={expr1|DEFAULT} [, col2={expr2|DEFAULT}] ...
    [WHERE where_condition]

Contents

  1. Syntax
  2. Description
    1. PARTITION
    2. FOR PORTION OF
    3. UPDATE Statements With the Same Source and Target
  3. Example
  4. See Also

Description

For the single-table syntax, the UPDATE statement updates columns of existing rows in the named table with new values. The SET clause indicates which columns to modify and the values they should be given. Each value can be given as an expression, or the keyword DEFAULT to set a column explicitly to its default value. The WHERE clause, if given, specifies the conditions that identify which rows to update. With no WHERE clause, all rows are updated. If the ORDER BY clause is specified, the rows are updated in the order that is specified. The LIMIT clause places a limit on the number of rows that can be updated.

Until MariaDB 10.3.2, for the multiple-table syntax, UPDATE updates rows in each table named in table_references that satisfy the conditions. In this case, ORDER BY and LIMIT cannot be used. This restriction was lifted in MariaDB 10.3.2 and both clauses can be used with multiple-table updates. An UPDATE can also reference tables which are located in different databases; see Identifier Qualifiers for the syntax.

where_condition is an expression that evaluates to true for each row to be updated.

table_references and where_condition are as specified as described in SELECT.

For single-table updates, assignments are evaluated in left-to-right order, while for multi-table updates, there is no guarantee of a particular order. If the SIMULTANEOUS_ASSIGNMENT sql_mode (available from MariaDB 10.3.5) is set, UPDATE statements evaluate all assignments simultaneously.

You need the UPDATE privilege only for columns referenced in an UPDATE that are actually updated. You need only the SELECT privilege for any columns that are read but not modified. See GRANT.

The UPDATE statement supports the following modifiers:

  • If you use the LOW_PRIORITY keyword, execution of the UPDATE is delayed until no other clients are reading from the table. This affects only storage engines that use only table-level locking (MyISAM, MEMORY, MERGE). See HIGH_PRIORITY and LOW_PRIORITY clauses for details.
  • If you use the IGNORE keyword, the update statement does not abort even if errors occur during the update. Rows for which duplicate-key conflicts occur are not updated. Rows for which columns are updated to values that would cause data conversion errors are updated to the closest valid values instead.

PARTITION

See Partition Pruning and Selection for details.

FOR PORTION OF

MariaDB starting with 10.4.3

See Application Time Periods - Updating by Portion.

UPDATE Statements With the Same Source and Target

MariaDB starting with 10.3.2

From MariaDB 10.3.2, UPDATE statements may have the same source and target.

For example, given the following table:

DROP TABLE t1;
CREATE TABLE t1 (c1 INT, c2 INT);
INSERT INTO t1 VALUES (10,10), (20,20);

Until MariaDB 10.3.1, the following UPDATE statement would not work:

UPDATE t1 SET c1=c1+1 WHERE c2=(SELECT MAX(c2) FROM t1);
ERROR 1093 (HY000): Table 't1' is specified twice, 
  both as a target for 'UPDATE' and as a separate source for data

From MariaDB 10.3.2, the statement executes successfully:

UPDATE t1 SET c1=c1+1 WHERE c2=(SELECT MAX(c2) FROM t1);

SELECT * FROM t1;
+------+------+
| c1   | c2   |
+------+------+
|   10 |   10 |
|   21 |   20 |
+------+------+

Example

Single-table syntax:

UPDATE table_name SET column1 = value1, column2 = value2 WHERE id=100;

Multiple-table syntax:

UPDATE tab1, tab2 SET tab1.column1 = value1, tab1.column2 = value2 WHERE tab1.id = tab2.id;

See Also

1.1.1.2.1.21 IGNORE

The IGNORE option tells the server to ignore some common errors.

IGNORE can be used with the following statements:

The logic used:

  • Variables out of ranges are replaced with the maximum/minimum value.
  • SQL_MODEs STRICT_TRANS_TABLES, STRICT_ALL_TABLES, NO_ZERO_IN_DATE, NO_ZERO_DATE are ignored.
  • Inserting NULL in a NOT NULL field will insert 0 ( in a numerical field), 0000-00-00 ( in a date field) or an empty string ( in a character field).
  • Rows that cause a duplicate key error or break a foreign key constraint are not inserted, updated, or deleted.

The following errors are ignored:

Error numberSymbolic error nameDescription
1022ER_DUP_KEYCan't write; duplicate key in table '%s'
1048ER_BAD_NULL_ERRORColumn '%s' cannot be null
1062ER_DUP_ENTRYDuplicate entry '%s' for key %d
1242ER_SUBQUERY_NO_1_ROWSubquery returns more than 1 row
1264ER_WARN_DATA_OUT_OF_RANGEOut of range value for column '%s' at row %ld
1265WARN_DATA_TRUNCATEDData truncated for column '%s' at row %ld
1292ER_TRUNCATED_WRONG_VALUETruncated incorrect %s value: '%s'
1366ER_TRUNCATED_WRONG_VALUE_FOR_FIELDIncorrect integer value
1369ER_VIEW_CHECK_FAILEDCHECK OPTION failed '%s.%s'
1451ER_ROW_IS_REFERENCED_2Cannot delete or update a parent row
1452ER_NO_REFERENCED_ROW_2Cannot add or update a child row: a foreign key constraint fails (%s)
1526ER_NO_PARTITION_FOR_GIVEN_VALUETable has no partition for value %s
1586ER_DUP_ENTRY_WITH_KEY_NAMEDuplicate entry '%s' for key '%s'
1591ER_NO_PARTITION_FOR_GIVEN_VALUE_SILENTTable has no partition for some existing values
1748ER_ROW_DOES_NOT_MATCH_GIVEN_PARTITION_SETFound a row not matching the given partition set

Ignored errors normally generate a warning.

A property of the IGNORE clause consists in causing transactional engines and non-transactional engines (like XtraDB and Aria) to behave the same way. For example, normally a multi-row insert which tries to violate a UNIQUE contraint is completely rolled back on XtraDB/InnoDB, but might be partially executed on Aria. With the IGNORE clause, the statement will be partially executed in both engines.

Duplicate key errors also generate warnings. The OLD_MODE server variable can be used to prevent this.

1.1.1.2.1.22 System-Versioned Tables

1.1.1.2.2 ANALYZE and EXPLAIN Statements

1.1.1.2.2.1 ANALYZE FORMAT=JSON

Contents

  1. Basic Execution Data
  2. Advanced Execution Data
  3. Data About Individual Query Plan Nodes
  4. Use Cases

ANALYZE FORMAT=JSON is a mix of the EXPLAIN FORMAT=JSON and ANALYZE statement features. The ANALYZE FORMAT=JSON $statement will execute $statement, and then print the output of EXPLAIN FORMAT=JSON, amended with data from the query execution.

Basic Execution Data

You can get the following also from tabular ANALYZE statement form:

  • r_rows is provided for any node that reads rows. It shows how many rows were read, on average
  • r_filtered is provided whenever there is a condition that is checked. It shows the percentage of rows left after checking the condition.

Advanced Execution Data

The most important data not available in the regular tabula ANALYZE statement are:

  • r_loops field. This shows how many times the node was executed. Most query plan elements have this field.
  • r_total_time_ms field. It shows how much time in total was spent executing this node. If the node has subnodes, their execution time is included.
  • r_buffer_size field. Query plan nodes that make use of buffers report the size of buffer that was was used.

Data About Individual Query Plan Nodes

  • filesort node reports whether sorting was done with LIMIT n parameter, and how many rows were in the sort result.
  • block-nl-join node has r_loops field, which allows to tell whether Using join buffer was efficient
  • range-checked-for-each-record reports counters that show the result of the check.
  • expression-cache is used for subqueries, and it reports how many times the cache was used, and what cache hit ratio was.
  • union_result node has r_rows so one can see how many rows were produced after UNION operation
  • and so forth

Use Cases

See Examples of ANALYZE FORMAT=JSON.

1.1.1.2.2.2 ANALYZE FORMAT=JSON Examples

Example #1

Customers who have ordered more than 1M goods.

ANALYZE FORMAT=JSON
SELECT COUNT(*)
FROM customer
WHERE
  (SELECT SUM(o_totalprice) FROM orders WHERE o_custkey=c_custkey) > 1000*1000;

The query takes 40 seconds over cold cache

EXPLAIN: {
  "query_block": {
    "select_id": 1,
    "r_loops": 1,
    "r_total_time_ms": 39872,
    "table": {
      "table_name": "customer",
      "access_type": "index",
      "key": "i_c_nationkey",
      "key_length": "5",
      "used_key_parts": ["c_nationkey"],
      "r_loops": 1,
      "rows": 150303,
      "r_rows": 150000,
      "r_total_time_ms": 270.3,
      "filtered": 100,
      "r_filtered": 60.691,
      "attached_condition": "((subquery#2) > <cache>((1000 * 1000)))",
      "using_index": true
    },
    "subqueries": [
      {
        "query_block": {
          "select_id": 2,
          "r_loops": 150000,
          "r_total_time_ms": 39531,
          "table": {
            "table_name": "orders",
            "access_type": "ref",
            "possible_keys": ["i_o_custkey"],
            "key": "i_o_custkey",
            "key_length": "5",
            "used_key_parts": ["o_custkey"],
            "ref": ["dbt3sf1.customer.c_custkey"],
            "r_loops": 150000,
            "rows": 7,
            "r_rows": 10,
            "r_total_time_ms": 39208,
            "filtered": 100,
            "r_filtered": 100
          }
        }
      }
    ]
  }
}

ANALYZE shows that 39.2 seconds were spent in the subquery, which was executed 150K times (for every row of outer table).

1.1.1.2.2.3 ANALYZE Statement

Contents

  1. Description
  2. Command Output
  3. Interpreting the Output
    1. Joins
    2. Meaning of NULL in r_rows and r_filtered
  4. ANALYZE FORMAT=JSON
  5. Notes
  6. See Also

Description

The ANALYZE statement is similar to the EXPLAIN statement. ANALYZE statement will invoke the optimizer, execute the statement, and then produce EXPLAIN output instead of the result set. The EXPLAIN output will be annotated with statistics from statement execution.

This lets one check how close the optimizer's estimates about the query plan are to the reality. ANALYZE produces an overview, while the ANALYZE FORMAT=JSON command provides a more detailed view of the query plan and the query execution.

The syntax is 

ANALYZE explainable_statement;

where the statement is any statement for which one can run EXPLAIN.

Command Output

Consider an example:

ANALYZE SELECT * FROM tbl1 
WHERE key1 
  BETWEEN 10 AND 200 AND 
  col1 LIKE 'foo%'\G

*************************** 1. row ***************************
           id: 1
  select_type: SIMPLE
        table: tbl1
         type: range
possible_keys: key1
          key: key1
      key_len: 5
          ref: NULL
         rows: 181
       r_rows: 181
     filtered: 100.00
   r_filtered: 10.50
        Extra: Using index condition; Using where

Compared to EXPLAIN, ANALYZE produces two extra columns:

  • r_rows is an observation-based counterpart of the rows column. It shows how many rows were actually read from the table.
  • r_filtered is an observation-based counterpart of the filtered column. It shows which fraction of rows was left after applying the WHERE condition.

Interpreting the Output

Joins

Let's consider a more complicated example.

ANALYZE SELECT *
FROM orders, customer 
WHERE
  customer.c_custkey=orders.o_custkey AND
  customer.c_acctbal < 0 AND
  orders.o_totalprice > 200*1000

+----+-------------+----------+------+---------------+-------------+---------+--------------------+--------+--------+----------+------------+-------------+
| id | select_type | table    | type | possible_keys | key         | key_len | ref                | rows   | r_rows | filtered | r_filtered | Extra       |
+----+-------------+----------+------+---------------+-------------+---------+--------------------+--------+--------+----------+------------+-------------+
|  1 | SIMPLE      | customer | ALL  | PRIMARY,...   | NULL        | NULL    | NULL               | 149095 | 150000 |    18.08 |       9.13 | Using where |
|  1 | SIMPLE      | orders   | ref  | i_o_custkey   | i_o_custkey | 5       | customer.c_custkey |      7 |     10 |   100.00 |      30.03 | Using where |
+----+-------------+----------+------+---------------+-------------+---------+--------------------+--------+--------+----------+------------+-------------+

Here, one can see that

  • For table customer, customer.rows=149095, customer.r_rows=150000. The estimate for number of rows we will read was fairly precise
  • customer.filtered=18.08, customer.r_filtered=9.13. The optimizer somewhat overestimated the number of records that will match selectivity of condition attached to `customer` table (in general, when you have a full scan and r_filtered is less than 15%, it's time to consider adding an appropriate index).
  • For table orders, orders.rows=7, orders.r_rows=10. This means that on average, there are 7 orders for a given c_custkey, but in our case there were 10, which is close to the expectation (when this number is consistently far from the expectation, it may be time to run ANALYZE TABLE, or even edit the table statistics manually to get better query plans).
  • orders.filtered=100, orders.r_filtered=30.03. The optimizer didn't have any way to estimate which fraction of records will be left after it checks the condition that is attached to table orders (it's orders.o_totalprice > 200*1000). So, it used 100%. In reality, it is 30%. 30% is typically not selective enough to warrant adding new indexes. For joins with many tables, it might be worth to collect and use column statistics for columns in question, this may help the optimizer to pick a better query plan.

Meaning of NULL in r_rows and r_filtered

Let's modify the previous example slightly

ANALYZE SELECT * 
FROM orders, customer 
WHERE
  customer.c_custkey=orders.o_custkey AND
  customer.c_acctbal < -0 AND 
  customer.c_comment LIKE '%foo%' AND
  orders.o_totalprice > 200*1000;

+----+-------------+----------+------+---------------+-------------+---------+--------------------+--------+--------+----------+------------+-------------+
| id | select_type | table    | type | possible_keys | key         | key_len | ref                | rows   | r_rows | filtered | r_filtered | Extra       |
+----+-------------+----------+------+---------------+-------------+---------+--------------------+--------+--------+----------+------------+-------------+
|  1 | SIMPLE      | customer | ALL  | PRIMARY,...   | NULL        | NULL    | NULL               | 149095 | 150000 |    18.08 |       0.00 | Using where |
|  1 | SIMPLE      | orders   | ref  | i_o_custkey   | i_o_custkey | 5       | customer.c_custkey |      7 |   NULL |   100.00 |       NULL | Using where |
+----+-------------+----------+------+---------------+-------------+---------+--------------------+--------+--------+----------+------------+-------------+

Here, one can see that orders.r_rows=NULL and orders.r_filtered=NULL. This means that table orders was not scanned even once. Indeed, we can also see customer.r_filtered=0.00. This shows that a part of WHERE attached to table `customer` was never satisfied (or, satisfied in less than 0.01% of cases).

ANALYZE FORMAT=JSON

ANALYZE FORMAT=JSON produces JSON output. It produces much more information than tabular ANALYZE.

Notes

  • ANALYZE UPDATE or ANALYZE DELETE will actually make updates/deletes (ANALYZE SELECT will perform the select operation and then discard the resultset).
  • PostgreSQL has a similar command, EXPLAIN ANALYZE.
  • The EXPLAIN in the slow query log feature allows MariaDB to have ANALYZE output of slow queries printed into the slow query log (see MDEV-6388).

See Also

1.1.1.2.2.4 EXPLAIN

Syntax

EXPLAIN tbl_name

Or

EXPLAIN [EXTENDED | PARTITIONS] 
  {SELECT select_options | UPDATE update_options | DELETE delete_options}

Contents

  1. Syntax
  2. Description
    1. Columns in EXPLAIN ... SELECT
      1. "Select_type" Column
      2. "Type" Column
      3. "Extra" Column
    2. EXPLAIN EXTENDED
  3. Examples
    1. Example of ref_or_null Optimization
  4. See Also

Description

The EXPLAIN statement can be used either as a synonym for DESCRIBE or as a way to obtain information about how MariaDB executes a SELECT, UPDATE or DELETE statement:

  • 'EXPLAIN tbl_name' is synonymous with 'DESCRIBE tbl_name' or 'SHOW COLUMNS FROM tbl_name'.
  • When you precede a SELECT, UPDATE or a DELETE statement with the keyword EXPLAIN, MariaDB displays information from the optimizer about the query execution plan. That is, MariaDB explains how it would process the SELECT, UPDATE or DELETE, including information about how tables are joined and in which order. EXPLAIN EXTENDED can be used to provide additional information.
  • EXPLAIN PARTITIONS is useful only when examining queries involving partitioned tables.
    For details, see Partition pruning and selection.
  • ANALYZE statement performs the query as well as producing EXPLAIN output, and provides actual as well as estimated statistics.
  • EXPLAIN output can be printed in the slow query log. See EXPLAIN in the Slow Query Log for details.

SHOW EXPLAIN shows the output of a running statement. In some cases, its output can be closer to reality than EXPLAIN.

The ANALYZE statement runs a statement and returns information about its execution plan. It also shows additional columns, to check how much the optimizer's estimation about filtering and found rows are close to reality.

There is an online EXPLAIN Analyzer that you can use to share EXPLAIN and EXPLAIN EXTENDED output with others.

EXPLAIN can acquire metadata locks in the same way that SELECT does, as it needs to know table metadata and, sometimes, data as well.

Columns in EXPLAIN ... SELECT

Column nameDescription
idSequence number that shows in which order tables are joined.
select_typeWhat kind of SELECT the table comes from.
tableAlias name of table. Materialized temporary tables for sub queries are named <subquery#>
typeHow rows are found from the table (join type).
possible_keyskeys in table that could be used to find rows in the table
keyThe name of the key that is used to retrieve rows. NULL is no key was used.
key_lenHow many bytes of the key that was used (shows if we are using only parts of the multi-column key).
refThe reference that is used as the key value.
rowsAn estimate of how many rows we will find in the table for each key lookup.
ExtraExtra information about this join.

Here are descriptions of the values for some of the more complex columns in EXPLAIN ... SELECT:

"Select_type" Column

The select_type column can have the following values:

ValueDescriptionComment
DEPENDENT SUBQUERYThe SUBQUERY is DEPENDENT.
DEPENDENT UNIONThe UNION is DEPENDENT.
DERIVEDThe SELECT is DERIVED from the PRIMARY.
MATERIALIZEDThe SUBQUERY is MATERIALIZED.Materialized tables will be populated at first access and will be accessed by the primary key (= one key lookup). Number of rows in EXPLAIN shows the cost of populating the table
PRIMARYThe SELECT is a PRIMARY one.
SIMPLEThe SELECT is a SIMPLE one.
SUBQUERYThe SELECT is a SUBQUERY of the PRIMARY.
UNCACHEABLE SUBQUERYThe SUBQUERY is UNCACHEABLE.
UNCACHEABLE UNIONThe UNION is UNCACHEABLE.
UNIONThe SELECT is a UNION of the PRIMARY.
UNION RESULTThe result of the UNION.
LATERAL DERIVEDThe SELECT uses a Lateral Derived optimization

"Type" Column

This column contains information on how the table is accessed.

ValueDescription
ALLA full table scan is done for the table (all rows are read). This is bad if the table is large and the table is joined against a previous table! This happens when the optimizer could not find any usable index to access rows.
constThere is only one possibly matching row in the table. The row is read before the optimization phase and all columns in the table are treated as constants.
eq_refA unique index is used to find the rows. This is the best possible plan to find the row.
fulltextA fulltext index is used to access the rows.
index_mergeA 'range' access is done for for several index and the found rows are merged. The key column shows which keys are used.
index_subqueryThis is similar as ref, but used for sub queries that are transformed to key lookups.
indexA full scan over the used index. Better than ALL but still bad if index is large and the table is joined against a previous table.
rangeThe table will be accessed with a key over one or more value ranges.
ref_or_nullLike 'ref' but in addition another search for the 'null' value is done if the first value was not found. This happens usually with sub queries.
refA non unique index or prefix of an unique index is used to find the rows. Good if the prefix doesn't match many rows.
systemThe table has 0 or 1 rows.
unique_subqueryThis is similar as eq_ref, but used for sub queries that are transformed to key lookups

"Extra" Column

This column consists of one or more of the following values, separated by ';'

Note that some of these values are detected after the optimization phase.

The optimization phase can do the following changes to the WHERE clause:

  • Add the expressions from the ON and USING clauses to the WHERE clause.
  • Constant propagation: If there is column=constant, replace all column instances with this constant.
  • Replace all columns from 'const' tables with their values.
  • Remove the used key columns from the WHERE (as this will be tested as part of the key lookup).
  • Remove impossible constant sub expressions. For example WHERE '(a=1 and a=2) OR b=1' becomes 'b=1'.
  • Replace columns with other columns that has identical values: Example: WHERE a=b and a=c may be treated as 'WHERE a=b and a=c and b=c'.
  • Add extra conditions to detect impossible row conditions earlier. This happens mainly with OUTER JOIN where we in some cases add detection of NULL values in the WHERE (Part of 'Not exists' optimization). This can cause an unexpected 'Using where' in the Extra column.
  • For each table level we remove expressions that have already been tested when we read the previous row. Example: When joining tables t1 with t2 using the following WHERE 't1.a=1 and t1.a=t2.b', we don't have to test 't1.a=1' when checking rows in t2 as we already know that this expression is true.
ValueDescription
const row not foundThe table was a system table (a table with should exactly one row), but no row was found.
DistinctIf distinct optimization (remove duplicates) was used. This is marked only for the last table in the SELECT.
Full scan on NULL keyThe table is a part of the sub query and if the value that is used to match the sub query will be NULL, we will do a full table scan.
Impossible HAVINGThe used HAVING clause is always false so the SELECT will return no rows.
Impossible WHERE noticed after reading const tables.The used WHERE clause is always false so the SELECT will return no rows. This case was detected after we had read all 'const' tables and used the column values as constant in the WHERE clause. For example: WHERE const_column=5 and const_column had a value of 4.
Impossible WHEREThe used WHERE clause is always false so the SELECT will return no rows. For example: WHERE 1=2
No matching min/max rowDuring early optimization of MIN()/MAX() values it was detected that no row could match the WHERE clause. The MIN()/MAX() function will return NULL.
no matching row in const tableThe table was a const table (a table with only one possible matching row), but no row was found.
No tables usedThe SELECT was a sub query that did not use any tables. For example a there was no FROM clause or a FROM DUAL clause.
Not existsStop searching after more row if we find one single matching row. This optimization is used with LEFT JOIN where one is explicitly searching for rows that doesn't exists in the LEFT JOIN TABLE. Example: SELECT * FROM t1 LEFT JOIN t2 on (...) WHERE t2.not_null_column IS NULL. As t2.not_null_column can only be NULL if there was no matching row for on condition, we can stop searching if we find a single matching row.
Open_frm_onlyFor information_schema tables. Only the frm (table definition file was opened) was opened for each matching row.
Open_full_tableFor information_schema tables. A full table open for each matching row is done to retrieve the requested information. (Slow)
Open_trigger_onlyFor information_schema tables. Only the trigger file definition was opened for each matching row.
Range checked for each record (index map: ...)This only happens when there was no good default index to use but there may some index that could be used when we can treat all columns from previous table as constants. For each row combination the optimizer will decide which index to use (if any) to fetch a row from this table. This is not fast, but faster than a full table scan that is the only other choice. The index map is a bitmask that shows which index are considered for each row condition.
Scanned 0/1/all databasesFor information_schema tables. Shows how many times we had to do a directory scan.
Select tables optimized awayAll tables in the join was optimized away. This happens when we are only using COUNT(*), MIN() and MAX() functions in the SELECT and we where able to replace all of these with constants.
Skip_open_tableFor information_schema tables. The queried table didn't need to be opened.
unique row not foundThe table was detected to be a const table (a table with only one possible matching row) during the early optimization phase, but no row was found.
Using filesortFilesort is needed to resolve the query. This means an extra phase where we first collect all columns to sort, sort them with a disk based merge sort and then use the sorted set to retrieve the rows in sorted order. If the column set is small, we store all the columns in the sort file to not have to go to the database to retrieve them again.
Using indexOnly the index is used to retrieve the needed information from the table. There is no need to perform an extra seek to retrieve the actual record.
Using index conditionLike 'Using where' but the where condition is pushed down to the table engine for internal optimization at the index level.
Using index condition(BKA)Like 'Using index condition' but in addition we use batch key access to retrieve rows.
Using index for group-byThe index is being used to resolve a GROUP BY or DISTINCT query. The rows are not read. This is very efficient if the table has a lot of identical index entries as duplicates are quickly jumped over.
Using intersect(...)For index_merge joins. Shows which index are part of the intersect.
Using join bufferWe store previous row combinations in a row buffer to be able to match each row against all of the rows combinations in the join buffer at one go.
Using sort_union(...)For index_merge joins. Shows which index are part of the union.
Using temporaryA temporary table is created to hold the result. This typically happens if you are using GROUP BY, DISTINCT or ORDER BY.
Using whereA WHERE expression (in additional to the possible key lookup) is used to check if the row should be accepted. If you don't have 'Using where' together with a join type of ALL, you are probably doing something wrong!
Using where with pushed conditionLike 'Using where' but the where condition is pushed down to the table engine for internal optimization at the row level.
Using bufferThe UPDATE statement will first buffer the rows, and then run the updates, rather than do updates on the fly. See Using Buffer UPDATE Algorithm for a detailed explanation.

EXPLAIN EXTENDED

The EXTENDED keyword adds another column, filtered, to the output. This is a percentage estimate of the table rows that will be filtered by the condition.

An EXPLAIN EXTENDED will always throw a warning, as it adds extra Message information to a subsequent SHOW WARNINGS statement. This includes what the SELECT query would look like after optimizing and rewriting rules are applied and how the optimizer qualifies columns and tables.

Examples

As synonym for DESCRIBE or SHOW COLUMNS FROM:

DESCRIBE city;
+------------+----------+------+-----+---------+----------------+
| Field      | Type     | Null | Key | Default | Extra          |
+------------+----------+------+-----+---------+----------------+
| Id         | int(11)  | NO   | PRI | NULL    | auto_increment |
| Name       | char(35) | YES  |     | NULL    |                |
| Country    | char(3)  | NO   | UNI |         |                |
| District   | char(20) | YES  | MUL |         |                |
| Population | int(11)  | YES  |     | NULL    |                |
+------------+----------+------+-----+---------+----------------+

A simple set of examples to see how EXPLAIN can identify poor index usage:

CREATE TABLE IF NOT EXISTS `employees_example` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `first_name` varchar(30) NOT NULL,
  `last_name` varchar(40) NOT NULL,
  `position` varchar(25) NOT NULL,
  `home_address` varchar(50) NOT NULL,
  `home_phone` varchar(12) NOT NULL,
  `employee_code` varchar(25) NOT NULL,
  PRIMARY KEY (`id`),
  UNIQUE KEY `employee_code` (`employee_code`),
  KEY `first_name` (`first_name`,`last_name`)
) ENGINE=Aria;

INSERT INTO `employees_example` (`first_name`, `last_name`, `position`, `home_address`, `home_phone`, `employee_code`)
  VALUES
  ('Mustapha', 'Mond', 'Chief Executive Officer', '692 Promiscuous Plaza', '326-555-3492', 'MM1'),
  ('Henry', 'Foster', 'Store Manager', '314 Savage Circle', '326-555-3847', 'HF1'),
  ('Bernard', 'Marx', 'Cashier', '1240 Ambient Avenue', '326-555-8456', 'BM1'),
  ('Lenina', 'Crowne', 'Cashier', '281 Bumblepuppy Boulevard', '328-555-2349', 'LC1'),
  ('Fanny', 'Crowne', 'Restocker', '1023 Bokanovsky Lane', '326-555-6329', 'FC1'),
  ('Helmholtz', 'Watson', 'Janitor', '944 Soma Court', '329-555-2478', 'HW1');

SHOW INDEXES FROM employees_example;
+-------------------+------------+---------------+--------------+---------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
| Table             | Non_unique | Key_name      | Seq_in_index | Column_name   | Collation | Cardinality | Sub_part | Packed | Null | Index_type | Comment | Index_comment |
+-------------------+------------+---------------+--------------+---------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
| employees_example |          0 | PRIMARY       |            1 | id            | A         |           7 |     NULL | NULL   |      | BTREE      |         |               |
| employees_example |          0 | employee_code |            1 | employee_code | A         |           7 |     NULL | NULL   |      | BTREE      |         |               |
| employees_example |          1 | first_name    |            1 | first_name    | A         |        NULL |     NULL | NULL   |      | BTREE      |         |               |
| employees_example |          1 | first_name    |            2 | last_name     | A         |        NULL |     NULL | NULL   |      | BTREE      |         |               |
+-------------------+------------+---------------+--------------+---------------+-----------+-------------+----------+--------+------+------------+---------+---------------+

SELECT on a primary key:

EXPLAIN SELECT * FROM employees_example WHERE id=1;
+------+-------------+-------------------+-------+---------------+---------+---------+-------+------+-------+
| id   | select_type | table             | type  | possible_keys | key     | key_len | ref   | rows | Extra |
+------+-------------+-------------------+-------+---------------+---------+---------+-------+------+-------+
|    1 | SIMPLE      | employees_example | const | PRIMARY       | PRIMARY | 4       | const |    1 |       |
+------+-------------+-------------------+-------+---------------+---------+---------+-------+------+-------+

The type is const, which means that only one possible result could be returned. Now, returning the same record but searching by their phone number:

EXPLAIN SELECT * FROM employees_example WHERE home_phone='326-555-3492';
+------+-------------+-------------------+------+---------------+------+---------+------+------+-------------+
| id   | select_type | table             | type | possible_keys | key  | key_len | ref  | rows | Extra       |
+------+-------------+-------------------+------+---------------+------+---------+------+------+-------------+
|    1 | SIMPLE      | employees_example | ALL  | NULL          | NULL | NULL    | NULL |    6 | Using where |
+------+-------------+-------------------+------+---------------+------+---------+------+------+-------------+

Here, the type is All, which means no index could be used. Looking at the rows count, a full table scan (all six rows) had to be performed in order to retrieve the record. If it's a requirement to search by phone number, an index will have to be created.

SHOW EXPLAIN example:

SHOW EXPLAIN FOR 1;
+------+-------------+-------+-------+---------------+------+---------+------+---------+-------------+
| id   | select_type | table | type  | possible_keys | key  | key_len | ref  | rows    | Extra       |
+------+-------------+-------+-------+---------------+------+---------+------+---------+-------------+
|    1 | SIMPLE      | tbl   | index | NULL          | a    | 5       | NULL | 1000107 | Using index |
+------+-------------+-------+-------+---------------+------+---------+------+---------+-------------+
1 row in set, 1 warning (0.00 sec)

Example of ref_or_null Optimization

SELECT * FROM table_name
  WHERE key_column=expr OR key_column IS NULL;

ref_or_null is something that often happens when you use subqueries with NOT IN as then one has to do an extra check for NULL values if the first value didn't have a matching row.

See Also

1.1.1.2.2.5 EXPLAIN ANALYZE

The syntax for the EXPLAIN ANALYZE feature was changed to ANALYZE statement, available since MariaDB 10.1.0. See ANALYZE statement.

1.1.1.2.2.6 EXPLAIN FORMAT=JSON

MariaDB starting with 10.1.2

Starting from version 10.1.2, MariaDB supports the EXPLAIN FORMAT=JSON syntax.

Contents

  1. Synopsis
  2. Output is different from MySQL
  3. Output format
  4. See also

Synopsis

EXPLAIN FORMAT=JSON is a variant of EXPLAIN command that produces output in JSON form. The output always has one row which has only one column titled "JSON". The contents are a JSON representation of the query plan, formatted for readability:

EXPLAIN FORMAT=JSON SELECT * FROM t1 WHERE col1=1\G

*************************** 1. row ***************************
EXPLAIN: {
  "query_block": {
    "select_id": 1,
    "table": {
      "table_name": "t1",
      "access_type": "ALL",
      "rows": 1000,
      "filtered": 100,
      "attached_condition": "(t1.col1 = 1)"
    }
  }
}

Output is different from MySQL

The output of MariaDB's EXPLAIN FORMAT=JSON is different from EXPLAIN FORMAT=JSON in MySQL.The reasons for that are:

  • MySQL's output has deficiencies. Some are listed here: EXPLAIN FORMAT=JSON in MySQL
  • The output of MySQL's EXPLAIN FORMAT=JSON is not defined. Even MySQL Workbench has trouble parsing it (see this blog post).
  • MariaDB has query optimizations that MySQL does not have. Ergo, MariaDB generates query plans that MySQL does not generate.

A (as yet incomplete) list of how MariaDB's output is different from MySQL can be found here: EXPLAIN FORMAT=JSON differences from MySQL.

Output format

TODO: MariaDB's output format description.

See also

  • ANALYZE FORMAT=JSON produces output like EXPLAIN FORMAT=JSON, but amended with the data from query execution.

1.1.1.2.2.7 SHOW EXPLAIN

Contents

  1. Syntax
  2. Description
    1. Possible Errors
    2. Differences Between SHOW EXPLAIN and EXPLAIN Outputs
      1. Background
      2. List of Recorded Differences
      3. Required Permissions
  3. See Also

Syntax

SHOW EXPLAIN FOR <thread_id>;

Description

The SHOW EXPLAIN command allows one to get an EXPLAIN (that is, a description of a query plan) of a query running in a certain thread.

SHOW EXPLAIN FOR <thread_id>;

will produce an EXPLAIN output for the query that thread number thread_id is running. The thread id can be obtained with SHOW PROCESSLIST.

SHOW EXPLAIN FOR 1;
+------+-------------+-------+-------+---------------+------+---------+------+---------+-------------+
| id   | select_type | table | type  | possible_keys | key  | key_len | ref  | rows    | Extra       |
+------+-------------+-------+-------+---------------+------+---------+------+---------+-------------+
|    1 | SIMPLE      | tbl   | index | NULL          | a    | 5       | NULL | 1000107 | Using index |
+------+-------------+-------+-------+---------------+------+---------+------+---------+-------------+
1 row in set, 1 warning (0.00 sec)

The output is always accompanied with a warning which shows the query the target thread is running (this shows what the EXPLAIN is for):

SHOW WARNINGS;
+-------+------+------------------------+
| Level | Code | Message                |
+-------+------+------------------------+
| Note  | 1003 | select sum(a) from tbl |
+-------+------+------------------------+
1 row in set (0.00 sec)

Possible Errors

The output can be only produced if the target thread is currently running a query, which has a ready query plan. If this is not the case, the output will be:

SHOW EXPLAIN FOR 2;
ERROR 1932 (HY000): Target is not running an EXPLAINable command

You will get this error when:

  • the target thread is not running a command for which one can run EXPLAIN
  • the target thread is running a command for which one can run EXPLAIN, but
    • there is no query plan yet (for example, tables are open and locks are acquired before the query plan is produced)

Differences Between SHOW EXPLAIN and EXPLAIN Outputs

Background

In MySQL, EXPLAIN execution takes a slightly different route from the way the real query (typically the SELECT) is optimized. This is unfortunate, and has caused a number of bugs in EXPLAIN. (For example, see MDEV-326, MDEV-410, and lp:1013343. lp:992942 is not directly about EXPLAIN, but it also would not have existed if MySQL didn't try to delete parts of a query plan in the middle of the query)

SHOW EXPLAIN examines a running SELECT, and hence its output may be slightly different from what EXPLAIN SELECT would produce. We did our best to make sure that either the difference is negligible, or SHOW EXPLAIN's output is closer to reality than EXPLAIN's output.

List of Recorded Differences

  • SHOW EXPLAIN may have Extra='no matching row in const table', where EXPLAIN would produce Extra='Impossible WHERE ...'
  • For queries with subqueries, SHOW EXPLAIN may print select_type==PRIMARY where regular EXPLAIN used to print select_type==SIMPLE, or vice versa.

Required Permissions

Running SHOW EXPLAIN requires the same permissions as running SHOW PROCESSLIST would.

See Also

1.1.1.2.2.8 Using Buffer UPDATE Algorithm

This article explains the UPDATE statement's Using Buffer algorithm.

Take the following table and query:

NameSalary
Babatunde1000
Jolana1050
Pankaja1300
UPDATE employees SET salary = salary+100 WHERE salary < 2000;

Suppose the employees table has an index on the salary column, and the optimizer decides to use a range scan on that index.

The optimizer starts a range scan on the salary index. We find the first record Babatunde, 1000. If we do an on-the-fly update, we immediately instruct the storage engine to change this record to be Babatunde, 1000+100=1100.

Then we proceed to search for the next record, and find Jolana, 1050. We instruct the storage engine to update it to be Jolana, 1050+100=1150.

Then we proceed to search for the next record ... and what happens next depends on the storage engine. In some storage engines, data changes are visible immediately, so we will find find the Babatunde, 1100 record that we wrote at the first step, modifying it again, giving Babatunde an undeserved raise. Then we will see Babatunde again and again, looping continually.

In order to prevent such situations, the optimizer checks whether the UPDATE statement is going to change key values for the keys it is using. In that case, it will use a different algorithm:

  1. Scan everyone with "salary<2000", remembering the rowids of the rows in a buffer.
  2. Read the buffer and apply the updates.

This way, each row will be updated only once.

The Using buffer EXPLAIN output indicates that the buffer as described above will be used.

1.1.1.2.3 BACKUP Commands

Commands used by backup tools

1.1.1.2.3.1 BACKUP STAGE

MariaDB starting with 10.4.1

The BACKUP STAGE commands were introduced in MariaDB 10.4.1.

Contents

  1. Syntax
  2. Goals with BACKUP STAGE Commands
  3. BACKUP STAGE Commands
    1. BACKUP STAGE START
    2. BACKUP STAGE FLUSH
    3. BACKUP STAGE BLOCK_DDL
    4. BACKUP STAGE BLOCK_COMMIT
    5. BACKUP STAGE END
  4. Using BACKUP STAGE Commands with Backup Tools
    1. Using BACKUP STAGE Commands with Mariabackup
    2. Using BACKUP STAGE Commands with Storage Snapshots
  5. Privileges
  6. Notes
  7. See Also

The BACKUP STAGE commands are a set of commands to make it possible to make an efficient external backup tool.

Syntax

BACKUP STAGE [START | FLUSH | BLOCK_DDL | BLOCK_COMMIT | END ]

In the following text, a transactional table means InnoDB or "InnoDB-like engine with redo log that can lock redo purges and can be copied without locks by an outside process".

Goals with BACKUP STAGE Commands

  • To be able to do a majority of the backup with the minimum possible server locks. Especially for transactional tables (InnoDB, MyRocks etc) there is only need for a very short block of new commits while copying statistics and log tables.
  • DDL are only needed to be blocked for a very short duration of the backup while mariabackup is copying the tables affected by DDL during the initial part of the backup.
  • Most non transactional tables (those that are not in use) will be copied during BACKUP STAGE START. The exceptions are system statistic and log tables that are not blocked during the backup until BLOCK_COMMIT.
  • Should work efficiently with backup tools that use disk snapshots.
  • Should work as efficiently as possible for all table types that store data on the local disks.
  • As little copying as possible under higher level stages/locks. For example, .frm (dictionary) and .trn (trigger) files should be copying while copying the table data.

BACKUP STAGE Commands

BACKUP STAGE START

The START stage is designed for the following tasks:

  • Blocks purge of redo files for storage engines that needs this (Aria)
  • Start logging of DDL commands into 'datadir'/ddl.log. This may take a short time as the command has to wait until there are no active DDL commands.

BACKUP STAGE FLUSH

The FLUSH stage is designed for the following tasks:

  • FLUSH all changes for inactive non-transactional tables, except for statistics and log tables.
  • Close all tables that are not in use, to ensure they are marked as closed for the backup.
  • BLOCK all new write locks for all non transactional tables (except statistics and log tables). The command will not wait for tables that are in use by read-only transactions.

DDLs don't have to be blocked at this stage as they can't cause the table to be in an inconsistent state. This is true also for non-transactional tables.

BACKUP STAGE BLOCK_DDL

The BLOCK_DDL stage is designed for the following tasks:

BACKUP STAGE BLOCK_COMMIT

The BLOCK_COMMIT stage is designed for the following tasks:

  • Lock the binary log and commit/rollback to ensure that no changes are committed to any tables. If there are active commits or data to be copied to the binary log this will be allowed to finish. Active transactions will not affect BLOCK_COMMIT.
  • This doesn't lock temporary tables that are not used by replication. However these will be blocked when it's time to write to the binary log.
  • Lock system log tables and statistics tables, flush them and mark them closed.

When the BLOCK_COMMIT's stages return, this is the 'backup time'. Everything committed will be in the backup and everything not committed will roll back.

Transactional engines will continue to do changes to the redo log during the BLOCK COMMIT stage, but this is not important as all of these will roll back later as the changes will not be committed.

BACKUP STAGE END

The END stage is designed for the following tasks:

  • End DDL logging
  • Free resources

Using BACKUP STAGE Commands with Backup Tools

Using BACKUP STAGE Commands with Mariabackup

The BACKUP STAGE commands are a set of commands to make it possible to make an efficient external backup tool. How Mariabackup uses these commands depends on whether you are using the version that is bundled with MariaDB Community Server or the version that is bundled with MariaDB Enterprise Server. See Mariabackup and BACKUP STAGE Commands for some examples on how Mariabackup uses these commands.

If you would like to use a version of Mariabackup that uses the BACKUP STAGE commands in an efficient way, then one option is to use MariaDB Enterprise Backup that is bundled with MariaDB Enterprise Server.

Using BACKUP STAGE Commands with Storage Snapshots

The BACKUP STAGE commands are a set of commands to make it possible to make an efficient external backup tool. These commands could even be used by tools that perform backups by taking a snapshot of a file system, SAN, or some other kind of storage device. See Storage Snapshots and BACKUP STAGE Commands for some examples on how to use each BACKUP STAGE command in an efficient way.

Privileges

BACKUP STAGE requires the RELOAD privilege.

Notes

  • Only one connection can run BACKUP STAGE START. If a second connection tries, it will wait until the first one has executed BACKUP STAGE END.
  • If the user skips a BACKUP STAGE, then all intermediate backup stages will automatically be run. This will allow us to add new stages within the BACKUP STAGE hierarchy in the future with even more precise locks without causing problems for tools using an earlier version of the BACKUP STAGE implementation.
  • One can use the max_statement_time or lock_wait_timeout system variables to ensure that a BACKUP STAGE command doesn't block the server too long.
  • DDL logging will only be available in MariaDB Enterprise Server 10.2 and later.

See Also

  • BACKUP LOCK Locking a table from DDL's.
  • MDEV-5336. Implement BACKUP STAGE for safe external backups.

1.1.1.2.3.2 BACKUP LOCK

MariaDB starting with 10.4.2

The BACKUP LOCK command was introduced in MariaDB 10.4.2.

Contents

  1. Syntax
  2. Usage in a Backup Tool
  3. Privileges
  4. Notes
  5. Implementation
  6. See Also

BACKUP LOCK blocks a table from DDL statements. This is mainly intended to be used by tools like mariabackup that need to ensure there are no DDLs on a table while the table files are opened. For example, for an Aria table that stores data in 3 files with extensions .frm, .MAI and .MAD. Normal read/write operations can continue as normal.

Syntax

To lock a table:

BACKUP LOCK table_name

To unlock a table:

BACKUP UNLOCK

Usage in a Backup Tool

BACKUP LOCK [database.]table_name;
 - Open all files related to a table (for example, t.frm, t.MAI and t.MYD)
BACKUP UNLOCK;
- Copy data
- Close files

This ensures that all files are from the same generation, that is created at the same time by the MariaDB server. This works, because the open files will point to the original table files which will not be affected if there is any ALTER TABLE while copying the files.

Privileges

BACKUP LOCK requires the RELOAD privilege.

Notes

  • The idea is that the BACKUP LOCK should be held for as short a time as possible by the backup tool. The time to take an uncontested lock is very short! One can easily do 50,000 locks/unlocks per second on low end hardware.
  • One should use different connections for BACKUP STAGE commands and BACKUP LOCK.

Implementation

  • Internally, BACKUP LOCK is implemented by taking an MDLSHARED_HIGH_PRIO MDL lock on the table object, which protects the table from any DDL operations.

See Also

1.1.1.2.3.3 Mariabackup and BACKUP STAGE Commands

1.1.1.2.3.4 Storage Snapshots and BACKUP STAGE Commands

MariaDB starting with 10.4.1

The BACKUP STAGE commands were introduced in MariaDB 10.4.1.

Contents

  1. Generic Backup Process with Storage Snapshots

The BACKUP STAGE commands are a set of commands to make it possible to make an efficient external backup tool. These commands could even be used by tools that perform backups by taking a snapshot of a file system, SAN, or some other kind of storage device.

Generic Backup Process with Storage Snapshots

A tool that backs up MariaDB by taking a snapshot of a file system, SAN, or some other kind of storage device could use each BACKUP STAGE command in the following way:

  • First, execute the following: 
BACKUP STAGE START
BACKUP STAGE BLOCK_COMMIT
  • Then, take the snapshot.
  • Then, execute the following: 
BACKUP STAGE END

The above ensures that all non-transactional tables are properly flushed to disk before the snapshot is done. Using BACKUP STAGE commands is also more efficient than using the FLUSH TABLES WITH READ LOCK command as the above set of commands will not block or be blocked by write operations to transactional tables.

Note that when the backup is completed, one should delete all files with the "#sql" prefix, as these are files used by concurrent running ALTER TABLE. Note that InnoDB will on server restart automatically delete any tables with the "#sql" prefix.

1.1.1.2.4 FLUSH Commands

Commands to reset (flush) various caches in MariaDB.

There are 2 related questions.

1.1.1.2.4.1 FLUSH

Syntax

FLUSH [NO_WRITE_TO_BINLOG | LOCAL]
    flush_option [, flush_option] ...

or when flushing tables:

FLUSH [NO_WRITE_TO_BINLOG | LOCAL] TABLES [table_list]  [table_flush_option]

Contents

  1. Syntax
  2. Description
  3. FLUSH RELAY LOGS
    1. Compatibility with MySQL
  4. FLUSH STATUS
    1. Global Status Variables that Support FLUSH STATUS
  5. The different usage of FLUSH TABLES
    1. The purpose of FLUSH TABLES
    2. The purpose of FLUSH TABLES WITH READ LOCK
    3. The purpose of FLUSH TABLES table_list
    4. The purpose of FLUSH TABLES table_list WITH READ LOCK
  6. Implementation of FLUSH TABLES commands in MariaDB 10.4.8 and above
    1. Implementation of FLUSH TABLES
    2. Implementation of FLUSH TABLES WITH READ LOCK
    3. Implementation of FLUSH TABLES table_list
    4. Implementation of FLUSH TABLES table_list FOR EXPORT
  7. FLUSH SSL
  8. Reducing Memory Usage

where table_list is a list of tables separated by , (comma).

Description

The FLUSH statement clears or reloads various internal caches used by MariaDB. To execute FLUSH, you must have the RELOAD privilege. See GRANT.

The RESET statement is similar to FLUSH. See RESET.

You cannot issue a FLUSH statement from within a stored function or a trigger. Doing so within a stored procedure is permitted, as long as it is not called by a stored function or trigger. See Stored Routine Limitations, Stored Function Limitations and Trigger Limitations.

If a listed table is a view, an error like the following will be produced:

ERROR 1347 (HY000): 'test.v' is not BASE TABLE

By default, FLUSH statements are written to the binary log and will be replicated. The NO_WRITE_TO_BINLOG keyword (LOCAL is an alias) will ensure the statement is not written to the binary log.

The different flush options are:

OptionDescription
CHANGED_PAGE_BITMAPSInternal command used for backup purposes. See the Information Schema CHANGED_PAGE_BITMAPS Table.
CLIENT_STATISTICSReset client statistics (see SHOW CLIENT_STATISTICS).
DES_KEY_FILEReloads the DES key file (Specified with the --des-key-file startup option).
HOSTSFlush the hostname cache (used for converting ip to host names and for unblocking blocked hosts. See max_connect_errors)
INDEX_STATISTICSReset index statistics (see SHOW INDEX_STATISTICS).
[ERROR | ENGINE | GENERAL | SLOW | BINARY | RELAY] LOGSClose and reopen the specified log type, or all log types if none are specified. FLUSH RELAY LOGS [connection-name] can be used to flush the relay logs for a specific connection. Only one connection can be specified per FLUSH command. See Multi-source replication. FLUSH ENGINE LOGS will delete all unneeded Aria redo logs. Since MariaDB 10.1.30 and MariaDB 10.2.11, FLUSH BINARY LOGS DELETE_DOMAIN_ID=(list-of-domains) can be used to discard obsolete GTID domains from the server's binary log state. In order for this to be successful, no event group from the listed GTID domains can be present in existing binary log files. If some still exist, then they must be purged prior to executing this command. If the command completes successfully, then it also rotates the binary log.
MASTERDeprecated option, use RESET MASTER instead.
PRIVILEGESReload all privileges from the privilege tables in the mysql database. If the server is started with --skip-grant-table option, this will activate the privilege tables again.
QUERY CACHEDefragment the query cache to better utilize its memory. If you want to reset the query cache, you can do it with RESET QUERY CACHE.
QUERY_RESPONSE_TIMESee the QUERY_RESPONSE_TIME plugin.
SLAVEDeprecated option, use RESET REPLICA or RESET SLAVE instead.
SSLUsed to dynamically reinitialize the server's TLS context by reloading the files defined by several TLS system variables. See FLUSH SSL for more information. This command was first added in MariaDB 10.4.1.
STATUSResets all server status variables that can be reset to 0. Not all global status variables support this, so not all global values are reset. See FLUSH STATUS for more information.
TABLEClose tables given as options or all open tables if no table list was used. From MariaDB 10.4.1, using without any table list will only close tables not in use, and tables not locked by the FLUSH TABLES connection. If there are no locked tables, FLUSH TABLES will be instant and will not cause any waits, as it no longer waits for tables in use. When a table list is provided, from MariaDB 10.4.1, the server will wait for the end of any transactions that are using the tables. Previously, FLUSH TABLES only waited for the statements to complete.
TABLESSame as FLUSH TABLE.
TABLES ... FOR EXPORTFor InnoDB tables, flushes table changes to disk to permit binary table copies while the server is running. See FLUSH TABLES ... FOR EXPORT for more.
TABLES WITH READ LOCKCloses all open tables. New tables are only allowed to be opened with read locks until an UNLOCK TABLES is given.
TABLES WITH READ LOCK AND DISABLE CHECKPOINTAs TABLES WITH READ LOCK but also disable all checkpoint writes by transactional table engines. This is useful when doing a disk snapshot of all tables.
TABLE_STATISTICSReset table statistics (see SHOW TABLE_STATISTICS).
USER_RESOURCESResets all per hour user resources. This enables clients that have exhausted their resources to connect again.
USER_STATISTICSReset user statistics (see SHOW USER_STATISTICS).

You can also use the mysqladmin client to flush things. Use mysqladmin --help to examine what flush commands it supports.

FLUSH RELAY LOGS

FLUSH RELAY LOGS 'connection_name';

Compatibility with MySQL

MariaDB starting with 10.7.0

The FOR CHANNEL keyword was added for MySQL compatibility. This is identical as using the channel_name directly after the FLUSH command.

For example, one can now use:

FLUSH RELAY LOGS FOR CHANNEL 'connection_name';

FLUSH STATUS

Server status variables can be reset by executing the following:

FLUSH STATUS;

Global Status Variables that Support FLUSH STATUS

Not all global status variables support being reset by FLUSH STATUS. Currently, the following status variables are reset by FLUSH STATUS:

The different usage of FLUSH TABLES

The purpose of FLUSH TABLES

The purpose of FLUSH TABLES is to clean up the open table cache and table definition cache from not in use tables. This frees up memory and file descriptors. Normally this is not needed as the caches works on a FIFO bases, but can be useful if the server seams to use up to much memory for some reason.

The purpose of FLUSH TABLES WITH READ LOCK

FLUSH TABLES WITH READ LOCK is useful if you want to take a backup of some tables. When FLUSH TABLES WITH READ LOCK returns, all write access to tables are blocked and all tables are marked as 'properly closed' on disk. The tables can still be used for read operations.

The purpose of FLUSH TABLES table_list

FLUSH TABLES table_list is useful if you want to copy a table object/files to or from the server. This command puts a lock that stops new users of the table and will wait until everyone has stopped using the table. The table is then removed from the table definition and table cache.

Note that it's up to the user to ensure that no one is accessing the table between FLUSH TABLES and the table is copied to or from the server. This can be secured by using LOCK TABLES.

If there are any tables locked by the connection that is using FLUSH TABLES all the locked tables will be closed as part of the flush and reopened and relocked before FLUSH TABLES returns. This allows one to copy the table after FLUSH TABLES returns without having any writes on the table. For now this works works with most tables, except InnoDB as InnoDB may do background purges on the table even while it's write locked.

The purpose of FLUSH TABLES table_list WITH READ LOCK

FLUSH TABLES table_list WITH READ LOCK should work as FLUSH TABLES WITH READ LOCK, but only those tables that are listed will be properly closed. However in practice this works exactly like FLUSH TABLES WITH READ LOCK as the FLUSH command has anyway to wait for all WRITE operations to end because we are depending on a global read lock for this code. In the future we should consider fixing this to instead use meta data locks.

Implementation of FLUSH TABLES commands in MariaDB 10.4.8 and above

Implementation of FLUSH TABLES

  • Free memory and file descriptors not in use

Implementation of FLUSH TABLES WITH READ LOCK

  • Lock all tables read only for simple old style backup.
  • All background writes are suspended and tables are marked as closed.
  • No statement requiring table changes are allowed for any user until UNLOCK TABLES.

Instead of using FLUSH TABLE WITH READ LOCK one should in most cases instead use BACKUP STAGE BLOCK_COMMIT.

Implementation of FLUSH TABLES table_list

  • Free memory and file descriptors for tables not in use from table list.
  • Lock given tables as read only.
  • Wait until all translations has ended that uses any of the given tables.
  • Wait until all background writes are suspended and tables are marked as closed.

Implementation of FLUSH TABLES table_list FOR EXPORT

  • Free memory and file descriptors for tables not in use from table list
  • Lock given tables as read.
  • Wait until all background writes are suspended and tables are marked as closed.
  • Check that all tables supports FOR EXPORT
  • No changes to these tables allowed until UNLOCK TABLES

This is basically the same behavior as in old MariaDB version if one first lock the tables, then do FLUSH TABLES. The tables will be copyable until UNLOCK TABLES.

FLUSH SSL

MariaDB starting with 10.4

The FLUSH SSL command was first added in MariaDB 10.4.

In MariaDB 10.4 and later, the FLUSH SSL command can be used to dynamically reinitialize the server's TLS context. This is most useful if you need to replace a certificate that is about to expire without restarting the server.

This operation is performed by reloading the files defined by the following TLS system variables:

These TLS system variables are not dynamic, so their values can not be changed without restarting the server.

If you want to dynamically reinitialize the server's TLS context, then you need to change the certificate and key files at the relevant paths defined by these TLS system variables, without actually changing the values of the variables. See MDEV-19341 for more information.

Reducing Memory Usage

To flush some of the global caches that take up memory, you could execute the following command:

FLUSH LOCAL HOSTS,
   QUERY CACHE, 
   TABLE_STATISTICS, 
   INDEX_STATISTICS, 
   USER_STATISTICS;

1.1.1.2.4.2 FLUSH QUERY CACHE

Description

You can defragment the query cache to better utilize its memory with the FLUSH QUERY CACHE statement. The statement does not remove any queries from the cache.

The RESET QUERY CACHE statement removes all query results from the query cache. The FLUSH TABLES statement also does this.

1.1.1.2.4.3 FLUSH TABLES FOR EXPORT

Syntax

FLUSH TABLES table_name [, table_name] FOR EXPORT

Contents

  1. Syntax
  2. Description
  3. Example
  4. See Also

Description

FLUSH TABLES ... FOR EXPORT flushes changes to the specified tables to disk so that binary copies can be made while the server is still running. This works for Archive, Aria, CSV, InnoDB, MyISAM, MERGE, and XtraDB tables.

The table is read locked until one has issued UNLOCK TABLES.

If a storage engine does not support FLUSH TABLES FOR EXPORT, a 1031 error (SQLSTATE 'HY000') is produced.

If FLUSH TABLES ... FOR EXPORT is in effect in the session, the following statements will produce an error if attempted:

  • FLUSH TABLES WITH READ LOCK
  • FLUSH TABLES ... WITH READ LOCK
  • FLUSH TABLES ... FOR EXPORT
  • Any statement trying to update any table

If any of the following statements is in effect in the session, attempting FLUSH TABLES ... FOR EXPORT will produce an error.

  • FLUSH TABLES ... WITH READ LOCK
  • FLUSH TABLES ... FOR EXPORT
  • LOCK TABLES ... READ
  • LOCK TABLES ... WRITE

FLUSH FOR EXPORT is not written to the binary log.

This statement requires the RELOAD and the LOCK TABLES privileges.

If one of the specified tables cannot be locked, none of the tables will be locked.

If a table does not exist, an error like the following will be produced:

ERROR 1146 (42S02): Table 'test.xxx' doesn't exist

If a table is a view, an error like the following will be produced:

ERROR 1347 (HY000): 'test.v' is not BASE TABLE

Example

FLUSH TABLES test.t1 FOR EXPORT;
#  Copy files related to the table (see below)
UNLOCK TABLES;

For a full description, please see copying MariaDB tables.

See Also

1.1.1.2.5 Replication Commands

The terms master and slave have historically been used in replication, but the terms terms primary and replica are now preferred. The old terms are used still used in parts of the documentation, and in MariaDB commands, although MariaDB 10.5 has begun the process of renaming. The documentation process is ongoing. See MDEV-18777 to follow progress on this effort.

A list of replication-related commands. See replication for more replication-related information.

1.1.1.2.5.1 CHANGE MASTER TO

The terms master and slave have historically been used in replication, but the terms terms primary and replica are now preferred. The old terms are used still used in parts of the documentation, and in MariaDB commands, although MariaDB 10.5 has begun the process of renaming. The documentation process is ongoing. See MDEV-18777 to follow progress on this effort.

Syntax

CHANGE MASTER ['connection_name'] TO master_def [, master_def] ... [FOR CHANNEL 'channel_name']

master_def:
    MASTER_BIND = 'interface_name'
  | MASTER_HOST = 'host_name'
  | MASTER_USER = 'user_name'
  | MASTER_PASSWORD = 'password'
  | MASTER_PORT = port_num
  | MASTER_CONNECT_RETRY = interval
  | MASTER_HEARTBEAT_PERIOD = interval
  | MASTER_LOG_FILE = 'master_log_name'
  | MASTER_LOG_POS = master_log_pos
  | RELAY_LOG_FILE = 'relay_log_name'
  | RELAY_LOG_POS = relay_log_pos
  | MASTER_DELAY = interval
  | MASTER_SSL = {0|1}
  | MASTER_SSL_CA = 'ca_file_name'
  | MASTER_SSL_CAPATH = 'ca_directory_name'
  | MASTER_SSL_CERT = 'cert_file_name'
  | MASTER_SSL_CRL = 'crl_file_name'
  | MASTER_SSL_CRLPATH = 'crl_directory_name'
  | MASTER_SSL_KEY = 'key_file_name'
  | MASTER_SSL_CIPHER = 'cipher_list'
  | MASTER_SSL_VERIFY_SERVER_CERT = {0|1}
  | MASTER_USE_GTID = {current_pos|slave_pos|no}
  | IGNORE_SERVER_IDS = (server_id_list)
  | DO_DOMAIN_IDS = ([N,..])
  | IGNORE_DOMAIN_IDS = ([N,..])

Contents

  1. Syntax
  2. Description
  3. Multi-Source Replication
    1. default_master_connection
    2. connection_name
  4. Options
    1. Connection Options
      1. MASTER_USER
      2. MASTER_PASSWORD
      3. MASTER_HOST
      4. MASTER_PORT
      5. MASTER_CONNECT_RETRY
      6. MASTER_BIND
      7. MASTER_HEARTBEAT_PERIOD
    2. TLS Options
      1. MASTER_SSL
      2. MASTER_SSL_CA
      3. MASTER_SSL_CAPATH
      4. MASTER_SSL_CERT
      5. MASTER_SSL_CRL
      6. MASTER_SSL_CRLPATH
      7. MASTER_SSL_KEY
      8. MASTER_SSL_CIPHER
      9. MASTER_SSL_VERIFY_SERVER_CERT
    3. Binary Log Options
      1. MASTER_LOG_FILE
      2. MASTER_LOG_POS
    4. Relay Log Options
      1. RELAY_LOG_FILE
      2. RELAY_LOG_POS
    5. GTID Options
      1. MASTER_USE_GTID
    6. Replication Filter Options
      1. IGNORE_SERVER_IDS
      2. DO_DOMAIN_IDS
      3. IGNORE_DOMAIN_IDS
    7. Delayed Replication Options
      1. MASTER_DELAY
  5. Changing Option Values
  6. Option Persistence
  7. GTID Persistence
  8. Creating a Slave from a Backup
  9. Example
  10. See Also

Description

The CHANGE MASTER statement sets the options that a replica uses to connect to and replicate from a primary.

MariaDB starting with 10.7.0

The FOR CHANNEL keyword was added for MySQL compatibility. This is identical to using the channel_name directly after CHANGE MASTER.

Multi-Source Replication

If you are using multi-source replication, then you need to specify a connection name when you execute CHANGE MASTER. There are two ways to do this:

  • Setting the default_master_connection system variable prior to executing CHANGE MASTER.
  • Setting the connection_name parameter when executing CHANGE MASTER.

default_master_connection

SET default_master_connection = 'gandalf';
STOP SLAVE;
CHANGE MASTER TO 
   MASTER_PASSWORD='new3cret';
START SLAVE;

connection_name

STOP SLAVE 'gandalf';
CHANGE MASTER 'gandalf' TO 
   MASTER_PASSWORD='new3cret';
START SLAVE 'gandalf';

Options

Connection Options

MASTER_USER

The MASTER_USER option for CHANGE MASTER defines the user account that the replica will use to connect to the primary.

This user account will need the REPLICATION SLAVE privilege (or, from MariaDB 10.5.1, the REPLICATION REPLICA on the primary.

For example:

STOP SLAVE;
CHANGE MASTER TO
   MASTER_USER='repl',
   MASTER_PASSWORD='new3cret';
START SLAVE;

The maximum length of the MASTER_USER string is 96 characters until MariaDB 10.5, and 128 characters from MariaDB 10.6.

MASTER_PASSWORD

The MASTER_USER option for CHANGE MASTER defines the password that the replica will use to connect to the primary as the user account defined by the MASTER_USER option.

For example:

STOP SLAVE;
CHANGE MASTER TO 
   MASTER_PASSWORD='new3cret';
START SLAVE;

The maximum length of the MASTER_PASSWORD string is 32 characters.

MASTER_HOST

The MASTER_HOST option for CHANGE MASTER defines the hostname or IP address of the primary.

If you set the value of the MASTER_HOST option to the empty string, then that is not the same as not setting the option's value at all. If you set the value of the MASTER_HOST option to the empty string, then the CHANGE MASTER command will fail with an error. In MariaDB 5.3 and before, if you set the value of the MASTER_HOST option to the empty string, then the CHANGE MASTER command would succeed, but the subsequent START SLAVE command would fail.

For example:

STOP SLAVE;
CHANGE MASTER TO
   MASTER_HOST='dbserver1.example.com',
   MASTER_USER='repl',
   MASTER_PASSWORD='new3cret',
   MASTER_USE_GTID=slave_pos;
START SLAVE;

If you set the value of the MASTER_HOST option in a CHANGE MASTER command, then the replica assumes that the primary is different from before, even if you set the value of this option to the same value it had previously. In this scenario, the replica will consider the old values for the primary's binary log file name and position to be invalid for the new primary. As a side effect, if you do not explicitly set the values of the MASTER_LOG_FILE and MASTER_LOG_POS options in the statement, then the statement will be implicitly appended with MASTER_LOG_FILE='' and MASTER_LOG_POS=4. However, if you enable GTID mode for replication by setting the MASTER_USE_GTID option to some value other than no in the statement, then these values will effectively be ignored anyway.

Replicas cannot connect to primaries using Unix socket files or Windows named pipes. The replica must connect to the primary using TCP/IP.

The maximum length of the MASTER_HOST string is 60 characters until MariaDB 10.5, and 255 characters from MariaDB 10.6.

MASTER_PORT

The MASTER_PORT option for CHANGE MASTER defines the TCP/IP port of the primary.

For example:

STOP SLAVE;
CHANGE MASTER TO
   MASTER_HOST='dbserver1.example.com',
   MASTER_PORT=3307,
   MASTER_USER='repl',
   MASTER_PASSWORD='new3cret',
   MASTER_USE_GTID=slave_pos;
START SLAVE;

If you set the value of the MASTER_PORT option in a CHANGE MASTER command, then the replica assumes that the primary is different from before, even if you set the value of this option to the same value it had previously. In this scenario, the replica will consider the old values for the primary's binary log file name and position to be invalid for the new primary. As a side effect, if you do not explicitly set the values of the MASTER_LOG_FILE and MASTER_LOG_POS options in the statement, then the statement will be implicitly appended with MASTER_LOG_FILE='' and MASTER_LOG_POS=4. However, if you enable GTID mode for replication by setting the MASTER_USE_GTID option to some value other than no in the statement, then these values will effectively be ignored anyway.

Replicas cannot connect to primaries using Unix socket files or Windows named pipes. The replica must connect to the primary using TCP/IP.

MASTER_CONNECT_RETRY

The MASTER_CONNECT_RETRY option for CHANGE MASTER defines how many seconds that the replica will wait between connection retries. The default is 60.

STOP SLAVE;
CHANGE MASTER TO 
   MASTER_CONNECT_RETRY=20;
START SLAVE;

The number of connection attempts is limited by the master_retry_count option. It can be set either on the command-line or in a server option group in an option file prior to starting up the server. For example:

[mariadb]
...
master_retry_count=4294967295

MASTER_BIND

The MASTER_BIND option for CHANGE MASTER is only supported by MySQL 5.6.2 and later and by MySQL NDB Cluster 7.3.1 and later. This option is not supported by MariaDB. See MDEV-19248 for more information.

The MASTER_BIND option for CHANGE MASTER can be used on replicas that have multiple network interfaces to choose which network interface the replica will use to connect to the primary.

MASTER_HEARTBEAT_PERIOD

The MASTER_HEARTBEAT_PERIOD option for CHANGE MASTER can be used to set the interval in seconds between replication heartbeats. Whenever the primary's binary log is updated with an event, the waiting period for the next heartbeat is reset.

This option's interval argument has the following characteristics:

  • It is a decimal value with a range of 0 to 4294967 seconds.
  • It has a resolution of hundredths of a second.
  • Its smallest valid non-zero value is 0.001.
  • Its default value is the value of the slave_net_timeout system variable divided by 2.
  • If it's set to 0, then heartbeats are disabled.

Heartbeats are sent by the primary only if there are no unsent events in the binary log file for a period longer than the interval.

If the RESET SLAVE statement is executed, then the heartbeat interval is reset to the default.

If the slave_net_timeout system variable is set to a value that is lower than the current heartbeat interval, then a warning will be issued.

TLS Options

The TLS options are used for providing information about TLS. The options can be set even on replicas that are compiled without TLS support. The TLS options are saved to either the default master.info file or the file that is configured by the master_info_file option, but these TLS options are ignored unless the replica supports TLS.

See Replication with Secure Connections for more information.

MASTER_SSL

The MASTER_SSL option for CHANGE MASTER tells the replica whether to force TLS for the connection. The valid values are 0 or 1.

For example:

STOP SLAVE;
CHANGE MASTER TO
   MASTER_SSL=1;
START SLAVE;

MASTER_SSL_CA

The MASTER_SSL_CA option for CHANGE MASTER defines a path to a PEM file that should contain one or more X509 certificates for trusted Certificate Authorities (CAs) to use for TLS. This option requires that you use the absolute path, not a relative path. This option implies the MASTER_SSL option.

For example:

STOP SLAVE;
CHANGE MASTER TO
   MASTER_SSL_CERT='/etc/my.cnf.d/certificates/server-cert.pem',
   MASTER_SSL_KEY='/etc/my.cnf.d/certificates/server-key.pem',
   MASTER_SSL_CA='/etc/my.cnf.d/certificates/ca.pem',
   MASTER_SSL_VERIFY_SERVER_CERT=1;
START SLAVE;

See Secure Connections Overview: Certificate Authorities (CAs) for more information.

The maximum length of MASTER_SSL_CA string is 511 characters.

MASTER_SSL_CAPATH

The MASTER_SSL_CAPATH option for CHANGE MASTER defines a path to a directory that contains one or more PEM files that should each contain one X509 certificate for a trusted Certificate Authority (CA) to use for TLS. This option requires that you use the absolute path, not a relative path. The directory specified by this option needs to be run through the openssl rehash command. This option implies the MASTER_SSL option.

For example:

STOP SLAVE;
CHANGE MASTER TO
   MASTER_SSL_CERT='/etc/my.cnf.d/certificates/server-cert.pem',
   MASTER_SSL_KEY='/etc/my.cnf.d/certificates/server-key.pem',
   MASTER_SSL_CAPATH='/etc/my.cnf.d/certificates/ca/',
   MASTER_SSL_VERIFY_SERVER_CERT=1;
START SLAVE;

See Secure Connections Overview: Certificate Authorities (CAs) for more information.

The maximum length of MASTER_SSL_CA_PATH string is 511 characters.

MASTER_SSL_CERT

The MASTER_SSL_CERT option for CHANGE MASTER defines a path to the X509 certificate file to use for TLS. This option requires that you use the absolute path, not a relative path. This option implies the MASTER_SSL option.

For example:

STOP SLAVE;
CHANGE MASTER TO
   MASTER_SSL_CERT='/etc/my.cnf.d/certificates/server-cert.pem',
   MASTER_SSL_KEY='/etc/my.cnf.d/certificates/server-key.pem',
   MASTER_SSL_CA='/etc/my.cnf.d/certificates/ca.pem',
   MASTER_SSL_VERIFY_SERVER_CERT=1;
START SLAVE;

The maximum length of MASTER_SSL_CERT string is 511 characters.

MASTER_SSL_CRL

The MASTER_SSL_CRL option for CHANGE MASTER defines a path to a PEM file that should contain one or more revoked X509 certificates to use for TLS. This option requires that you use the absolute path, not a relative path.

This option is only supported if the server was built with OpenSSL. If the server was built with yaSSL, then this option is not supported. See TLS and Cryptography Libraries Used by MariaDB for more information about which libraries are used on which platforms.

For example:

STOP SLAVE;
CHANGE MASTER TO
   MASTER_SSL_CERT='/etc/my.cnf.d/certificates/server-cert.pem',
   MASTER_SSL_KEY='/etc/my.cnf.d/certificates/server-key.pem',
   MASTER_SSL_CA='/etc/my.cnf.d/certificates/ca.pem',
   MASTER_SSL_VERIFY_SERVER_CERT=1,
   MASTER_SSL_CRL='/etc/my.cnf.d/certificates/crl.pem';
START SLAVE;

See Secure Connections Overview: Certificate Revocation Lists (CRLs) for more information.

The maximum length of MASTER_SSL_CRL string is 511 characters.

MASTER_SSL_CRLPATH

The MASTER_SSL_CRLPATH option for CHANGE MASTER defines a path to a directory that contains one or more PEM files that should each contain one revoked X509 certificate to use for TLS. This option requires that you use the absolute path, not a relative path. The directory specified by this variable needs to be run through the openssl rehash command.

This option is only supported if the server was built with OpenSSL. If the server was built with yaSSL, then this option is not supported. See TLS and Cryptography Libraries Used by MariaDB for more information about which libraries are used on which platforms.

For example:

STOP SLAVE;
CHANGE MASTER TO
   MASTER_SSL_CERT='/etc/my.cnf.d/certificates/server-cert.pem',
   MASTER_SSL_KEY='/etc/my.cnf.d/certificates/server-key.pem',
   MASTER_SSL_CA='/etc/my.cnf.d/certificates/ca.pem',
   MASTER_SSL_VERIFY_SERVER_CERT=1,
   MASTER_SSL_CRLPATH='/etc/my.cnf.d/certificates/crl/';
START SLAVE;

See Secure Connections Overview: Certificate Revocation Lists (CRLs) for more information.

The maximum length of MASTER_SSL_CRL_PATH string is 511 characters.

MASTER_SSL_KEY

The MASTER_SSL_KEY option for CHANGE MASTER defines a path to a private key file to use for TLS. This option requires that you use the absolute path, not a relative path. This option implies the MASTER_SSL option.

For example:

STOP SLAVE;
CHANGE MASTER TO
   MASTER_SSL_CERT='/etc/my.cnf.d/certificates/server-cert.pem',
   MASTER_SSL_KEY='/etc/my.cnf.d/certificates/server-key.pem',
   MASTER_SSL_CA='/etc/my.cnf.d/certificates/ca.pem',
   MASTER_SSL_VERIFY_SERVER_CERT=1;
START SLAVE;

The maximum length of MASTER_SSL_KEY string is 511 characters.

MASTER_SSL_CIPHER

The MASTER_SSL_CIPHER option for CHANGE MASTER defines the list of permitted ciphers or cipher suites to use for TLS. Besides cipher names, if MariaDB was compiled with OpenSSL, this option could be set to "SSLv3" or "TLSv1.2" to allow all SSLv3 or all TLSv1.2 ciphers. Note that the TLSv1.3 ciphers cannot be excluded when using OpenSSL, even by using this option. See Using TLSv1.3 for details. This option implies the MASTER_SSL option.

For example:

STOP SLAVE;
CHANGE MASTER TO
   MASTER_SSL_CERT='/etc/my.cnf.d/certificates/server-cert.pem',
   MASTER_SSL_KEY='/etc/my.cnf.d/certificates/server-key.pem',
   MASTER_SSL_CA='/etc/my.cnf.d/certificates/ca.pem',
   MASTER_SSL_VERIFY_SERVER_CERT=1,
   MASTER_SSL_CIPHER='TLSv1.2';
START SLAVE;

The maximum length of MASTER_SSL_CIPHER string is 511 characters.

MASTER_SSL_VERIFY_SERVER_CERT

The MASTER_SSL_VERIFY_SERVER_CERT option for CHANGE MASTER enables server certificate verification. This option is disabled by default.

For example:

STOP SLAVE;
CHANGE MASTER TO
   MASTER_SSL_CERT='/etc/my.cnf.d/certificates/server-cert.pem',
   MASTER_SSL_KEY='/etc/my.cnf.d/certificates/server-key.pem',
   MASTER_SSL_CA='/etc/my.cnf.d/certificates/ca.pem',
   MASTER_SSL_VERIFY_SERVER_CERT=1;
START SLAVE;

See Secure Connections Overview: Server Certificate Verification for more information.

Binary Log Options

These options are related to the binary log position on the primary.

MASTER_LOG_FILE

The MASTER_LOG_FILE option for CHANGE MASTER can be used along with MASTER_LOG_POS to specify the coordinates at which the replica's I/O thread should begin reading from the primary's binary logs the next time the thread starts.

For example:

STOP SLAVE;
CHANGE MASTER TO
   MASTER_LOG_FILE='master2-bin.001',
   MASTER_LOG_POS=4;
START SLAVE;

The MASTER_LOG_FILE and MASTER_LOG_POS options cannot be specified if the RELAY_LOG_FILE and RELAY_LOG_POS options were also specified.

The MASTER_LOG_FILE and MASTER_LOG_POS options are effectively ignored if you enable GTID mode for replication by setting the MASTER_USE_GTID option to some value other than no in the statement.

MASTER_LOG_POS

The MASTER_LOG_POS option for CHANGE MASTER can be used along with MASTER_LOG_FILE to specify the coordinates at which the replica's I/O thread should begin reading from the primary's binary logs the next time the thread starts.

For example:

STOP SLAVE;
CHANGE MASTER TO
   MASTER_LOG_FILE='master2-bin.001',
   MASTER_LOG_POS=4;
START SLAVE;

The MASTER_LOG_FILE and MASTER_LOG_POS options cannot be specified if the RELAY_LOG_FILE and RELAY_LOG_POS options were also specified.

The MASTER_LOG_FILE and MASTER_LOG_POS options are effectively ignored if you enable GTID mode for replication by setting the MASTER_USE_GTID option to some value other than no in the statement.

Relay Log Options

These options are related to the relay log position on the replica.

RELAY_LOG_FILE

The RELAY_LOG_FILE option for CHANGE MASTER can be used along with the RELAY_LOG_POS option to specify the coordinates at which the replica's SQL thread should begin reading from the relay log the next time the thread starts.

The CHANGE MASTER statement usually deletes all relay log files. However, if the RELAY_LOG_FILE and/or RELAY_LOG_POS options are specified, then existing relay log files are kept.

When you want to change the relay log position, you only need to stop the replica's SQL thread. The replica's I/O thread can continue running. The STOP SLAVE and START SLAVE statements support the SQL_THREAD option for this scenario. For example:

STOP SLAVE SQL_THREAD;
CHANGE MASTER TO
   RELAY_LOG_FILE='slave-relay-bin.006',
   RELAY_LOG_POS=4025;
START SLAVE SQL_THREAD;

When the value of this option is changed, the metadata about the replica's SQL thread's position in the relay logs will also be changed in the relay-log.info file or the file that is configured by the relay_log_info_file system variable.

The RELAY_LOG_FILE and RELAY_LOG_POS options cannot be specified if the MASTER_LOG_FILE and MASTER_LOG_POS options were also specified.

RELAY_LOG_POS

The RELAY_LOG_POS option for CHANGE MASTER can be used along with the RELAY_LOG_FILE option to specify the coordinates at which the replica's SQL thread should begin reading from the relay log the next time the thread starts.

The CHANGE MASTER statement usually deletes all relay log files. However, if the RELAY_LOG_FILE and/or RELAY_LOG_POS options are specified, then existing relay log files are kept.

When you want to change the relay log position, you only need to stop the replica's SQL thread. The replica's I/O thread can continue running. The STOP SLAVE and START SLAVE statements support the SQL_THREAD option for this scenario. For example:

STOP SLAVE SQL_THREAD;
CHANGE MASTER TO
   RELAY_LOG_FILE='slave-relay-bin.006',
   RELAY_LOG_POS=4025;
START SLAVE SQL_THREAD;

When the value of this option is changed, the metadata about the replica's SQL thread's position in the relay logs will also be changed in the relay-log.info file or the file that is configured by the relay_log_info_file system variable.

The RELAY_LOG_FILE and RELAY_LOG_POS options cannot be specified if the MASTER_LOG_FILE and MASTER_LOG_POS options were also specified.

GTID Options

MASTER_USE_GTID

The MASTER_USE_GTID option for CHANGE MASTER can be used to configure the replica to use the global transaction ID (GTID) when connecting to a primary. The possible values are:

  • current_pos - Replicate in GTID mode and use gtid_current_pos as the position to start downloading transactions from the primary.
  • slave_pos - Replicate in GTID mode and use gtid_slave_pos as the position to start downloading transactions from the primary. From MariaDB 10.5.1, replica_pos is an alias for slave_pos.
  • no - Don't replicate in GTID mode.

For example:

STOP SLAVE;
CHANGE MASTER TO
   MASTER_USE_GTID = current_pos;
START SLAVE;

Or:

STOP SLAVE;
SET GLOBAL gtid_slave_pos='0-1-153';
CHANGE MASTER TO
   MASTER_USE_GTID = slave_pos;
START SLAVE;

Replication Filter Options

Also see Replication filters.

IGNORE_SERVER_IDS

The IGNORE_SERVER_IDS option for CHANGE MASTER can be used to configure a replica to ignore binary log events that originated from certain servers. Filtered binary log events will not get logged to the replica’s relay log, and they will not be applied by the replica.

The option's value can be specified by providing a comma-separated list of server_id values. For example:

STOP SLAVE;
CHANGE MASTER TO 
   IGNORE_SERVER_IDS = (3,5);
START SLAVE;

If you would like to clear a previously set list, then you can set the value to an empty list. For example:

STOP SLAVE;
CHANGE MASTER TO 
   IGNORE_SERVER_IDS = ();
START SLAVE;

DO_DOMAIN_IDS

MariaDB starting with 10.1.2

The DO_DOMAIN_IDS option for CHANGE MASTER was first added in MariaDB 10.1.2.

The DO_DOMAIN_IDS option for CHANGE MASTER can be used to configure a replica to only apply binary log events if the transaction's GTID is in a specific gtid_domain_id value. Filtered binary log events will not get logged to the replica’s relay log, and they will not be applied by the replica.

The option's value can be specified by providing a comma-separated list of gtid_domain_id values. Duplicate values are automatically ignored. For example:

STOP SLAVE;
CHANGE MASTER TO 
   DO_DOMAIN_IDS = (1,2);
START SLAVE;

If you would like to clear a previously set list, then you can set the value to an empty list. For example:

STOP SLAVE;
CHANGE MASTER TO 
   DO_DOMAIN_IDS = ();
START SLAVE;

The DO_DOMAIN_IDS option and the IGNORE_DOMAIN_IDS option cannot both be set to non-empty values at the same time. If you want to set the DO_DOMAIN_IDS option, and the IGNORE_DOMAIN_IDS option was previously set, then you need to clear the value of the IGNORE_DOMAIN_IDS option. For example:

STOP SLAVE;
CHANGE MASTER TO 
   IGNORE_DOMAIN_IDS = (), 
   DO_DOMAIN_IDS = (1,2);
START SLAVE;

The DO_DOMAIN_IDS option can only be specified if the replica is replicating in GTID mode. Therefore, the MASTER_USE_GTID option must also be set to some value other than no in order to use this option.

IGNORE_DOMAIN_IDS

MariaDB starting with 10.1.2

The IGNORE_DOMAIN_IDS option for CHANGE MASTER was first added in MariaDB 10.1.2.

The IGNORE_DOMAIN_IDS option for CHANGE MASTER can be used to configure a replica to ignore binary log events if the transaction's GTID is in a specific gtid_domain_id value. Filtered binary log events will not get logged to the replica’s relay log, and they will not be applied by the replica.

The option's value can be specified by providing a comma-separated list of gtid_domain_id values. Duplicate values are automatically ignored. For example:

STOP SLAVE;
CHANGE MASTER TO 
   IGNORE_DOMAIN_IDS = (1,2);
START SLAVE;

If you would like to clear a previously set list, then you can set the value to an empty list. For example:

STOP SLAVE;
CHANGE MASTER TO 
   IGNORE_DOMAIN_IDS = ();
START SLAVE;

The DO_DOMAIN_IDS option and the IGNORE_DOMAIN_IDS option cannot both be set to non-empty values at the same time. If you want to set the IGNORE_DOMAIN_IDS option, and the DO_DOMAIN_IDS option was previously set, then you need to clear the value of the DO_DOMAIN_IDS option. For example:

STOP SLAVE;
CHANGE MASTER TO 
   DO_DOMAIN_IDS = (), 
   IGNORE_DOMAIN_IDS = (1,2);
START SLAVE;

The IGNORE_DOMAIN_IDS option can only be specified if the replica is replicating in GTID mode. Therefore, the MASTER_USE_GTID option must also be set to some value other than no in order to use this option.

Delayed Replication Options

MASTER_DELAY

MariaDB starting with 10.2.3

The MASTER_DELAY option for CHANGE MASTER was first added in MariaDB 10.2.3 to enable delayed replication.

The MASTER_DELAY option for CHANGE MASTER can be used to enable delayed replication. This option specifies the time in seconds (at least) that a replica should lag behind the primary up to a maximum value of 2147483647, or about 68 years. Before executing an event, the replica will first wait, if necessary, until the given time has passed since the event was created on the primary. The result is that the replica will reflect the state of the primary some time back in the past. The default is zero, no delay.

STOP SLAVE;
CHANGE MASTER TO 
   MASTER_DELAY=3600;
START SLAVE;

Changing Option Values

If you don't specify a given option when executing the CHANGE MASTER statement, then the option keeps its old value in most cases. Most of the time, there is no need to specify the options that do not need to change. For example, if the password for the user account that the replica uses to connect to its primary has changed, but no other options need to change, then you can just change the MASTER_PASSWORD option by executing the following commands:

STOP SLAVE;
CHANGE MASTER TO 
   MASTER_PASSWORD='new3cret';
START SLAVE;

There are some cases where options are implicitly reset, such as when the MASTER_HOST and MASTER_PORT options are changed.

Option Persistence

The values of the MASTER_LOG_FILE and MASTER_LOG_POS options (i.e. the binary log position on the primary) and most other options are written to either the default master.info file or the file that is configured by the master_info_file option. The replica's I/O thread keeps this binary log position updated as it downloads events only when MASTER_USE_GTID option is set to NO. Otherwise the file is not updated on a per event basis.

The master_info_file option can be set either on the command-line or in a server option group in an option file prior to starting up the server. For example:

[mariadb]
...
master_info_file=/mariadb/myserver1-master.info

The values of the RELAY_LOG_FILE and RELAY_LOG_POS options (i.e. the relay log position) are written to either the default relay-log.info file or the file that is configured by the relay_log_info_file system variable. The replica's SQL thread keeps this relay log position updated as it applies events.

The relay_log_info_file system variable can be set either on the command-line or in a server option group in an option file prior to starting up the server. For example:

[mariadb]
...
relay_log_info_file=/mariadb/myserver1-relay-log.info

GTID Persistence

If the replica is replicating binary log events that contain GTIDs, then the replica's SQL thread will write every GTID that it applies to the mysql.gtid_slave_pos table. This GTID can be inspected and modified through the gtid_slave_pos system variable.

If the replica has the log_slave_updates system variable enabled and if the replica has the binary log enabled, then every write by the replica's SQL thread will also go into the replica's binary log. This means that GTIDs of replicated transactions would be reflected in the value of the gtid_binlog_pos system variable.

Creating a Slave from a Backup

The CHANGE MASTER statement is useful for setting up a replica when you have a backup of the primary and you also have the binary log position or GTID position corresponding to the backup.

After restoring the backup on the replica, you could execute something like this to use the binary log position:

CHANGE MASTER TO
   MASTER_LOG_FILE='master2-bin.001',
   MASTER_LOG_POS=4;
START SLAVE;

Or you could execute something like this to use the GTID position:

SET GLOBAL gtid_slave_pos='0-1-153';
CHANGE MASTER TO
   MASTER_USE_GTID=slave_pos;
START SLAVE;

See Setting up a Replication Slave with Mariabackup for more information on how to do this with Mariabackup.

Example

The following example changes the primary and primary's binary log coordinates. This is used when you want to set up the replica to replicate the primary:

CHANGE MASTER TO
   MASTER_HOST='master2.mycompany.com',
   MASTER_USER='replication',
   MASTER_PASSWORD='bigs3cret',
   MASTER_PORT=3306,
   MASTER_LOG_FILE='master2-bin.001',
   MASTER_LOG_POS=4,
   MASTER_CONNECT_RETRY=10;
START SLAVE;

See Also

1.1.1.2.5.2 START SLAVE

The terms master and slave have historically been used in replication, but the terms terms primary and replica are now preferred. The old terms are used still used in parts of the documentation, and in MariaDB commands, although MariaDB 10.5 has begun the process of renaming. The documentation process is ongoing. See MDEV-18777 to follow progress on this effort.

Syntax

START SLAVE ["connection_name"] [thread_type [, thread_type] ... ] [FOR CHANNEL "connection_name"]
START SLAVE ["connection_name"] [SQL_THREAD] UNTIL                
    MASTER_LOG_FILE = 'log_name', MASTER_LOG_POS = log_pos [FOR CHANNEL "connection_name"]
START SLAVE ["connection_name"] [SQL_THREAD] UNTIL
    RELAY_LOG_FILE = 'log_name', RELAY_LOG_POS = log_pos [FOR CHANNEL "connection_name"]
START SLAVE ["connection_name"] [SQL_THREAD] UNTIL
    MASTER_GTID_POS = <GTID position> [FOR CHANNEL "connection_name"]
START ALL SLAVES [thread_type [, thread_type]]

START REPLICA ["connection_name"] [thread_type [, thread_type] ... ] -- from 10.5.1
START REPLICA ["connection_name"] [SQL_THREAD] UNTIL                
    MASTER_LOG_FILE = 'log_name', MASTER_LOG_POS = log_pos -- from 10.5.1
START REPLICA ["connection_name"] [SQL_THREAD] UNTIL
    RELAY_LOG_FILE = 'log_name', RELAY_LOG_POS = log_pos -- from 10.5.1
START REPLICA ["connection_name"] [SQL_THREAD] UNTIL
    MASTER_GTID_POS = <GTID position> -- from 10.5.1
START ALL REPLICAS [thread_type [, thread_type]] -- from 10.5.1

thread_type: IO_THREAD | SQL_THREAD

Contents

  1. Syntax
  2. Description
    1. START SLAVE UNTIL
    2. connection_name
    3. START ALL SLAVES
    4. START REPLICA
  3. See Also

Description

START SLAVE (START REPLICA from MariaDB 10.5.1) with no thread_type options starts both of the replica threads (see replication). The I/O thread reads events from the primary server and stores them in the relay log. The SQL thread reads events from the relay log and executes them. START SLAVE requires the SUPER privilege, or, from MariaDB 10.5.2, the REPLICATION SLAVE ADMIN privilege.

If START SLAVE succeeds in starting the replica threads, it returns without any error. However, even in that case, it might be that the replica threads start and then later stop (for example, because they do not manage to connect to the primary or read its binary log, or some other problem). START SLAVE does not warn you about this. You must check the replica's error log for error messages generated by the replica threads, or check that they are running satisfactorily with SHOW SLAVE STATUS (SHOW REPLICA STATUS from MariaDB 10.5.1).

START SLAVE UNTIL

START SLAVE UNTIL refers to the SQL_THREAD replica position at which the SQL_THREAD replication will halt. If SQL_THREAD isn't specified both threads are started.

START SLAVE UNTIL master_gtid_pos=xxx is also supported. See Global Transaction ID/START SLAVE UNTIL master_gtid_pos=xxx for more details.

connection_name

If there is only one nameless primary, or the default primary (as specified by the default_master_connection system variable) is intended, connection_name can be omitted. If provided, the START SLAVE statement will apply to the specified primary. connection_name is case-insensitive.

MariaDB starting with 10.7.0

The FOR CHANNEL keyword was added for MySQL compatibility. This is identical as using the channel_name directly after START SLAVE.

START ALL SLAVES

START ALL SLAVES starts all configured replicas (replicas with master_host not empty) that were not started before. It will give a note for all started connections. You can check the notes with SHOW WARNINGS.

START REPLICA

MariaDB starting with 10.5.1

START REPLICA is an alias for START SLAVE from MariaDB 10.5.1.

See Also

1.1.1.2.5.3 STOP SLAVE

The terms master and slave have historically been used in replication, but the terms terms primary and replica are now preferred. The old terms are used still used in parts of the documentation, and in MariaDB commands, although MariaDB 10.5 has begun the process of renaming. The documentation process is ongoing. See MDEV-18777 to follow progress on this effort.

Syntax

STOP SLAVE ["connection_name"] [thread_type [, thread_type] ... ] [FOR CHANNEL "connection_name"]

STOP ALL SLAVES [thread_type [, thread_type]]

STOP REPLICA ["connection_name"] [thread_type [, thread_type] ... ] -- from 10.5.1

STOP ALL REPLICAS [thread_type [, thread_type]] -- from 10.5.1

thread_type: IO_THREAD | SQL_THREAD

Contents

  1. Syntax
  2. Description
    1. STOP ALL SLAVES
    2. connection_name
    3. STOP REPLICA
  3. See Also

Description

Stops the replica threads. STOP SLAVE requires the SUPER privilege, or, from MariaDB 10.5.2, the REPLICATION SLAVE ADMIN privilege.

Like START SLAVE, this statement may be used with the IO_THREAD and SQL_THREAD options to name the thread or threads to be stopped. In almost all cases, one never need to use the thread_type options.

STOP SLAVE waits until any current replication event group affecting one or more non-transactional tables has finished executing (if there is any such replication group), or until the user issues a KILL QUERY or KILL CONNECTION statement.

Note that STOP SLAVE doesn't delete the connection permanently. Next time you execute START SLAVE or the MariaDB server restarts, the replica connection is restored with it's original arguments. If you want to delete a connection, you should execute RESET SLAVE.

STOP ALL SLAVES

STOP ALL SLAVES stops all your running replicas. It will give you a note for every stopped connection. You can check the notes with SHOW WARNINGS.

connection_name

The connection_name option is used for multi-source replication.

If there is only one nameless master, or the default master (as specified by the default_master_connection system variable) is intended, connection_name can be omitted. If provided, the STOP SLAVE statement will apply to the specified master. connection_name is case-insensitive.

MariaDB starting with 10.7.0

The FOR CHANNEL keyword was added for MySQL compatibility. This is identical as using the channel_name directly after STOP SLAVE.

STOP REPLICA

MariaDB starting with 10.5.1

STOP REPLICA is an alias for STOP SLAVE from MariaDB 10.5.1.

See Also

  • CHANGE MASTER TO is used to create and change connections.
  • START SLAVE is used to start a predefined connection.
  • RESET SLAVE is used to reset parameters for a connection and also to permanently delete a master connection.

1.1.1.2.5.4 RESET SLAVE

The terms master and slave have historically been used in replication, but the terms terms primary and replica are now preferred. The old terms are used still used in parts of the documentation, and in MariaDB commands, although MariaDB 10.5 has begun the process of renaming. The documentation process is ongoing. See MDEV-18777 to follow progress on this effort.

Syntax

RESET SLAVE ["connection_name"] [ALL]  [FOR CHANNEL "connection_name"]

Contents

  1. Syntax
  2. Description
    1. connection_name
    2. RESET REPLICA
  3. See Also

Description

RESET SLAVE makes the slave forget its replication position in the master's binary log. This statement is meant to be used for a clean start. It deletes the master.info and relay-log.info files, all the relay log files, and starts a new relay log file. To use RESET SLAVE, the slave replication threads must be stopped (use STOP SLAVE if necessary).

Note: All relay log files are deleted, even if they have not been completely executed by the slave SQL thread. (This is a condition likely to exist on a replication slave if you have issued a STOP SLAVE statement or if the slave is highly loaded.)

Note: RESET REPLICA does not reset the global gtid_slave_pos variable. This means that a replica server configured with CHANGE MASTER TO MASTER_USE_GTID=slave_pos will not receive events with GTIDs occurring before the state saved in gtid_slave_pos. If the intent is to reprocess these events, gtid_slave_pos must be manually reset, e.g. by executing set global gtid_slave_pos="".

Connection information stored in the master.info file is immediately reset using any values specified in the corresponding startup options. This information includes values such as master host, master port, master user, and master password. If the slave SQL thread was in the middle of replicating temporary tables when it was stopped, and RESET SLAVE is issued, these replicated temporary tables are deleted on the slave.

The ALL also resets the PORT, HOST, USER and PASSWORD parameters for the slave. If you are using a connection name, it will permanently delete it and it will not show up anymore in SHOW ALL SLAVES STATUS.

connection_name

The connection_name option is used for multi-source replication.

If there is only one nameless master, or the default master (as specified by the default_master_connection system variable) is intended, connection_name can be omitted. If provided, the RESET SLAVE statement will apply to the specified master. connection_name is case-insensitive.

MariaDB starting with 10.7.0

The FOR CHANNEL keyword was added for MySQL compatibility. This is identical as using the channel_name directly after RESET SLAVE.

RESET REPLICA

MariaDB starting with 10.5.1

RESET REPLICA is an alias for RESET SLAVE from MariaDB 10.5.1.

See Also

  • STOP SLAVE stops the slave, but it can be restarted with START SLAVE or after next MariaDB server restart.

1.1.1.2.5.5 SET GLOBAL SQL_SLAVE_SKIP_COUNTER

Syntax

SET GLOBAL sql_slave_skip_counter = N

Contents

  1. Syntax
  2. Description
  3. Example
  4. Multiple Replication Domains
  5. See Also

Description

This statement skips the next N events from the primary. This is useful for recovering from replication stops caused by a statement.

If multi-source replication is used, this statement applies to the default connection. It could be necessary to change the value of the default_master_connection system variable.

Note that, if the event is a transaction, the whole transaction will be skipped. With non-transactional engines, an event is always a single statement.

This statement is valid only when the replica threads are not running. Otherwise, it produces an error.

The statement does not automatically restart the replica threads.

Example

SHOW SLAVE STATUS \G
...
SET GLOBAL sql_slave_skip_counter = 1;
START SLAVE;

Multi-source replication:

SET @@default_master_connection = 'master_01';
SET GLOBAL SQL_SLAVE_SKIP_COUNTER = 1;
START SLAVE;

Multiple Replication Domains

sql_slave_skip_counter can't be used to skip transactions on a replica if GTID replication is in use and if gtid_slave_pos contains multiple gtid_domain_id values. In that case, you'll get an error like the following:

ERROR 1966 (HY000): When using parallel replication and GTID with multiple 
 replication domains, @@sql_slave_skip_counter can not be used. Instead, 
 setting @@gtid_slave_pos explicitly can be  used to skip to after a given GTID 
 position.

In order to skip transactions in cases like this, you will have to manually change gtid_slave_pos.

See Also

1.1.1.2.5.6 SHOW RELAYLOG EVENTS

The terms master and slave have historically been used in replication, but the terms terms primary and replica are now preferred. The old terms are used still used in parts of the documentation, and in MariaDB commands, although MariaDB 10.5 has begun the process of renaming. The documentation process is ongoing. See MDEV-18777 to follow progress on this effort.

Syntax

SHOW RELAYLOG ['connection_name'] EVENTS
    [IN 'log_name'] [FROM pos] [LIMIT [offset,] row_count]
    [ FOR CHANNEL 'channel_name']

Description

On replicas, this command shows the events in the relay log. If 'log_name' is not specified, the first relay log is shown.

Syntax for the LIMIT clause is the same as for SELECT ... LIMIT.

Using the LIMIT clause is highly recommended because the SHOW RELAYLOG EVENTS command returns the complete contents of the relay log, which can be quite large.

This command does not return events related to setting user and system variables. If you need those, use mariadb-binlog/mysqlbinlog.

On the primary, this command does nothing.

Requires the REPLICA MONITOR privilege (>= MariaDB 10.5.9), the REPLICATION SLAVE ADMIN privilege (>= MariaDB 10.5.2) or the REPLICATION SLAVE privilege (<= MariaDB 10.5.1).

connection_name

If there is only one nameless primary, or the default primary (as specified by the default_master_connection system variable) is intended, connection_name can be omitted. If provided, the SHOW RELAYLOG statement will apply to the specified primary. connection_name is case-insensitive.

MariaDB starting with 10.7.0

The FOR CHANNEL keyword was added for MySQL compatibility. This is identical as using the channel_name directly after SHOW RELAYLOG.

1.1.1.2.5.7 SHOW SLAVE STATUS

Syntax

SHOW SLAVE ["connection_name"] STATUS [FOR CHANNEL "connection_name"]
SHOW REPLICA ["connection_name"] STATUS -- From MariaDB 10.5.1

or

SHOW ALL SLAVES STATUS
SHOW ALL REPLICAS STATUS -- From MariaDB 10.5.1

Contents

  1. Syntax
  2. Description
    1. Multi-Source
    2. Column Descriptions
    3. SHOW REPLICA STATUS
  3. Examples
  4. See Also

Description

This statement is to be run on a replica and provides status information on essential parameters of the replica threads.

This statement requires the SUPER privilege, the REPLICATION_CLIENT privilege, or, from MariaDB 10.5.2, the REPLICATION SLAVE ADMIN privilege, or, from MariaDB 10.5.9, the REPLICA MONITOR privilege.

Multi-Source

The FULL and "connection_name" options allow you to connect to many primaries at the same time.

ALL SLAVES (or ALL REPLICAS from MariaDB 10.5.1) gives you a list of all connections to the primary nodes.

The rows will be sorted according to Connection_name.

If you specify a connection_name, you only get the information about that connection. If connection_name is not used, then the name set by default_master_connection is used. If the connection name doesn't exist you will get an error: There is no master connection for 'xxx'.

MariaDB starting with 10.7.0

The FOR CHANNEL keyword was added for MySQL compatibility. This is identical as using the channel_name directly after SHOW SLAVE.

Column Descriptions

NameDescriptionAdded
Connection_nameName of the primary connection. Returned with SHOW ALL SLAVES STATUS (or SHOW ALL REPLICAS STATUS from MariaDB 10.5.1) only.
Slave_SQL_StateState of SQL thread. Returned with SHOW ALL SLAVES STATUS (or SHOW ALL REPLICAS STATUS from MariaDB 10.5.1) only. See Slave SQL Thread States.
Slave_IO_StateState of I/O thread. See Slave I/O Thread States.
Master_hostMaster host that the replica is connected to.
Master_userAccount user name being used to connect to the primary.
Master_portThe port being used to connect to the primary.
Connect_RetryTime in seconds between retries to connect. The default is 60. The CHANGE MASTER TO statement can set this. The master-retry-count option determines the maximum number of reconnection attempts.
Master_Log_FileName of the primary binary log file that the I/O thread is currently reading from.
Read_Master_Log_PosPosition up to which the I/O thread has read in the current primary binary log file.
Relay_Log_FileName of the relay log file that the SQL thread is currently processing.
Relay_Log_PosPosition up to which the SQL thread has finished processing in the current relay log file.
Relay_Master_Log_FileName of the primary binary log file that contains the most recent event executed by the SQL thread.
Slave_IO_RunningWhether the replica I/O thread is running and connected (Yes), running but not connected to a primary (Connecting) or not running (No).
Slave_SQL_RunningWhether or not the SQL thread is running.
Replicate_Do_DBDatabases specified for replicating with the replicate_do_db option.
Replicate_Ignore_DBDatabases specified for ignoring with the replicate_ignore_db option.
Replicate_Do_TableTables specified for replicating with the replicate_do_table option.
Replicate_Ignore_TableTables specified for ignoring with the replicate_ignore_table option.
Replicate_Wild_Do_TableTables specified for replicating with the replicate_wild_do_table option.
Replicate_Wild_Ignore_TableTables specified for ignoring with the replicate_wild_ignore_table option.
Last_ErrnoAlias for Last_SQL_Errno (see below)
Last ErrorAlias for Last_SQL_Error (see below)
Skip_CounterNumber of events that a replica skips from the master, as recorded in the sql_slave_skip_counter system variable.
Exec_Master_Log_PosPosition up to which the SQL thread has processed in the current master binary log file. Can be used to start a new replica from a current replica with the CHANGE MASTER TO ... MASTER_LOG_POS option.
Relay_Log_SpaceTotal size of all relay log files combined.
Until_Condition
Until_Log_FileThe MASTER_LOG_FILE value of the START SLAVE UNTIL condition.
Until_Log_PosThe MASTER_LOG_POS value of the START SLAVE UNTIL condition.
Master_SSL_AllowedWhether an SSL connection is permitted (Yes), not permitted (No) or permitted but without the replica having SSL support enabled (Ignored)
Master_SSL_CA_FileThe MASTER_SSL_CA option of the CHANGE MASTER TO statement.
Master_SSL_CA_PathThe MASTER_SSL_CAPATH option of the CHANGE MASTER TO statement.
Master_SSL_CertThe MASTER_SSL_CERT option of the CHANGE MASTER TO statement.
Master_SSL_CipherThe MASTER_SSL_CIPHER option of the CHANGE MASTER TO statement.
Master_SSL_KeyThe MASTER_SSL_KEY option of the CHANGE MASTER TO statement.
Seconds_Behind_MasterDifference between the timestamp logged on the master for the event that the replica is currently processing, and the current timestamp on the replica. Zero if the replica is not currently processing an event. With parallel replication, seconds_behind_master is updated only after transactions commit.
Master_SSL_Verify_Server_CertThe MASTER_SSL_VERIFY_SERVER_CERT option of the CHANGE MASTER TO statement.
Last_IO_ErrnoError code of the most recent error that caused the I/O thread to stop (also recorded in the replica's error log). 0 means no error. RESET SLAVE or RESET MASTER will reset this value.
Last_IO_ErrorError message of the most recent error that caused the I/O thread to stop (also recorded in the replica's error log). An empty string means no error. RESET SLAVE or RESET MASTER will reset this value.
Last_SQL_ErrnoError code of the most recent error that caused the SQL thread to stop (also recorded in the replica's error log). 0 means no error. RESET SLAVE or RESET MASTER will reset this value.
Last_SQL_ErrorError message of the most recent error that caused the SQL thread to stop (also recorded in the replica's error log). An empty string means no error. RESET SLAVE or RESET MASTER will reset this value.
Replicate_Ignore_Server_IdsList of server_ids that are currently being ignored for replication purposes, or an empty string for none, as specified in the IGNORE_SERVER_IDS option of the CHANGE MASTER TO statement.
Master_Server_IdThe master's server_id value.
Master_SSL_CrlThe MASTER_SSL_CRL option of the CHANGE MASTER TO statement.
Master_SSL_CrlpathThe MASTER_SSL_CRLPATH option of the CHANGE MASTER TO statement.
Using_GtidWhether or not global transaction ID's are being used for replication (can be No, Slave_Pos, or Current_Pos).
Gtid_IO_PosCurrent global transaction ID value.
Retried_transactionsNumber of retried transactions for this connection. Returned with SHOW ALL SLAVES STATUS only.
Max_relay_log_sizeMax relay log size for this connection. Returned with SHOW ALL SLAVES STATUS only.
Executed_log_entriesHow many log entries the replica has executed. Returned with SHOW ALL SLAVES STATUS only.
Slave_received_heartbeatsHow many heartbeats we have got from the master. Returned with SHOW ALL SLAVES STATUS only.
Slave_heartbeat_periodHow often to request a heartbeat packet from the master (in seconds). Returned with SHOW ALL SLAVES STATUS only.
Gtid_Slave_PosGTID of the last event group replicated on a replica server, for each replication domain, as stored in the gtid_slave_pos system variable. Returned with SHOW ALL SLAVES STATUS only.
SQL_DelayValue specified by MASTER_DELAY in CHANGE MASTER (or 0 if none).MariaDB 10.2.3
SQL_Remaining_DelayWhen the replica is delaying the execution of an event due to MASTER_DELAY, this is the number of seconds of delay remaining before the event will be applied. Otherwise, the value is NULL.MariaDB 10.2.3
Slave_SQL_Running_StateThe state of the SQL driver threads, same as in SHOW PROCESSLIST. When the replica is delaying the execution of an event due to MASTER_DELAY, this field displays: "Waiting until MASTER_DELAY seconds after master executed event".MariaDB 10.2.3
Slave_DDL_GroupsThis status variable counts the occurrence of DDL statements. This is a replica-side counter for optimistic parallel replication.MariaDB 10.3.7
Slave_Non_Transactional_GroupsThis status variable counts the occurrence of non-transactional event groups. This is a replica-side counter for optimistic parallel replication.MariaDB 10.3.7
Slave_Transactional_GroupsThis status variable counts the occurrence of transactional event groups. This is a replica-side counter for optimistic parallel replication.MariaDB 10.3.7

SHOW REPLICA STATUS

MariaDB starting with 10.5.1

SHOW REPLICA STATUS is an alias for SHOW SLAVE STATUS from MariaDB 10.5.1.

Examples

If you issue this statement using the mysql client, you can use a \G statement terminator rather than a semicolon to obtain a more readable vertical layout.

SHOW SLAVE STATUS\G
*************************** 1. row ***************************
               Slave_IO_State: Waiting for master to send event
                  Master_Host: db01.example.com
                  Master_User: replicant
                  Master_Port: 3306
                Connect_Retry: 60
              Master_Log_File: mariadb-bin.000010
          Read_Master_Log_Pos: 548
               Relay_Log_File: relay-bin.000004
                Relay_Log_Pos: 837
        Relay_Master_Log_File: mariadb-bin.000010
             Slave_IO_Running: Yes
            Slave_SQL_Running: Yes
              Replicate_Do_DB: 
          Replicate_Ignore_DB: 
           Replicate_Do_Table: 
       Replicate_Ignore_Table: 
      Replicate_Wild_Do_Table: 
  Replicate_Wild_Ignore_Table: 
                   Last_Errno: 0
                   Last_Error: 
                 Skip_Counter: 0
          Exec_Master_Log_Pos: 548
              Relay_Log_Space: 1497
              Until_Condition: None
               Until_Log_File: 
                Until_Log_Pos: 0
           Master_SSL_Allowed: No
           Master_SSL_CA_File: 
           Master_SSL_CA_Path: 
              Master_SSL_Cert: 
            Master_SSL_Cipher: 
               Master_SSL_Key: 
        Seconds_Behind_Master: 0
Master_SSL_Verify_Server_Cert: No
                Last_IO_Errno: 0
                Last_IO_Error: 
               Last_SQL_Errno: 0
               Last_SQL_Error: 
  Replicate_Ignore_Server_Ids: 
             Master_Server_Id: 101
               Master_SSL_Crl: 
           Master_SSL_Crlpath: 
                   Using_Gtid: No
                  Gtid_IO_Pos: 

SHOW ALL SLAVES STATUS\G
*************************** 1. row ***************************
              Connection_name: 
              Slave_SQL_State: Slave has read all relay log; waiting for the slave I/O thread to update it
               Slave_IO_State: Waiting for master to send event
                  Master_Host: db01.example.com
                  Master_User: replicant
                  Master_Port: 3306
                Connect_Retry: 60
              Master_Log_File: mariadb-bin.000010
          Read_Master_Log_Pos: 3608
               Relay_Log_File: relay-bin.000004
                Relay_Log_Pos: 3897
        Relay_Master_Log_File: mariadb-bin.000010
             Slave_IO_Running: Yes
            Slave_SQL_Running: Yes
              Replicate_Do_DB: 
          Replicate_Ignore_DB: 
           Replicate_Do_Table: 
       Replicate_Ignore_Table: 
      Replicate_Wild_Do_Table: 
  Replicate_Wild_Ignore_Table: 
                   Last_Errno: 0
                   Last_Error: 
                 Skip_Counter: 0
          Exec_Master_Log_Pos: 3608
              Relay_Log_Space: 4557
              Until_Condition: None
               Until_Log_File: 
                Until_Log_Pos: 0
           Master_SSL_Allowed: No
           Master_SSL_CA_File: 
           Master_SSL_CA_Path: 
              Master_SSL_Cert: 
            Master_SSL_Cipher: 
               Master_SSL_Key: 
        Seconds_Behind_Master: 0
Master_SSL_Verify_Server_Cert: No
                Last_IO_Errno: 0
                Last_IO_Error: 
               Last_SQL_Errno: 0
               Last_SQL_Error: 
  Replicate_Ignore_Server_Ids: 
             Master_Server_Id: 101
               Master_SSL_Crl: 
           Master_SSL_Crlpath: 
                   Using_Gtid: No
                  Gtid_IO_Pos:
         Retried_transactions: 0
           Max_relay_log_size: 104857600
         Executed_log_entries: 40
    Slave_received_heartbeats: 11
       Slave_heartbeat_period: 1800.000
               Gtid_Slave_Pos: 0-101-2320

You can also access some of the variables directly from status variables:

SET @@default_master_connection="test" ;
show status like "%slave%"

Variable_name   Value
Com_show_slave_hosts    0
Com_show_slave_status   0
Com_start_all_slaves    0
Com_start_slave 0
Com_stop_all_slaves     0
Com_stop_slave  0
Rpl_semi_sync_slave_status      OFF
Slave_connections       0
Slave_heartbeat_period  1800.000
Slave_open_temp_tables  0
Slave_received_heartbeats       0
Slave_retried_transactions      0
Slave_running   OFF
Slaves_connected        0
Slaves_running  1

See Also

1.1.1.2.5.8 SHOW MASTER STATUS

Syntax

SHOW MASTER STATUS
SHOW BINLOG STATUS -- From MariaDB 10.5.2

Description

Provides status information about the binary log files of the primary.

This statement requires the SUPER privilege, the REPLICATION_CLIENT privilege, or, from MariaDB 10.5.2, the BINLOG MONITOR privilege.

To see information about the current GTIDs in the binary log, use the gtid_binlog_pos variable.

SHOW MASTER STATUS was renamed to SHOW BINLOG STATUS in MariaDB 10.5.2, but the old name remains an alias for compatibility purposes.

Example

SHOW MASTER STATUS;
+--------------------+----------+--------------+------------------+
| File               | Position | Binlog_Do_DB | Binlog_Ignore_DB |
+--------------------+----------+--------------+------------------+
| mariadb-bin.000016 |      475 |              |                  |
+--------------------+----------+--------------+------------------+
SELECT @@global.gtid_binlog_pos;
+--------------------------+
| @@global.gtid_binlog_pos |
+--------------------------+
| 0-1-2                    |
+--------------------------+

See Also

1.1.1.2.5.9 SHOW SLAVE HOSTS

Contents

  1. Syntax
  2. Description
    1. SHOW REPLICA HOSTS
  3. See Also

Syntax

SHOW SLAVE HOSTS
SHOW REPLICA HOSTS -- from MariaDB 10.5.1

Description

This command is run on the primary and displays a list of replicas that are currently registered with it. Only replicas started with the --report-host=host_name option are visible in this list.

The list is displayed on any server (not just the primary server). The output looks like this:

SHOW SLAVE HOSTS;
+------------+-----------+------+-----------+
| Server_id  | Host      | Port | Master_id |
+------------+-----------+------+-----------+
|  192168010 | iconnect2 | 3306 | 192168011 |
| 1921680101 | athena    | 3306 | 192168011 |
+------------+-----------+------+-----------+
  • Server_id: The unique server ID of the replica server, as configured in the server's option file, or on the command line with --server-id=value.
  • Host: The host name of the replica server, as configured in the server's option file, or on the command line with --report-host=host_name. Note that this can differ from the machine name as configured in the operating system.
  • Port: The port the replica server is listening on.
  • Master_id: The unique server ID of the primary server that the replica server is replicating from.

Some MariaDB and MySQL versions report another variable, rpl_recovery_rank. This variable was never used, and was eventually removed in MariaDB 10.1.2 .

Requires the REPLICATION MASTER ADMIN privilege (>= MariaDB 10.5.2) or the REPLICATION SLAVE privilege (<= MariaDB 10.5.1).

SHOW REPLICA HOSTS

MariaDB starting with 10.5.1

SHOW REPLICA HOSTS is an alias for SHOW SLAVE HOSTS from MariaDB 10.5.1.

See Also

1.1.1.2.5.10 RESET MASTER

RESET MASTER [TO #]

Deletes all binary log files listed in the index file, resets the binary log index file to be empty, and creates a new binary log file with a suffix of .000001.

If TO # is given, then the first new binary log file will start from number #.

This statement is for use only when the master is started for the first time, and should never be used if any slaves are actively replicating from the binary log.

See Also

1.1.1.2.6 Plugin SQL Statements

Plugin commands.

1.1.1.2.6.1 SHOW PLUGINS

Syntax

SHOW PLUGINS;

Contents

  1. Syntax
  2. Description
  3. Examples
  4. See Also

Description

SHOW PLUGINS displays information about installed plugins. The Library column indicates the plugin library - if it is NULL, the plugin is built-in and cannot be uninstalled.

The PLUGINS table in the information_schema database contains more detailed information.

For specific information about storage engines (a particular type of plugin), see the information_schema.ENGINES table and the SHOW ENGINES statement.

Examples

SHOW PLUGINS;
+----------------------------+----------+--------------------+-------------+---------+
| Name                       | Status   | Type               | Library     | License |
+----------------------------+----------+--------------------+-------------+---------+
| binlog                     | ACTIVE   | STORAGE ENGINE     | NULL        | GPL     |
| mysql_native_password      | ACTIVE   | AUTHENTICATION     | NULL        | GPL     |
| mysql_old_password         | ACTIVE   | AUTHENTICATION     | NULL        | GPL     |
| MRG_MyISAM                 | ACTIVE   | STORAGE ENGINE     | NULL        | GPL     |
| MyISAM                     | ACTIVE   | STORAGE ENGINE     | NULL        | GPL     |
| CSV                        | ACTIVE   | STORAGE ENGINE     | NULL        | GPL     |
| MEMORY                     | ACTIVE   | STORAGE ENGINE     | NULL        | GPL     |
| FEDERATED                  | ACTIVE   | STORAGE ENGINE     | NULL        | GPL     |
| PERFORMANCE_SCHEMA         | ACTIVE   | STORAGE ENGINE     | NULL        | GPL     |
| Aria                       | ACTIVE   | STORAGE ENGINE     | NULL        | GPL     |
| InnoDB                     | ACTIVE   | STORAGE ENGINE     | NULL        | GPL     |
| INNODB_TRX                 | ACTIVE   | INFORMATION SCHEMA | NULL        | GPL     |
...
| INNODB_SYS_FOREIGN         | ACTIVE   | INFORMATION SCHEMA | NULL        | GPL     |
| INNODB_SYS_FOREIGN_COLS    | ACTIVE   | INFORMATION SCHEMA | NULL        | GPL     |
| SPHINX                     | ACTIVE   | STORAGE ENGINE     | NULL        | GPL     |
| ARCHIVE                    | ACTIVE   | STORAGE ENGINE     | NULL        | GPL     |
| BLACKHOLE                  | ACTIVE   | STORAGE ENGINE     | NULL        | GPL     |
| FEEDBACK                   | DISABLED | INFORMATION SCHEMA | NULL        | GPL     |
| partition                  | ACTIVE   | STORAGE ENGINE     | NULL        | GPL     |
| pam                        | ACTIVE   | AUTHENTICATION     | auth_pam.so | GPL     |
+----------------------------+----------+--------------------+-------------+---------+

See Also

1.1.1.2.6.2 SHOW PLUGINS SONAME

Syntax

SHOW PLUGINS SONAME { library | LIKE 'pattern' | WHERE expr };

Description

SHOW PLUGINS SONAME displays information about compiled-in and all server plugins in the plugin_dir directory, including plugins that haven't been installed.

Examples

SHOW PLUGINS SONAME 'ha_example.so';
+----------+---------------+----------------+---------------+---------+
| Name     | Status        | Type           | Library       | License |
+----------+---------------+----------------+---------------+---------+
| EXAMPLE  | NOT INSTALLED | STORAGE ENGINE | ha_example.so | GPL     |
| UNUSABLE | NOT INSTALLED | DAEMON         | ha_example.so | GPL     |
+----------+---------------+----------------+---------------+---------+

There is also a corresponding information_schema table, called ALL_PLUGINS, which contains more complete information.

1.1.1.2.6.3 INSTALL PLUGIN

Syntax

INSTALL PLUGIN [IF NOT EXISTS] plugin_name SONAME 'plugin_library'

Contents

  1. Syntax
  2. Description
    1. IF NOT EXISTS
  3. Examples
  4. See Also

Description

This statement installs an individual plugin from the specified library. To install the whole library (which could be required), use INSTALL SONAME. See also Installing a Plugin.

plugin_name is the name of the plugin as defined in the plugin declaration structure contained in the library file. Plugin names are not case sensitive. For maximal compatibility, plugin names should be limited to ASCII letters, digits, and underscore, because they are used in C source files, shell command lines, M4 and Bourne shell scripts, and SQL environments.

plugin_library is the name of the shared library that contains the plugin code. The file name extension can be omitted (which makes the statement look the same on all architectures).

The shared library must be located in the plugin directory (that is, the directory named by the plugin_dir system variable). The library must be in the plugin directory itself, not in a subdirectory. By default, plugin_dir is plugin directory under the directory named by the pkglibdir configuration variable, but it can be changed by setting the value of plugin_dir at server startup. For example, set its value in a my.cnf file:

[mysqld]
plugin_dir=/path/to/plugin/directory

If the value of plugin_dir is a relative path name, it is taken to be relative to the MySQL base directory (the value of the basedir system variable).

INSTALL PLUGIN adds a line to the mysql.plugin table that describes the plugin. This table contains the plugin name and library file name.

INSTALL PLUGIN causes the server to read option (my.cnf) files just as during server startup. This enables the plugin to pick up any relevant options from those files. It is possible to add plugin options to an option file even before loading a plugin (if the loose prefix is used). It is also possible to uninstall a plugin, edit my.cnf, and install the plugin again. Restarting the plugin this way enables it to the new option values without a server restart.

INSTALL PLUGIN also loads and initializes the plugin code to make the plugin available for use. A plugin is initialized by executing its initialization function, which handles any setup that the plugin must perform before it can be used.

To use INSTALL PLUGIN, you must have the INSERT privilege for the mysql.plugin table.

At server startup, the server loads and initializes any plugin that is listed in the mysql.plugin table. This means that a plugin is installed with INSTALL PLUGIN only once, not every time the server starts. Plugin loading at startup does not occur if the server is started with the --skip-grant-tables option.

When the server shuts down, it executes the de-initialization function for each plugin that is loaded so that the plugin has a chance to perform any final cleanup.

If you need to load plugins for a single server startup when the --skip-grant-tables option is given (which tells the server not to read system tables), use the --plugin-load mysqld option.

MariaDB starting with 10.4.0

IF NOT EXISTS

When the IF NOT EXISTS clause is used, MariaDB will return a note instead of an error if the specified plugin already exists. See SHOW WARNINGS.

Examples

INSTALL PLUGIN sphinx SONAME 'ha_sphinx.so';

The extension can also be omitted:

INSTALL PLUGIN innodb SONAME 'ha_xtradb';

From MariaDB 10.4.0:

INSTALL PLUGIN IF NOT EXISTS example SONAME 'ha_example';
Query OK, 0 rows affected (0.104 sec)

INSTALL PLUGIN IF NOT EXISTS example SONAME 'ha_example';
Query OK, 0 rows affected, 1 warning (0.000 sec)

SHOW WARNINGS;
+-------+------+------------------------------------+
| Level | Code | Message                            |
+-------+------+------------------------------------+
| Note  | 1968 | Plugin 'example' already installed |
+-------+------+------------------------------------+

See Also

1.1.1.2.6.4 UNINSTALL PLUGIN

Syntax

UNINSTALL PLUGIN [IF EXISTS] plugin_name

Contents

  1. Syntax
  2. Description
    1. IF EXISTS
  3. Examples
  4. See Also

Description

This statement removes a single installed plugin. To uninstall the whole library which contains the plugin, use UNINSTALL SONAME. You cannot uninstall a plugin if any table that uses it is open.

plugin_name must be the name of some plugin that is listed in the mysql.plugin table. The server executes the plugin's deinitialization function and removes the row for the plugin from the mysql.plugin table, so that subsequent server restarts will not load and initialize the plugin. UNINSTALL PLUGIN does not remove the plugin's shared library file.

To use UNINSTALL PLUGIN, you must have the DELETE privilege for the mysql.plugin table.

MariaDB starting with 10.4.0

IF EXISTS

If the IF EXISTS clause is used, MariaDB will return a note instead of an error if the plugin does not exist. See SHOW WARNINGS.

Examples

UNINSTALL PLUGIN example;

From MariaDB 10.4.0:

UNINSTALL PLUGIN IF EXISTS example;
Query OK, 0 rows affected (0.099 sec)

UNINSTALL PLUGIN IF EXISTS example;
Query OK, 0 rows affected, 1 warning (0.000 sec)

SHOW WARNINGS;
+-------+------+-------------------------------+
| Level | Code | Message                       |
+-------+------+-------------------------------+
| Note  | 1305 | PLUGIN example does not exist |
+-------+------+-------------------------------+

See Also

1.1.1.2.6.5 INSTALL SONAME

Syntax

INSTALL SONAME 'plugin_library'

Contents

  1. Syntax
  2. Description
  3. Examples
  4. See Also

Description

This statement is a variant of INSTALL PLUGIN. It installs all plugins from a given plugin_library. See INSTALL PLUGIN for details.

plugin_library is the name of the shared library that contains the plugin code. The file name extension (for example, libmyplugin.so or libmyplugin.dll) can be omitted (which makes the statement look the same on all architectures).

The shared library must be located in the plugin directory (that is, the directory named by the plugin_dir system variable). The library must be in the plugin directory itself, not in a subdirectory. By default, plugin_dir is plugin directory under the directory named by the pkglibdir configuration variable, but it can be changed by setting the value of plugin_dir at server startup. For example, set its value in a my.cnf file:

[mysqld]
plugin_dir=/path/to/plugin/directory

If the value of plugin_dir is a relative path name, it is taken to be relative to the MySQL base directory (the value of the basedir system variable).

INSTALL SONAME adds one or more lines to the mysql.plugin table that describes the plugin. This table contains the plugin name and library file name.

INSTALL SONAME causes the server to read option (my.cnf) files just as during server startup. This enables the plugin to pick up any relevant options from those files. It is possible to add plugin options to an option file even before loading a plugin (if the loose prefix is used). It is also possible to uninstall a plugin, edit my.cnf, and install the plugin again. Restarting the plugin this way enables it to the new option values without a server restart.

INSTALL SONAME also loads and initializes the plugin code to make the plugin available for use. A plugin is initialized by executing its initialization function, which handles any setup that the plugin must perform before it can be used.

To use INSTALL SONAME, you must have the INSERT privilege for the mysql.plugin table.

At server startup, the server loads and initializes any plugin that is listed in the mysql.plugin table. This means that a plugin is installed with INSTALL SONAME only once, not every time the server starts. Plugin loading at startup does not occur if the server is started with the --skip-grant-tables option.

When the server shuts down, it executes the de-initialization function for each plugin that is loaded so that the plugin has a chance to perform any final cleanup.

If you need to load plugins for a single server startup when the --skip-grant-tables option is given (which tells the server not to read system tables), use the --plugin-load mysqld option.

If you need to install only one plugin from a library, use the INSTALL PLUGIN statement.

Examples

To load the XtraDB storage engine and all of its information_schema tables with one statement, use

INSTALL SONAME 'ha_xtradb';

This statement can be used instead of INSTALL PLUGIN even when the library contains only one plugin:

INSTALL SONAME 'ha_sequence';

See Also

1.1.1.2.6.6 UNINSTALL SONAME

Syntax

UNINSTALL SONAME  [IF EXISTS] 'plugin_library'

Contents

  1. Syntax
  2. Description
    1. IF EXISTS
  3. Examples
  4. See Also

Description

This statement is a variant of UNINSTALL PLUGIN statement, that removes all plugins belonging to a specified plugin_library. See UNINSTALL PLUGIN for details.

plugin_library is the name of the shared library that contains the plugin code. The file name extension (for example, libmyplugin.so or libmyplugin.dll) can be omitted (which makes the statement look the same on all architectures).

To use UNINSTALL SONAME, you must have the DELETE privilege for the mysql.plugin table.

MariaDB starting with 10.4.0

IF EXISTS

If the IF EXISTS clause is used, MariaDB will return a note instead of an error if the plugin library does not exist. See SHOW WARNINGS.

Examples

To uninstall the XtraDB plugin and all of its information_schema tables with one statement, use

UNINSTALL SONAME 'ha_xtradb';

From MariaDB 10.4.0:

UNINSTALL SONAME IF EXISTS 'ha_example';
Query OK, 0 rows affected (0.099 sec)

UNINSTALL SONAME IF EXISTS 'ha_example';
Query OK, 0 rows affected, 1 warning (0.000 sec)

SHOW WARNINGS;
+-------+------+-------------------------------------+
| Level | Code | Message                             |
+-------+------+-------------------------------------+
| Note  | 1305 | SONAME ha_example.so does not exist |
+-------+------+-------------------------------------+

See Also

1.1.1.2.6.7 mysql_plugin

1.1.1.2.7 SET Commands

There are 1 related questions.

1.1.1.2.7.1 SET

Syntax

SET variable_assignment [, variable_assignment] ...

variable_assignment:
      user_var_name = expr
    | [GLOBAL | SESSION] system_var_name = expr
    | [@@global. | @@session. | @@]system_var_name = expr

Contents

  1. Syntax
  2. Description
    1. GLOBAL / SESSION
    2. DEFAULT
  3. Examples
  4. See Also

One can also set a user variable in any expression with this syntax:

user_var_name:= expr

Description

The SET statement assigns values to different types of variables that affect the operation of the server or your client. Older versions of MySQL employed SET OPTION, but this syntax was deprecated in favor of SET without OPTION, and was removed in MariaDB 10.0.

Changing a system variable by using the SET statement does not make the change permanently. To do so, the change must be made in a configuration file.

For setting variables on a per-query basis, see SET STATEMENT.

See SHOW VARIABLES for documentation on viewing server system variables.

See Server System Variables for a list of all the system variables.

GLOBAL / SESSION

When setting a system variable, the scope can be specified as either GLOBAL or SESSION.

A global variable change affects all new sessions. It does not affect any currently open sessions, including the one that made the change.

A session variable change affects the current session only.

If the variable has a session value, not specifying either GLOBAL or SESSION will be the same as specifying SESSION. If the variable only has a global value, not specifying GLOBAL or SESSION will apply to the change to the global value.

DEFAULT

Setting a global variable to DEFAULT will restore it to the server default, and setting a session variable to DEFAULT will restore it to the current global value.

Examples

SELECT VARIABLE_NAME, SESSION_VALUE, GLOBAL_VALUE FROM
 INFORMATION_SCHEMA.SYSTEM_VARIABLES WHERE 
  VARIABLE_NAME IN ('max_error_count', 'skip_parallel_replication', 'innodb_sync_spin_loops');
+---------------------------+---------------+--------------+
| VARIABLE_NAME             | SESSION_VALUE | GLOBAL_VALUE |
+---------------------------+---------------+--------------+
| MAX_ERROR_COUNT           | 64            | 64           |
| SKIP_PARALLEL_REPLICATION | OFF           | NULL         |
| INNODB_SYNC_SPIN_LOOPS    | NULL          | 30           |
+---------------------------+---------------+--------------+

Setting the session values:

SET max_error_count=128;Query OK, 0 rows affected (0.000 sec)

SET skip_parallel_replication=ON;Query OK, 0 rows affected (0.000 sec)

SET innodb_sync_spin_loops=60;
ERROR 1229 (HY000): Variable 'innodb_sync_spin_loops' is a GLOBAL variable 
  and should be set with SET GLOBAL

SELECT VARIABLE_NAME, SESSION_VALUE, GLOBAL_VALUE FROM
 INFORMATION_SCHEMA.SYSTEM_VARIABLES WHERE 
  VARIABLE_NAME IN ('max_error_count', 'skip_parallel_replication', 'innodb_sync_spin_loops');
+---------------------------+---------------+--------------+
| VARIABLE_NAME             | SESSION_VALUE | GLOBAL_VALUE |
+---------------------------+---------------+--------------+
| MAX_ERROR_COUNT           | 128           | 64           |
| SKIP_PARALLEL_REPLICATION | ON            | NULL         |
| INNODB_SYNC_SPIN_LOOPS    | NULL          | 30           |
+---------------------------+---------------+--------------+

Setting the global values:

SET GLOBAL max_error_count=256;

SET GLOBAL skip_parallel_replication=ON;
ERROR 1228 (HY000): Variable 'skip_parallel_replication' is a SESSION variable 
  and can't be used with SET GLOBAL

SET GLOBAL innodb_sync_spin_loops=120;

SELECT VARIABLE_NAME, SESSION_VALUE, GLOBAL_VALUE FROM
 INFORMATION_SCHEMA.SYSTEM_VARIABLES WHERE 
  VARIABLE_NAME IN ('max_error_count', 'skip_parallel_replication', 'innodb_sync_spin_loops');
+---------------------------+---------------+--------------+
| VARIABLE_NAME             | SESSION_VALUE | GLOBAL_VALUE |
+---------------------------+---------------+--------------+
| MAX_ERROR_COUNT           | 128           | 256          |
| SKIP_PARALLEL_REPLICATION | ON            | NULL         |
| INNODB_SYNC_SPIN_LOOPS    | NULL          | 120          |
+---------------------------+---------------+--------------+

SHOW VARIABLES will by default return the session value unless the variable is global only.

SHOW VARIABLES LIKE 'max_error_count';
+-----------------+-------+
| Variable_name   | Value |
+-----------------+-------+
| max_error_count | 128   |
+-----------------+-------+

SHOW VARIABLES LIKE 'skip_parallel_replication';
+---------------------------+-------+
| Variable_name             | Value |
+---------------------------+-------+
| skip_parallel_replication | ON    |
+---------------------------+-------+

SHOW VARIABLES LIKE 'innodb_sync_spin_loops';
+------------------------+-------+
| Variable_name          | Value |
+------------------------+-------+
| innodb_sync_spin_loops | 120   |
+------------------------+-------+

Using the inplace syntax:

SELECT (@a:=1);
+---------+
| (@a:=1) |
+---------+
|       1 |
+---------+

SELECT @a;
+------+
| @a   |
+------+
|    1 |
+------+

See Also

1.1.1.2.7.2 SET CHARACTER SET

Syntax

SET {CHARACTER SET | CHARSET}
    {charset_name | DEFAULT}

Description

Sets the character_set_client and character_set_results session system variables to the specified character set and collation_connection to the value of collation_database, which implicitly sets character_set_connection to the value of character_set_database.

This maps all strings sent between the current client and the server with the given mapping.

Example

SHOW VARIABLES LIKE 'character_set\_%';
+--------------------------+--------+
| Variable_name            | Value  |
+--------------------------+--------+
| character_set_client     | utf8   |
| character_set_connection | utf8   |
| character_set_database   | latin1 |
| character_set_filesystem | binary |
| character_set_results    | utf8   |
| character_set_server     | latin1 |
| character_set_system     | utf8   |
+--------------------------+--------+

SHOW VARIABLES LIKE 'collation%';
+----------------------+-------------------+
| Variable_name        | Value             |
+----------------------+-------------------+
| collation_connection | utf8_general_ci   |
| collation_database   | latin1_swedish_ci |
| collation_server     | latin1_swedish_ci |
+----------------------+-------------------+

SET CHARACTER SET utf8mb4;

SHOW VARIABLES LIKE 'character_set\_%';
+--------------------------+---------+
| Variable_name            | Value   |
+--------------------------+---------+
| character_set_client     | utf8mb4 |
| character_set_connection | latin1  |
| character_set_database   | latin1  |
| character_set_filesystem | binary  |
| character_set_results    | utf8mb4 |
| character_set_server     | latin1  |
| character_set_system     | utf8    |
+--------------------------+---------+

SHOW VARIABLES LIKE 'collation%';
+----------------------+-------------------+
| Variable_name        | Value             |
+----------------------+-------------------+
| collation_connection | latin1_swedish_ci |
| collation_database   | latin1_swedish_ci |
| collation_server     | latin1_swedish_ci |
+----------------------+-------------------+

See Also

1.1.1.2.7.3 SET GLOBAL SQL_SLAVE_SKIP_COUNTER

1.1.1.2.7.4 SET NAMES

Syntax

SET NAMES {'charset_name'
    [COLLATE 'collation_name'] | DEFAULT}

Contents

  1. Syntax
  2. Description
  3. Examples
  4. See Also

Description

Sets the character_set_client, character_set_connection, character_set_results and, implicitly, the collation_connection session system variables to the specified character set and collation.

This determines which character set the client will use to send statements to the server, and the server will use for sending results back to the client.

ucs2, utf16, and utf32 are not valid character sets for SET NAMES, as they cannot be used as client character sets.

The collation clause is optional. If not defined (or if DEFAULT is specified), the default collation for the character set will be used.

Quotes are optional for the character set or collation clauses.

Examples

SELECT VARIABLE_NAME, SESSION_VALUE 
  FROM INFORMATION_SCHEMA.SYSTEM_VARIABLES WHERE 
  VARIABLE_NAME LIKE 'character_set_c%' OR 
  VARIABLE_NAME LIKE 'character_set_re%' OR 
  VARIABLE_NAME LIKE 'collation_c%';
+--------------------------+-----------------+
| VARIABLE_NAME            | SESSION_VALUE   |
+--------------------------+-----------------+
| CHARACTER_SET_RESULTS    | utf8            |
| CHARACTER_SET_CONNECTION | utf8            |
| CHARACTER_SET_CLIENT     | utf8            |
| COLLATION_CONNECTION     | utf8_general_ci |
+--------------------------+-----------------+

SET NAMES big5;

SELECT VARIABLE_NAME, SESSION_VALUE 
  FROM INFORMATION_SCHEMA.SYSTEM_VARIABLES WHERE 
  VARIABLE_NAME LIKE 'character_set_c%' OR 
  VARIABLE_NAME LIKE 'character_set_re%' OR 
  VARIABLE_NAME LIKE 'collation_c%';
+--------------------------+-----------------+
| VARIABLE_NAME            | SESSION_VALUE   |
+--------------------------+-----------------+
| CHARACTER_SET_RESULTS    | big5            |
| CHARACTER_SET_CONNECTION | big5            |
| CHARACTER_SET_CLIENT     | big5            |
| COLLATION_CONNECTION     | big5_chinese_ci |
+--------------------------+-----------------+

SET NAMES 'latin1' COLLATE 'latin1_bin';

SELECT VARIABLE_NAME, SESSION_VALUE 
  FROM INFORMATION_SCHEMA.SYSTEM_VARIABLES WHERE 
  VARIABLE_NAME LIKE 'character_set_c%' OR 
  VARIABLE_NAME LIKE 'character_set_re%' OR 
  VARIABLE_NAME LIKE 'collation_c%';
+--------------------------+---------------+
| VARIABLE_NAME            | SESSION_VALUE |
+--------------------------+---------------+
| CHARACTER_SET_RESULTS    | latin1        |
| CHARACTER_SET_CONNECTION | latin1        |
| CHARACTER_SET_CLIENT     | latin1        |
| COLLATION_CONNECTION     | latin1_bin    |
+--------------------------+---------------+

SET NAMES DEFAULT;

SELECT VARIABLE_NAME, SESSION_VALUE 
  FROM INFORMATION_SCHEMA.SYSTEM_VARIABLES WHERE 
  VARIABLE_NAME LIKE 'character_set_c%' OR 
  VARIABLE_NAME LIKE 'character_set_re%' OR 
  VARIABLE_NAME LIKE 'collation_c%';
+--------------------------+-------------------+
| VARIABLE_NAME            | SESSION_VALUE     |
+--------------------------+-------------------+
| CHARACTER_SET_RESULTS    | latin1            |
| CHARACTER_SET_CONNECTION | latin1            |
| CHARACTER_SET_CLIENT     | latin1            |
| COLLATION_CONNECTION     | latin1_swedish_ci |
+--------------------------+-------------------+

See Also

1.1.1.2.7.5 SET PASSWORD

1.1.1.2.7.6 SET ROLE

1.1.1.2.7.7 SET SQL_LOG_BIN

Syntax

SET [SESSION] sql_log_bin = {0|1}

Description

Sets the sql_log_bin system variable, which disables or enables binary logging for the current connection, if the client has the SUPER privilege. The statement is refused with an error if the client does not have that privilege.

Before MariaDB 5.5 and before MySQL 5.6 one could also set sql_log_bin as a global variable. This has now been disabled as this was too dangerous as it could damage replication.

1.1.1.2.7.8 SET STATEMENT

Contents

  1. Syntax
  2. Description
  3. Examples
  4. Limitations
  5. Source
MariaDB starting with 10.1.2

Per-query variables were introduced in MariaDB 10.1.2

SET STATEMENT can be used to set the value of a system variable for the duration of the statement. It is also possible to set multiple variables.

Syntax

SET STATEMENT var1=value1 [, var2=value2, ...] 
  FOR <statement>

where varN is a system variable (list of allowed variables is provided below), and valueN is a constant literal.

Description

SET STATEMENT var1=value1 FOR stmt

is roughly equivalent to

SET @save_value=@@var1;
SET SESSION var1=value1;
stmt;
SET SESSION var1=@save_value;

The server parses the whole statement before executing it, so any variables set in this fashion that affect the parser may not have the expected effect. Examples include the charset variables, sql_mode=ansi_quotes, etc.

Examples

One can limit statement execution time max_statement_time:

SET STATEMENT max_statement_time=1000 FOR SELECT ... ;

One can switch on/off individual optimizations:

SET STATEMENT optimizer_switch='materialization=off' FOR SELECT ....;

It is possible to enable MRR/BKA for a query: 

SET STATEMENT  join_cache_level=6, optimizer_switch='mrr=on'  FOR SELECT ...

Note that it makes no sense to try to set a session variable inside a SET STATEMENT:

#USELESS STATEMENT
SET STATEMENT sort_buffer_size = 100000 for SET SESSION sort_buffer_size = 200000;

For the above, after setting sort_buffer_size to 200000 it will be reset to its original state (the state before the SET STATEMENT started) after the statement execution.

Limitations

There are a number of variables that cannot be set on per-query basis. These include:

  • autocommit
  • character_set_client
  • character_set_connection
  • character_set_filesystem
  • collation_connection
  • default_master_connection
  • debug_sync
  • interactive_timeout
  • gtid_domain_id
  • last_insert_id
  • log_slow_filter
  • log_slow_rate_limit
  • log_slow_verbosity
  • long_query_time
  • min_examined_row_limit
  • profiling
  • profiling_history_size
  • query_cache_type
  • rand_seed1
  • rand_seed2
  • skip_replication
  • slow_query_log
  • sql_log_off
  • tx_isolation
  • wait_timeout

Source

  • The feature was originally implemented as a Google Summer of Code 2009 project by Joseph Lukas.
  • Percona Server 5.6 included it as Per-query variable statement
  • MariaDB ported the patch and fixed many bugs. The task in MariaDB Jira is MDEV-5231.

1.1.1.2.7.9 SET TRANSACTION

Syntax

SET [GLOBAL | SESSION] TRANSACTION
    transaction_property [, transaction_property] ...

transaction_property:
    ISOLATION LEVEL level
  | READ WRITE
  | READ ONLY

level:
     REPEATABLE READ
   | READ COMMITTED
   | READ UNCOMMITTED
   | SERIALIZABLE

Contents

  1. Syntax
  2. Description
    1. Isolation Level
    2. Isolation Levels
      1. READ UNCOMMITTED
      2. READ COMMITTED
      3. REPEATABLE READ
      4. SERIALIZABLE
    3. Access Mode
  3. Examples

Description

This statement sets the transaction isolation level or the transaction access mode globally, for the current session, or for the next transaction:

  • With the GLOBAL keyword, the statement sets the default transaction level globally for all subsequent sessions. Existing sessions are unaffected.
  • With the SESSION keyword, the statement sets the default transaction level for all subsequent transactions performed within the current session.
  • Without any SESSION or GLOBAL keyword, the statement sets the isolation level for the next (not started) transaction performed within the current session.

A change to the global default isolation level requires the SUPER privilege. Any session is free to change its session isolation level (even in the middle of a transaction), or the isolation level for its next transaction.

Isolation Level

To set the global default isolation level at server startup, use the --transaction-isolation=level option on the command line or in an option file. Values of level for this option use dashes rather than spaces, so the allowable values are READ-UNCOMMITTED, READ-COMMITTED, REPEATABLE-READ, or SERIALIZABLE. For example, to set the default isolation level to REPEATABLE READ, use these lines in the [mysqld] section of an option file:

[mysqld]
transaction-isolation = REPEATABLE-READ

To determine the global and session transaction isolation levels at runtime, check the value of the tx_isolation system variable:

SELECT @@GLOBAL.tx_isolation, @@tx_isolation;

InnoDB supports each of the translation isolation levels described here using different locking strategies. The default level is REPEATABLE READ. For additional information about InnoDB record-level locks and how it uses them to execute various types of statements, see InnoDB Lock Modes, and http://dev.mysql.com/doc/refman/en/innodb-locks-set.html.

Isolation Levels

The following sections describe how MariaDB supports the different transaction levels.

READ UNCOMMITTED

SELECT statements are performed in a non-locking fashion, but a possible earlier version of a row might be used. Thus, using this isolation level, such reads are not consistent. This is also called a "dirty read." Otherwise, this isolation level works like READ COMMITTED.

READ COMMITTED

A somewhat Oracle-like isolation level with respect to consistent (non-locking) reads: Each consistent read, even within the same transaction, sets and reads its own fresh snapshot. See http://dev.mysql.com/doc/refman/en/innodb-consistent-read.html.

For locking reads (SELECT with FOR UPDATE or LOCK IN SHARE MODE), InnoDB locks only index records, not the gaps before them, and thus allows the free insertion of new records next to locked records. For UPDATE and DELETE statements, locking depends on whether the statement uses a unique index with a unique search condition (such as WHERE id = 100), or a range-type search condition (such as WHERE id > 100). For a unique index with a unique search condition, InnoDB locks only the index record found, not the gap before it. For range-type searches, InnoDB locks the index range scanned, using gap locks or next-key (gap plus index-record) locks to block insertions by other sessions into the gaps covered by the range. This is necessary because "phantom rows" must be blocked for MySQL replication and recovery to work.

Note: If the READ COMMITTED isolation level is used or the innodb_locks_unsafe_for_binlog system variable is enabled, there is no InnoDB gap locking except for foreign-key constraint checking and duplicate-key checking. Also, record locks for non-matching rows are released after MariaDB has evaluated the WHERE condition.If you use READ COMMITTED or enable innodb_locks_unsafe_for_binlog, you must use row-based binary logging.

REPEATABLE READ

This is the default isolation level for InnoDB. For consistent reads, there is an important difference from the READ COMMITTED isolation level: All consistent reads within the same transaction read the snapshot established by the first read. This convention means that if you issue several plain (non-locking) SELECT statements within the same transaction, these SELECT statements are consistent also with respect to each other. See http://dev.mysql.com/doc/refman/en/innodb-consistent-read.html.

For locking reads (SELECT with FOR UPDATE or LOCK IN SHARE MODE), UPDATE, and DELETE statements, locking depends on whether the statement uses a unique index with a unique search condition, or a range-type search condition. For a unique index with a unique search condition, InnoDB locks only the index record found, not the gap before it. For other search conditions, InnoDB locks the index range scanned, using gap locks or next-key (gap plus index-record) locks to block insertions by other sessions into the gaps covered by the range.

This is the minimum isolation level for non-distributed XA transactions.

SERIALIZABLE

This level is like REPEATABLE READ, but InnoDB implicitly converts all plain SELECT statements to SELECT ... LOCK IN SHARE MODE if autocommit is disabled. If autocommit is enabled, the SELECT is its own transaction. It therefore is known to be read only and can be serialized if performed as a consistent (non-locking) read and need not block for other transactions. (This means that to force a plain SELECT to block if other transactions have modified the selected rows, you should disable autocommit.)

Distributed XA transactions should always use this isolation level.

Access Mode

The access mode specifies whether the transaction is allowed to write data or not. By default, transactions are in READ WRITE mode (see the tx_read_only system variable). READ ONLY mode allows the storage engine to apply optimizations that cannot be used for transactions which write data. The only exception to this rule is that read only transactions can perform DDL statements on temporary tables.

It is not permitted to specify both READ WRITE and READ ONLY in the same statement.

READ WRITE and READ ONLY can also be specified in the START TRANSACTION statement, in which case the specified mode is only valid for one transaction.

Examples

SET GLOBAL TRANSACTION ISOLATION LEVEL SERIALIZABLE;

Attempting to set the isolation level within an existing transaction without specifying GLOBAL or SESSION.

START TRANSACTION;

SET TRANSACTION ISOLATION LEVEL SERIALIZABLE;
ERROR 1568 (25001): Transaction characteristics can't be changed while a transaction is in progress

1.1.1.2.7.10 SET Variable

Syntax

SET var_name = expr [, var_name = expr] ...

Contents

  1. Syntax
  2. Description
  3. See Also

Description

The SET statement in stored programs is an extended version of the general SET statement. Referenced variables may be ones declared inside a stored program, global system variables, or user-defined variables.

The SET statement in stored programs is implemented as part of the pre-existing SET syntax. This allows an extended syntax of SET a=x, b=y, ... where different variable types (locally declared variables, global and session server variables, user-defined variables) can be mixed. This also allows combinations of local variables and some options that make sense only for system variables; in that case, the options are recognized but ignored.

SET can be used with both local variables and user-defined variables.

When setting several variables using the columns returned by a query, SELECT INTO should be preferred.

To set many variables to the same value, the LAST_VALUE( ) function can be used.

Below is an example of how a user-defined variable may be set:

SET @x = 1;

See Also

1.1.1.2.8 SHOW

Articles on the various SHOW commands.

1.1.1.2.8.1 About SHOW

SHOW has many forms that provide information about databases, tables, columns, or status information about the server. These include:

like_or_where:
    LIKE 'pattern'
  | WHERE expr

If the syntax for a given SHOW statement includes a LIKE 'pattern' part, 'pattern' is a string that can contain the SQL "%" and "_" wildcard characters. The pattern is useful for restricting statement output to matching values.

Several SHOW statements also accept a WHERE clause that provides more flexibility in specifying which rows to display. See Extended Show.

1.1.1.2.8.2 Extended Show

Contents

  1. Examples

The following SHOW statements can be extended by using a WHERE clause and a LIKE clause to refine the results:

As with a regular SELECT, the WHERE clause can be used for the specific columns returned, and the LIKE clause with the regular wildcards.

Examples

SHOW TABLES;
+----------------------+
| Tables_in_test       |
+----------------------+
| animal_count         |
| animals              |
| are_the_mooses_loose |
| aria_test2           |
| t1                   |
| view1                |
+----------------------+

Showing the tables beginning with a only.

SHOW TABLES WHERE Tables_in_test LIKE 'a%';
+----------------------+
| Tables_in_test       |
+----------------------+
| animal_count         |
| animals              |
| are_the_mooses_loose |
| aria_test2           |
+----------------------+

Variables whose name starts with aria and with a valued of greater than 8192:

SHOW VARIABLES WHERE Variable_name LIKE 'aria%' AND Value >8192;
+------------------------------+---------------------+
| Variable_name                | Value               |
+------------------------------+---------------------+
| aria_checkpoint_log_activity | 1048576             |
| aria_log_file_size           | 1073741824          |
| aria_max_sort_file_size      | 9223372036853727232 |
| aria_pagecache_buffer_size   | 134217728           |
| aria_sort_buffer_size        | 134217728           |
+------------------------------+---------------------+

Shortcut, just returning variables whose name begins with aria.

SHOW VARIABLES LIKE 'aria%';
+------------------------------------------+---------------------+
| Variable_name                            | Value               |
+------------------------------------------+---------------------+
| aria_block_size                          | 8192                |
| aria_checkpoint_interval                 | 30                  |
| aria_checkpoint_log_activity             | 1048576             |
| aria_force_start_after_recovery_failures | 0                   |
| aria_group_commit                        | none                |
| aria_group_commit_interval               | 0                   |
| aria_log_file_size                       | 1073741824          |
| aria_log_purge_type                      | immediate           |
| aria_max_sort_file_size                  | 9223372036853727232 |
| aria_page_checksum                       | ON                  |
| aria_pagecache_age_threshold             | 300                 |
| aria_pagecache_buffer_size               | 134217728           |
| aria_pagecache_division_limit            | 100                 |
| aria_recover                             | NORMAL              |
| aria_repair_threads                      | 1                   |
| aria_sort_buffer_size                    | 134217728           |
| aria_stats_method                        | nulls_unequal       |
| aria_sync_log_dir                        | NEWFILE             |
| aria_used_for_temp_tables                | ON                  |
+------------------------------------------+---------------------+

1.1.1.2.8.3 SHOW AUTHORS

Syntax

SHOW AUTHORS

Description

The SHOW AUTHORS statement displays information about the people who work on MariaDB. For each author, it displays Name, Location, and Comment values. All columns are encoded as latin1.

These include:

  • First the active people in MariaDB are listed.
  • Then the active people in MySQL.
  • Last the people that have contributed to MariaDB/MySQL in the past.

The order is somewhat related to importance of the contribution given to the MariaDB project, but this is not 100% accurate. There is still room for improvement and debate...

Example

SHOW AUTHORS;
+--------------------------------+---------------------------------------+-----------------------------------------------------------------------------------------------------------------------------------------+
| Name                           | Location                              | Comment                                                                                                                                 |
+--------------------------------+---------------------------------------+-----------------------------------------------------------------------------------------------------------------------------------------+
| Michael (Monty) Widenius       | Tusby, Finland                        | Lead developer and main author                                                                                                          |
| Sergei Golubchik               | Kerpen, Germany                       | Architect, Full-text search, precision math, plugin framework, merges etc                                                               |
| Igor Babaev                    | Bellevue, USA                         | Optimizer, keycache, core work                                                                                                          |
| Sergey Petrunia                | St. Petersburg, Russia                | Optimizer                                                                                                                               |
| Oleksandr Byelkin              | Lugansk, Ukraine                      | Query Cache (4.0), Subqueries (4.1), Views (5.0)                                                                                        |
| Timour Katchaounov             | Sofia , Bulgaria                      | Optimizer                                                                                                                               |
| Kristian Nielsen               | Copenhagen, Denmark                   | Replication, Async client prototocol, General buildbot stuff                                                                            |
| Alexander (Bar) Barkov         | Izhevsk, Russia                       | Unicode and character sets                                                                                                              |
| Alexey Botchkov (Holyfoot)     | Izhevsk, Russia                       | GIS extensions, embedded server, precision math                                                                                         |
| Daniel Bartholomew             | Raleigh, USA                          | MariaDB documentation                                                                                                                   |
| Colin Charles                  | Selangor, Malesia                     | MariaDB documentation, talks at a LOT of conferences                                                                                    |
| Sergey Vojtovich               | Izhevsk, Russia                       | initial implementation of plugin architecture, maintained native storage engines (MyISAM, MEMORY, ARCHIVE, etc), rewrite of table cache |
| Vladislav Vaintroub            | Mannheim, Germany                     | MariaDB Java connector, new thread pool, Windows optimizations                                                                          |
| Elena Stepanova                | Sankt Petersburg, Russia              | QA, test cases                                                                                                                          |
| Georg Richter                  | Heidelberg, Germany                   | New LGPL C connector, PHP connector                                                                                                     |
| Jan Lindström                  | Ylämylly, Finland                     | Working on InnoDB                                                                                                                       |
| Lixun Peng                     | Hangzhou, China                       | Multi Source replication                                                                                                                |
| Percona                        | CA, USA                               | XtraDB, microslow patches, extensions to slow log   
...

See Also

1.1.1.2.8.4 SHOW BINARY LOGS

Syntax

SHOW BINARY LOGS
SHOW MASTER LOGS

Description

Lists the binary log files on the server. This statement is used as part of the procedure described in PURGE BINARY LOGS, that shows how to determine which logs can be purged.

This statement requires the SUPER privilege, the REPLICATION_CLIENT privilege, or, from MariaDB 10.5.2, the BINLOG MONITOR privilege.

Examples

SHOW BINARY LOGS;
+--------------------+-----------+
| Log_name           | File_size |
+--------------------+-----------+
| mariadb-bin.000001 |     19039 |
| mariadb-bin.000002 |    717389 |
| mariadb-bin.000003 |       300 |
| mariadb-bin.000004 |       333 |
| mariadb-bin.000005 |       899 |
| mariadb-bin.000006 |       125 |
| mariadb-bin.000007 |     18907 |
| mariadb-bin.000008 |     19530 |
| mariadb-bin.000009 |       151 |
| mariadb-bin.000010 |       151 |
| mariadb-bin.000011 |       125 |
| mariadb-bin.000012 |       151 |
| mariadb-bin.000013 |       151 |
| mariadb-bin.000014 |       125 |
| mariadb-bin.000015 |       151 |
| mariadb-bin.000016 |       314 |
+--------------------+-----------+

1.1.1.2.8.5 SHOW BINLOG EVENTS

Syntax

SHOW BINLOG EVENTS
   [IN 'log_name'] [FROM pos] [LIMIT [offset,] row_count]

Description

Shows the events in the binary log. If you do not specify 'log_name', the first binary log is displayed.

Requires the BINLOG MONITOR privilege (>= MariaDB 10.5.2) or the REPLICATION SLAVE privilege (<= MariaDB 10.5.1).

Example

SHOW BINLOG EVENTS IN 'mysql_sandbox10019-bin.000002';
+-------------------------------+-----+-------------------+-----------+-------------+------------------------------------------------+
| Log_name                      | Pos | Event_type        | Server_id | End_log_pos | Info                                           |
+-------------------------------+-----+-------------------+-----------+-------------+------------------------------------------------+
| mysql_sandbox10019-bin.000002 |   4 | Format_desc       |         1 |         248 | Server ver: 10.0.19-MariaDB-log, Binlog ver: 4 |
| mysql_sandbox10019-bin.000002 | 248 | Gtid_list         |         1 |         273 | []                                             |
| mysql_sandbox10019-bin.000002 | 273 | Binlog_checkpoint |         1 |         325 | mysql_sandbox10019-bin.000002                  |
| mysql_sandbox10019-bin.000002 | 325 | Gtid              |         1 |         363 | GTID 0-1-1                                     |
| mysql_sandbox10019-bin.000002 | 363 | Query             |         1 |         446 | CREATE DATABASE blog                           |
| mysql_sandbox10019-bin.000002 | 446 | Gtid              |         1 |         484 | GTID 0-1-2                                     |
| mysql_sandbox10019-bin.000002 | 484 | Query             |         1 |         571 | use `blog`; CREATE TABLE bb (id INT)           |
+-------------------------------+-----+-------------------+-----------+-------------+------------------------------------------------+

1.1.1.2.8.6 SHOW CHARACTER SET

Syntax

SHOW CHARACTER SET
    [LIKE 'pattern' | WHERE expr]

Contents

  1. Syntax
  2. Description
  3. Examples
  4. See Also

Description

The SHOW CHARACTER SET statement shows all available character sets. The LIKE clause, if present on its own, indicates which character set names to match. The WHERE and LIKE clauses can be given to select rows using more general conditions, as discussed in Extended SHOW.

The same information can be queried from the Information Schema CHARACTER_SETS table.

See Setting Character Sets and Collations for details on specifying the character set at the server, database, table and column levels.

Examples

SHOW CHARACTER SET LIKE 'latin%';
+---------+-----------------------------+-------------------+--------+
| Charset | Description                 | Default collation | Maxlen |
+---------+-----------------------------+-------------------+--------+
| latin1  | cp1252 West European        | latin1_swedish_ci |      1 |
| latin2  | ISO 8859-2 Central European | latin2_general_ci |      1 |
| latin5  | ISO 8859-9 Turkish          | latin5_turkish_ci |      1 |
| latin7  | ISO 8859-13 Baltic          | latin7_general_ci |      1 |
+---------+-----------------------------+-------------------+--------+

SHOW CHARACTER SET WHERE Maxlen LIKE '2';
+---------+---------------------------+-------------------+--------+
| Charset | Description               | Default collation | Maxlen |
+---------+---------------------------+-------------------+--------+
| big5    | Big5 Traditional Chinese  | big5_chinese_ci   |      2 |
| sjis    | Shift-JIS Japanese        | sjis_japanese_ci  |      2 |
| euckr   | EUC-KR Korean             | euckr_korean_ci   |      2 |
| gb2312  | GB2312 Simplified Chinese | gb2312_chinese_ci |      2 |
| gbk     | GBK Simplified Chinese    | gbk_chinese_ci    |      2 |
| ucs2    | UCS-2 Unicode             | ucs2_general_ci   |      2 |
| cp932   | SJIS for Windows Japanese | cp932_japanese_ci |      2 |
+---------+---------------------------+-------------------+--------+

See Also

1.1.1.2.8.7 SHOW CLIENT_STATISTICS

Syntax

SHOW CLIENT_STATISTICS

Description

The SHOW CLIENT_STATISTICS statement is part of the User Statistics feature. It was removed as a separate statement in MariaDB 10.1.1, but effectively replaced by the generic SHOW information_schema_table statement. The information_schema.CLIENT_STATISTICS table holds statistics about client connections.

The userstat system variable must be set to 1 to activate this feature. See the User Statistics and information_schema.CLIENT_STATISTICS articles for more information.

Example

SHOW CLIENT_STATISTICS\G
*************************** 1. row ***************************
                Client: localhost
     Total_connections: 35
Concurrent_connections: 0
        Connected_time: 708
             Busy_time: 2.5557979999999985
              Cpu_time: 0.04123740000000002
        Bytes_received: 3883
            Bytes_sent: 21595
  Binlog_bytes_written: 0
             Rows_read: 18
             Rows_sent: 115
          Rows_deleted: 0
         Rows_inserted: 0
          Rows_updated: 0
       Select_commands: 70
       Update_commands: 0
        Other_commands: 0
   Commit_transactions: 1
 Rollback_transactions: 0
    Denied_connections: 0
      Lost_connections: 0
         Access_denied: 0
         Empty_queries: 35

1.1.1.2.8.8 SHOW COLUMNS

1.1.1.2.8.9 SHOW CONTRIBUTORS

Syntax

SHOW CONTRIBUTORS

Description

The SHOW CONTRIBUTORS statement displays information about the companies and people who financially contribute to MariaDB. For each contributor, it displays Name, Location, and Comment values. All columns are encoded as latin1.

It displays all members and sponsors of the MariaDB Foundation as well as other financial contributors.

Example

SHOW CONTRIBUTORS;
+---------------------+-------------------------------+-------------------------------------------------------------+
| Name                | Location                      | Comment                                                     |
+---------------------+-------------------------------+-------------------------------------------------------------+
| Booking.com         | https://www.booking.com       | Founding member, Platinum Sponsor of the MariaDB Foundation |
| Alibaba Cloud       | https://www.alibabacloud.com/ | Platinum Sponsor of the MariaDB Foundation                  |
| Tencent Cloud       | https://cloud.tencent.com     | Platinum Sponsor of the MariaDB Foundation                  |
| Microsoft           | https://microsoft.com/        | Platinum Sponsor of the MariaDB Foundation                  |
| MariaDB Corporation | https://mariadb.com           | Founding member, Platinum Sponsor of the MariaDB Foundation |
| Visma               | https://visma.com             | Gold Sponsor of the MariaDB Foundation                      |
| DBS                 | https://dbs.com               | Gold Sponsor of the MariaDB Foundation                      |
| IBM                 | https://www.ibm.com           | Gold Sponsor of the MariaDB Foundation                      |
| Tencent Games       | http://game.qq.com/           | Gold Sponsor of the MariaDB Foundation                      |
| Nexedi              | https://www.nexedi.com        | Silver Sponsor of the MariaDB Foundation                    |
| Acronis             | https://www.acronis.com       | Silver Sponsor of the MariaDB Foundation                    |
| Verkkokauppa.com    | https://www.verkkokauppa.com  | Bronze Sponsor of the MariaDB Foundation                    |
| Virtuozzo           | https://virtuozzo.com         | Bronze Sponsor of the MariaDB Foundation                    |
| Tencent Game DBA    | http://tencentdba.com/about   | Bronze Sponsor of the MariaDB Foundation                    |
| Tencent TDSQL       | http://tdsql.org              | Bronze Sponsor of the MariaDB Foundation                    |
| Percona             | https://www.percona.com/      | Bronze Sponsor of the MariaDB Foundation                    |
| Google              | USA                           | Sponsoring encryption, parallel replication and GTID        |
| Facebook            | USA                           | Sponsoring non-blocking API, LIMIT ROWS EXAMINED etc        |
| Ronald Bradford     | Brisbane, Australia           | EFF contribution for UC2006 Auction                         |
| Sheeri Kritzer      | Boston, Mass. USA             | EFF contribution for UC2006 Auction                         |
| Mark Shuttleworth   | London, UK.                   | EFF contribution for UC2006 Auction                         |
+---------------------+-------------------------------+-------------------------------------------------------------+

See Also

1.1.1.2.8.10 SHOW CREATE DATABASE

Syntax

SHOW CREATE {DATABASE | SCHEMA} db_name

Contents

  1. Syntax
  2. Description
  3. Examples
  4. See Also

Description

Shows the CREATE DATABASE statement that creates the given database. SHOW CREATE SCHEMA is a synonym for SHOW CREATE DATABASE. SHOW CREATE DATABASE quotes database names according to the value of the sql_quote_show_create server system variable.

Examples

SHOW CREATE DATABASE test;
+----------+-----------------------------------------------------------------+
| Database | Create Database                                                 |
+----------+-----------------------------------------------------------------+
| test     | CREATE DATABASE `test` /*!40100 DEFAULT CHARACTER SET latin1 */ |
+----------+-----------------------------------------------------------------+

SHOW CREATE SCHEMA test;
+----------+-----------------------------------------------------------------+
| Database | Create Database                                                 |
+----------+-----------------------------------------------------------------+
| test     | CREATE DATABASE `test` /*!40100 DEFAULT CHARACTER SET latin1 */ |
+----------+-----------------------------------------------------------------+

With sql_quote_show_create off:

SHOW CREATE DATABASE test;
+----------+---------------------------------------------------------------+
| Database | Create Database                                               |
+----------+---------------------------------------------------------------+
| test     | CREATE DATABASE test /*!40100 DEFAULT CHARACTER SET latin1 */ |
+----------+---------------------------------------------------------------+

With a comment, from MariaDB 10.5:

SHOW CREATE DATABASE p;
+----------+--------------------------------------------------------------------------------------+
| Database | Create Database                                                                      |
+----------+--------------------------------------------------------------------------------------+
| p        | CREATE DATABASE `p` /*!40100 DEFAULT CHARACTER SET latin1 */ COMMENT 'presentations' |
+----------+--------------------------------------------------------------------------------------+

See Also

1.1.1.2.8.11 SHOW CREATE EVENT

Syntax

SHOW CREATE EVENT event_name

Description

This statement displays the CREATE EVENT statement needed to re-create a given event, as well as the SQL_MODE that was used when the trigger has been created and the character set used by the connection. To find out which events are present, use SHOW EVENTS.

The output of this statement is unreliably affected by the sql_quote_show_create server system variable - see http://bugs.mysql.com/bug.php?id=12719

The information_schema.EVENTS table provides similar, but more complete, information.

Examples

SHOW CREATE EVENT test.e_daily\G
*************************** 1. row ***************************
               Event: e_daily
            sql_mode: 
           time_zone: SYSTEM
        Create Event: CREATE EVENT `e_daily`
                        ON SCHEDULE EVERY 1 DAY
                        STARTS CURRENT_TIMESTAMP + INTERVAL 6 HOUR
                        ON COMPLETION NOT PRESERVE
                        ENABLE
                        COMMENT 'Saves total number of sessions then
                                clears the table each day'
                        DO BEGIN
                          INSERT INTO site_activity.totals (time, total)
                            SELECT CURRENT_TIMESTAMP, COUNT(*) 
                            FROM site_activity.sessions;
                          DELETE FROM site_activity.sessions;
                        END
character_set_client: latin1
collation_connection: latin1_swedish_ci
  Database Collation: latin1_swedish_ci

See also

1.1.1.2.8.12 SHOW CREATE FUNCTION

Syntax

SHOW CREATE FUNCTION func_name

Description

This statement is similar to SHOW CREATE PROCEDURE but for stored functions.

The output of this statement is unreliably affected by the sql_quote_show_create server system variable - see http://bugs.mysql.com/bug.php?id=12719

Example

MariaDB [test]> SHOW CREATE FUNCTION VatCents\G
*************************** 1. row ***************************
            Function: VatCents
            sql_mode: 
     Create Function: CREATE DEFINER=`root`@`localhost` FUNCTION `VatCents`(price DECIMAL(10,2)) RETURNS int(11)
    DETERMINISTIC
BEGIN
 DECLARE x INT;
 SET x = price * 114;
 RETURN x;
END
character_set_client: utf8
collation_connection: utf8_general_ci
  Database Collation: latin1_swedish_ci

See also:

1.1.1.2.8.13 SHOW CREATE PACKAGE

MariaDB starting with 10.3.5

Oracle-style packages were introduced in MariaDB 10.3.5.

Syntax

SHOW CREATE PACKAGE  [ db_name . ] package_name

Contents

  1. Syntax
  2. Description
  3. Examples
  4. See Also

Description

The SHOW CREATE PACKAGE statement can be used when Oracle SQL_MODE is set.

Shows the CREATE statement that creates the given package specification.

Examples

SHOW CREATE PACKAGE employee_tools\G
*************************** 1. row ***************************
             Package: employee_tools
            sql_mode: PIPES_AS_CONCAT,ANSI_QUOTES,IGNORE_SPACE,ORACLE,NO_KEY_OPTIONS,NO_TABLE_OPTIONS,NO_FIELD_OPTIONS,NO_AUTO_CREATE_USER
      Create Package: CREATE DEFINER="root"@"localhost" PACKAGE "employee_tools" AS
  FUNCTION getSalary(eid INT) RETURN DECIMAL(10,2);
  PROCEDURE raiseSalary(eid INT, amount DECIMAL(10,2));
  PROCEDURE raiseSalaryStd(eid INT);
  PROCEDURE hire(ename TEXT, esalary DECIMAL(10,2));
END
character_set_client: utf8
collation_connection: utf8_general_ci
  Database Collation: latin1_swedish_ci

See Also

1.1.1.2.8.14 SHOW CREATE PACKAGE BODY

MariaDB starting with 10.3.5

Oracle-style packages were introduced in MariaDB 10.3.5.

Syntax

SHOW CREATE PACKAGE BODY  [ db_name . ] package_name

Contents

  1. Syntax
  2. Description
  3. Examples
  4. See also

Description

The SHOW CREATE PACKAGE BODY statement can be used when Oracle SQL_MODE is set.

Shows the CREATE statement that creates the given package body (i.e. the implementation).

Examples

SHOW CREATE PACKAGE BODY employee_tools\G
*************************** 1. row ***************************
        Package body: employee_tools
            sql_mode: PIPES_AS_CONCAT,ANSI_QUOTES,IGNORE_SPACE,ORACLE,NO_KEY_OPTIONS,NO_TABLE_OPTIONS,NO_FIELD_OPTIONS,NO_AUTO_CREATE_USER
 Create Package Body: CREATE DEFINER="root"@"localhost" PACKAGE BODY "employee_tools" AS
  
  stdRaiseAmount DECIMAL(10,2):=500;
  
  PROCEDURE log (eid INT, ecmnt TEXT) AS
  BEGIN
    INSERT INTO employee_log (id, cmnt) VALUES (eid, ecmnt);
  END;
  
  PROCEDURE hire(ename TEXT, esalary DECIMAL(10,2)) AS
    eid INT;
  BEGIN
    INSERT INTO employee (name, salary) VALUES (ename, esalary);
    eid:= last_insert_id();
    log(eid, 'hire ' || ename);
  END;

  FUNCTION getSalary(eid INT) RETURN DECIMAL(10,2) AS
    nSalary DECIMAL(10,2);
  BEGIN
    SELECT salary INTO nSalary FROM employee WHERE id=eid;
    log(eid, 'getSalary id=' || eid || ' salary=' || nSalary);
    RETURN nSalary;
  END;

  PROCEDURE raiseSalary(eid INT, amount DECIMAL(10,2)) AS
  BEGIN
    UPDATE employee SET salary=salary+amount WHERE id=eid;
    log(eid, 'raiseSalary id=' || eid || ' amount=' || amount);
  END;

  PROCEDURE raiseSalaryStd(eid INT) AS
  BEGIN
    raiseSalary(eid, stdRaiseAmount);
    log(eid, 'raiseSalaryStd id=' || eid);
  END;

BEGIN  
  log(0, 'Session ' || connection_id() || ' ' || current_user || ' started');
END
character_set_client: utf8
collation_connection: utf8_general_ci
  Database Collation: latin1_swedish_ci

See also

1.1.1.2.8.15 SHOW CREATE PROCEDURE

Syntax

SHOW CREATE PROCEDURE proc_name

Contents

  1. Syntax
  2. Description
  3. Examples
  4. See Also

Description

This statement is a MariaDB extension. It returns the exact string that can be used to re-create the named stored procedure, as well as the SQL_MODE that was used when the trigger has been created and the character set used by the connection.. A similar statement, SHOW CREATE FUNCTION, displays information about stored functions.

Both statements require that you are the owner of the routine or have the SELECT privilege on the mysql.proc table. When neither is true, the statements display NULL for the Create Procedure or Create Function field.

Warning Users with SELECT privileges on mysql.proc or USAGE privileges on *.* can view the text of routines, even when they do not have privileges for the function or procedure itself.

The output of these statements is unreliably affected by the sql_quote_show_create server system variable - see http://bugs.mysql.com/bug.php?id=12719

Examples

Here's a comparison of the SHOW CREATE PROCEDURE and SHOW CREATE FUNCTION statements.

SHOW CREATE PROCEDURE test.simpleproc\G
*************************** 1. row ***************************
           Procedure: simpleproc
            sql_mode: 
    Create Procedure: CREATE PROCEDURE `simpleproc`(OUT param1 INT)
                      BEGIN
                      SELECT COUNT(*) INTO param1 FROM t;
                      END
character_set_client: latin1
collation_connection: latin1_swedish_ci
  Database Collation: latin1_swedish_ci

SHOW CREATE FUNCTION test.hello\G
*************************** 1. row ***************************
            Function: hello
            sql_mode:
     Create Function: CREATE FUNCTION `hello`(s CHAR(20))
                      RETURNS CHAR(50)
                      RETURN CONCAT('Hello, ',s,'!')
character_set_client: latin1
collation_connection: latin1_swedish_ci
  Database Collation: latin1_swedish_ci

When the user issuing the statement does not have privileges on the routine, attempting to CALL the procedure raises Error 1370.

CALL test.prc1();
Error 1370 (42000): execute command denieed to user 'test_user'@'localhost' for routine 'test'.'prc1'

If the user neither has privilege to the routine nor the SELECT privilege on mysql.proc table, it raises Error 1305, informing them that the procedure does not exist.

SHOW CREATE TABLES test.prc1\G
Error 1305 (42000): PROCEDURE prc1 does not exist

See Also

1.1.1.2.8.16 SHOW CREATE SEQUENCE

MariaDB starting with 10.3.1

Sequences were introduced in MariaDB 10.3.

Syntax

SHOW CREATE SEQUENCE sequence_name;

Contents

  1. Syntax
  2. Description
  3. Example
  4. Notes
  5. See Also

Description

Shows the CREATE SEQUENCE statement that created the given sequence. The statement requires the SELECT privilege for the table.

Example

CREATE SEQUENCE s1 START WITH 50;
SHOW CREATE SEQUENCE s1\G;
*************************** 1. row ***************************
       Table: s1
Create Table: CREATE SEQUENCE `s1` start with 50 minvalue 1 maxvalue 9223372036854775806 
  increment by 1 cache 1000 nocycle ENGINE=InnoDB

Notes

If you want to see the underlying table structure used for the SEQUENCE you can use SHOW CREATE TABLE on the SEQUENCE. You can also use SELECT to read the current recorded state of the SEQUENCE:

SHOW CREATE TABLE s1\G
*************************** 1. row ***************************
       Table: s1
Create Table: CREATE TABLE `s1` (
  `next_not_cached_value` bigint(21) NOT NULL,
  `minimum_value` bigint(21) NOT NULL,
  `maximum_value` bigint(21) NOT NULL,
  `start_value` bigint(21) NOT NULL COMMENT 'start value when sequences is created 
     or value if RESTART is used',
  `increment` bigint(21) NOT NULL COMMENT 'increment value',
  `cache_size` bigint(21) unsigned NOT NULL,
  `cycle_option` tinyint(1) unsigned NOT NULL COMMENT '0 if no cycles are allowed, 
     1 if the sequence should begin a new cycle when maximum_value is passed',
  `cycle_count` bigint(21) NOT NULL COMMENT 'How many cycles have been done'
) ENGINE=InnoDB SEQUENCE=1

SELECT * FROM s1\G
*************************** 1. row ***************************
next_not_cached_value: 50
        minimum_value: 1
        maximum_value: 9223372036854775806
          start_value: 50
            increment: 1
           cache_size: 1000
         cycle_option: 0
          cycle_count: 0

See Also

1.1.1.2.8.17 SHOW CREATE TABLE

1.1.1.2.8.18 SHOW CREATE TRIGGER

Syntax

SHOW CREATE TRIGGER trigger_name

Contents

  1. Syntax
  2. Description
  3. Examples
  4. See also

Description

This statement shows a CREATE TRIGGER statement that creates the given trigger, as well as the SQL_MODE that was used when the trigger has been created and the character set used by the connection.

The output of this statement is unreliably affected by the sql_quote_show_create server system variable - see http://bugs.mysql.com/bug.php?id=12719

Examples

SHOW CREATE TRIGGER example\G
*************************** 1. row ***************************
               Trigger: example
              sql_mode: ONLY_FULL_GROUP_BY,STRICT_TRANS_TABLES,STRICT_ALL_TABLES
,NO_ZERO_IN_DATE,NO_ZERO_DATE,ERROR_FOR_DIVISION_BY_ZERO,NO_AUTO_CREATE_USER,NO_
ENGINE_SUBSTITUTION
SQL Original Statement: CREATE DEFINER=`root`@`localhost` TRIGGER example BEFORE
 INSERT ON t FOR EACH ROW
BEGIN
        SET NEW.c = NEW.c * 2;
END
  character_set_client: cp850
  collation_connection: cp850_general_ci
  Database Collation: utf8_general_ci
  Created: 2016-09-29 13:53:34.35
MariaDB starting with 10.2.3

The Created column was added in MySQL 5.7 and MariaDB 10.2.3 as part of introducing multiple trigger events per action.

See also

1.1.1.2.8.19 SHOW CREATE USER

1.1.1.2.8.20 SHOW CREATE VIEW

Syntax

SHOW CREATE VIEW view_name

Description

This statement shows a CREATE VIEW statement that creates the given view, as well as the character set used by the connection when the view was created. This statement also works with views.

SHOW CREATE VIEW quotes table, column and stored function names according to the value of the sql_quote_show_create server system variable.

Examples

SHOW CREATE VIEW example\G
*************************** 1. row ***************************
                View: example
         Create View: CREATE ALGORITHM=UNDEFINED DEFINER=`root`@`localhost` SQL
SECURITY DEFINER VIEW `example` AS (select `t`.`id` AS `id`,`t`.`s` AS `s` from
`t`)
character_set_client: cp850
collation_connection: cp850_general_ci

With sql_quote_show_create off:

SHOW CREATE VIEW example\G
*************************** 1. row ***************************
                View: example
         Create View: CREATE ALGORITHM=UNDEFINED DEFINER=root@localhost SQL SECU
RITY DEFINER VIEW example AS (select t.id AS id,t.s AS s from t)
character_set_client: cp850
collation_connection: cp850_general_ci

Grants

To be able to see a view, you need to have the SHOW VIEW and the SELECT privilege on the view:

GRANT SHOW VIEW,SELECT ON test_database.test_view TO 'test'@'localhost';

See Also

1.1.1.2.8.21 SHOW DATABASES

Syntax

SHOW {DATABASES | SCHEMAS}
    [LIKE 'pattern' | WHERE expr]

Contents

  1. Syntax
  2. Description
  3. Examples
  4. See Also

Description

SHOW DATABASES lists the databases on the MariaDB server host. SHOW SCHEMAS is a synonym for SHOW DATABASES. The LIKE clause, if present on its own, indicates which database names to match. The WHERE and LIKE clauses can be given to select rows using more general conditions, as discussed in Extended SHOW.

You see only those databases for which you have some kind of privilege, unless you have the global SHOW DATABASES privilege. You can also get this list using the mysqlshow command.

If the server was started with the --skip-show-database option, you cannot use this statement at all unless you have the SHOW DATABASES privilege.

The list of results returned by SHOW DATABASES is based on directories in the data directory, which is how MariaDB implements databases. It's possible that output includes directories that do not correspond to actual databases.

The Information Schema SCHEMATA table also contains database information.

Examples

SHOW DATABASES;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| mysql              |
| performance_schema |
| test               |
+--------------------+

SHOW DATABASES LIKE 'm%';
+---------------+
| Database (m%) |
+---------------+
| mysql         |
+---------------+

See Also

1.1.1.2.8.22 SHOW ENGINE

Contents

  1. Syntax
  2. Description
    1. SHOW ENGINE INNODB STATUS
    2. SHOW ENGINE INNODB MUTEX
    3. SHOW ENGINE PERFORMANCE_SCHEMA STATUS
    4. SHOW ENGINE ROCKSDB STATUS

Syntax

SHOW ENGINE engine_name {STATUS | MUTEX}

Description

SHOW ENGINE displays operational information about a storage engine. The following statements currently are supported:

SHOW ENGINE INNODB STATUS
SHOW ENGINE INNODB MUTEX
SHOW ENGINE PERFORMANCE_SCHEMA STATUS
SHOW ENGINE ROCKSDB STATUS

If the Sphinx Storage Engine is installed, the following is also supported:

SHOW ENGINE SPHINX STATUS

See SHOW ENGINE SPHINX STATUS.

Older (and now removed) synonyms were SHOW INNODB STATUS for SHOW ENGINE INNODB STATUS and SHOW MUTEX STATUS for SHOW ENGINE INNODB MUTEX.

SHOW ENGINE INNODB STATUS

SHOW ENGINE INNODB STATUS displays extensive information from the standard InnoDB Monitor about the state of the InnoDB storage engine. See SHOW ENGINE INNODB STATUS for more.

SHOW ENGINE INNODB MUTEX

SHOW ENGINE INNODB MUTEX displays InnoDB mutex statistics.

The statement displays the following output fields:

  • Type: Always InnoDB.
  • Name: The source file where the mutex is implemented, and the line number in the file where the mutex is created. The line number is dependent on the MariaDB version.
  • Status: This field displays the following values if UNIV_DEBUG was defined at compilation time (for example, in include/univ.h in the InnoDB part of the source tree). Only the os_waits value is displayed if UNIV_DEBUG was not defined. Without UNIV_DEBUG, the information on which the output is based is insufficient to distinguish regular mutexes and mutexes that protect rw-locks (which allow multiple readers or a single writer). Consequently, the output may appear to contain multiple rows for the same mutex.
    • count indicates how many times the mutex was requested.
    • spin_waits indicates how many times the spinlock had to run.
    • spin_rounds indicates the number of spinlock rounds. (spin_rounds divided by spin_waits provides the average round count.)
    • os_waits indicates the number of operating system waits. This occurs when the spinlock did not work (the mutex was not locked during the spinlock and it was necessary to yield to the operating system and wait).
    • os_yields indicates the number of times a the thread trying to lock a mutex gave up its timeslice and yielded to the operating system (on the presumption that allowing other threads to run will free the mutex so that it can be locked).
    • os_wait_times indicates the amount of time (in ms) spent in operating system waits, if the timed_mutexes system variable is 1 (ON). If timed_mutexes is 0 (OFF), timing is disabled, so os_wait_times is 0. timed_mutexes is off by default.

Information from this statement can be used to diagnose system problems. For example, large values of spin_waits and spin_rounds may indicate scalability problems.

The information_schema.INNODB_MUTEXES table provides similar information.

SHOW ENGINE PERFORMANCE_SCHEMA STATUS

This statement shows how much memory is used for performance_schema tables and internal buffers.

The output contains the following fields:

  • Type: Always performance_schema.
  • Name: The name of a table, the name of an internal buffer, or the performance_schema word, followed by a dot and an attribute. Internal buffers names are enclosed by parenthesis. performance_schema means that the attribute refers to the whole database (it is a total).
  • Status: The value for the attribute.

The following attributes are shown, in this order, for all tables:

  • row_size: The memory used for an individual record. This value will never change.
  • row_count: The number of rows in the table or buffer. For some tables, this value depends on a server system variable.
  • memory: For tables and performance_schema, this is the result of row_size * row_count.

For internal buffers, the attributes are:

  • count
  • size

SHOW ENGINE ROCKSDB STATUS

See also MyRocks Performance Troubleshooting

1.1.1.2.8.23 SHOW ENGINE INNODB STATUS

SHOW ENGINE INNODB STATUS is a specific form of the SHOW ENGINE statement that displays the InnoDB Monitor output, which is extensive InnoDB information which can be useful in diagnosing problems.

The following sections are displayed

  • Status: Shows the timestamp, monitor name and the number of seconds, or the elapsed time between the current time and the time the InnoDB Monitor output was last displayed. The per-second averages are based upon this time.
  • BACKGROUND THREAD: srv_master_thread lines show work performed by the main background thread.
  • SEMAPHORES: Threads waiting for a semaphore and stats on how the number of times threads have needed a spin or a wait on a mutex or rw-lock semaphore. If this number of threads is large, there may be I/O or contention issues. Reducing the size of the innodb_thread_concurrency system variable may help if contention is related to thread scheduling. Spin rounds per wait shows the number of spinlock rounds per OS wait for a mutex.
  • LATEST FOREIGN KEY ERROR: Only shown if there has been a foreign key constraint error, it displays the failed statement and information about the constraint and the related tables.
  • LATEST DETECTED DEADLOCK: Only shown if there has been a deadlock, it displays the transactions involved in the deadlock and the statements being executed, held and required locked and the transaction rolled back to.
  • TRANSACTIONS: The output of this section can help identify lock contention, as well as reasons for the deadlocks.
  • FILE I/O: InnoDB thread information as well as pending I/O operations and I/O performance statistics.
  • INSERT BUFFER AND ADAPTIVE HASH INDEX: InnoDB insert buffer (old name for the change buffer) and adaptive hash index status information, including the number of each type of operation performed, and adaptive hash index performance.
  • LOG: InnoDB log information, including current log sequence number, how far the log has been flushed to disk, the position at which InnoDB last took a checkpoint, pending writes and write performance statistics.
  • BUFFER POOL AND MEMORY: Information on buffer pool pages read and written, which allows you to see the number of data file I/O operations performed by your queries. See InnoDB Buffer Pool for more. Similar information is also available from the INFORMATION_SCHEMA.INNODB_BUFFER_POOL_STATS table.
  • ROW OPERATIONS:Information about the main thread, including the number and performance rate for each type of row operation.

If the innodb_status_output_locks system variable is set to 1, extended lock information will be displayed.

Example output:

=====================================
2019-09-06 12:44:13 0x7f93cc236700 INNODB MONITOR OUTPUT
=====================================
Per second averages calculated from the last 4 seconds
-----------------
BACKGROUND THREAD
-----------------
srv_master_thread loops: 2 srv_active, 0 srv_shutdown, 83698 srv_idle
srv_master_thread log flush and writes: 83682
----------
SEMAPHORES
----------
OS WAIT ARRAY INFO: reservation count 15
OS WAIT ARRAY INFO: signal count 8
RW-shared spins 0, rounds 20, OS waits 7
RW-excl spins 0, rounds 0, OS waits 0
RW-sx spins 0, rounds 0, OS waits 0
Spin rounds per wait: 20.00 RW-shared, 0.00 RW-excl, 0.00 RW-sx
------------
TRANSACTIONS
------------
Trx id counter 236
Purge done for trx's n:o < 236 undo n:o < 0 state: running
History list length 22
LIST OF TRANSACTIONS FOR EACH SESSION:
---TRANSACTION 421747401994584, not started
0 lock struct(s), heap size 1136, 0 row lock(s)
---TRANSACTION 421747401990328, not started
0 lock struct(s), heap size 1136, 0 row lock(s)
--------
FILE I/O
--------
I/O thread 0 state: waiting for completed aio requests (insert buffer thread)
I/O thread 1 state: waiting for completed aio requests (log thread)
I/O thread 2 state: waiting for completed aio requests (read thread)
I/O thread 3 state: waiting for completed aio requests (read thread)
I/O thread 4 state: waiting for completed aio requests (read thread)
I/O thread 5 state: waiting for completed aio requests (read thread)
I/O thread 6 state: waiting for completed aio requests (write thread)
I/O thread 7 state: waiting for completed aio requests (write thread)
I/O thread 8 state: waiting for completed aio requests (write thread)
I/O thread 9 state: waiting for completed aio requests (write thread)
Pending normal aio reads: [0, 0, 0, 0] , aio writes: [0, 0, 0, 0] ,
 ibuf aio reads:, log i/o's:, sync i/o's:
Pending flushes (fsync) log: 0; buffer pool: 0
286 OS file reads, 171 OS file writes, 22 OS fsyncs
0.00 reads/s, 0 avg bytes/read, 0.00 writes/s, 0.00 fsyncs/s
-------------------------------------
INSERT BUFFER AND ADAPTIVE HASH INDEX
-------------------------------------
Ibuf: size 1, free list len 0, seg size 2, 0 merges
merged operations:
 insert 0, delete mark 0, delete 0
discarded operations:
 insert 0, delete mark 0, delete 0
Hash table size 34679, node heap has 0 buffer(s)
Hash table size 34679, node heap has 0 buffer(s)
Hash table size 34679, node heap has 0 buffer(s)
Hash table size 34679, node heap has 0 buffer(s)
Hash table size 34679, node heap has 0 buffer(s)
Hash table size 34679, node heap has 0 buffer(s)
Hash table size 34679, node heap has 0 buffer(s)
Hash table size 34679, node heap has 0 buffer(s)
0.00 hash searches/s, 0.00 non-hash searches/s
---
LOG
---
Log sequence number 445926
Log flushed up to   445926
Pages flushed up to 445926
Last checkpoint at  445917
0 pending log flushes, 0 pending chkp writes
18 log i/o's done, 0.00 log i/o's/second
----------------------
BUFFER POOL AND MEMORY
----------------------
Total large memory allocated 167772160
Dictionary memory allocated 50768
Buffer pool size   8012
Free buffers       7611
Database pages     401
Old database pages 0
Modified db pages  0
Percent of dirty pages(LRU & free pages): 0.000
Max dirty pages percent: 75.000
Pending reads 0
Pending writes: LRU 0, flush list 0, single page 0
Pages made young 0, not young 0
0.00 youngs/s, 0.00 non-youngs/s
Pages read 264, created 137, written 156
0.00 reads/s, 0.00 creates/s, 0.00 writes/s
No buffer pool page gets since the last printout
Pages read ahead 0.00/s, evicted without access 0.00/s, Random read ahead 0.00/s
LRU len: 401, unzip_LRU len: 0
I/O sum[0]:cur[0], unzip sum[0]:cur[0]
--------------
ROW OPERATIONS
--------------
0 queries inside InnoDB, 0 queries in queue
0 read views open inside InnoDB
Process ID=4267, Main thread ID=140272021272320, state: sleeping
Number of rows inserted 1, updated 0, deleted 0, read 1
0.00 inserts/s, 0.00 updates/s, 0.00 deletes/s, 0.00 reads/s
Number of system rows inserted 0, updated 0, deleted 0, read 0
0.00 inserts/s, 0.00 updates/s, 0.00 deletes/s, 0.00 reads/s
----------------------------
END OF INNODB MONITOR OUTPUT
============================

1.1.1.2.8.24 SHOW ENGINES

Syntax

SHOW [STORAGE] ENGINES

Description

SHOW ENGINES displays status information about the server's storage engines. This is particularly useful for checking whether a storage engine is supported, or to see what the default engine is. SHOW TABLE TYPES is a deprecated synonym.

The information_schema.ENGINES table provides the same information.

Since storage engines are plugins, different information about them is also shown in the information_schema.PLUGINS table and by the SHOW PLUGINS statement.

Note that both MySQL's InnoDB and Percona's XtraDB replacement are labeled as InnoDB. However, if XtraDB is in use, it will be specified in the COMMENT field. See XtraDB and InnoDB. The same applies to FederatedX.

The output consists of the following columns:

  • Engine indicates the engine's name.
  • Support indicates whether the engine is installed, and whether it is the default engine for the current session.
  • Comment is a brief description.
  • Transactions, XA and Savepoints indicate whether transactions, XA transactions and transaction savepoints are supported by the engine.

Examples

SHOW ENGINES\G
*************************** 1. row ***************************
      Engine: InnoDB
     Support: DEFAULT
     Comment: Supports transactions, row-level locking, and foreign keys
Transactions: YES
          XA: YES
  Savepoints: YES
*************************** 2. row ***************************
      Engine: CSV
     Support: YES
     Comment: CSV storage engine
Transactions: NO
          XA: NO
  Savepoints: NO
*************************** 3. row ***************************
      Engine: MyISAM
     Support: YES
     Comment: MyISAM storage engine
Transactions: NO
          XA: NO
  Savepoints: NO
*************************** 4. row ***************************
      Engine: BLACKHOLE
     Support: YES
     Comment: /dev/null storage engine (anything you write to it disappears)
Transactions: NO
          XA: NO
  Savepoints: NO
*************************** 5. row ***************************
      Engine: FEDERATED
     Support: YES
     Comment: FederatedX pluggable storage engine
Transactions: YES
          XA: NO
  Savepoints: YES
*************************** 6. row ***************************
      Engine: MRG_MyISAM
     Support: YES
     Comment: Collection of identical MyISAM tables
Transactions: NO
          XA: NO
  Savepoints: NO
*************************** 7. row ***************************
      Engine: ARCHIVE
     Support: YES
     Comment: Archive storage engine
Transactions: NO
          XA: NO
  Savepoints: NO
*************************** 8. row ***************************
      Engine: MEMORY
     Support: YES
     Comment: Hash based, stored in memory, useful for temporary tables
Transactions: NO
          XA: NO
  Savepoints: NO
*************************** 9. row ***************************
      Engine: PERFORMANCE_SCHEMA
     Support: YES
     Comment: Performance Schema
Transactions: NO
          XA: NO
  Savepoints: NO
*************************** 10. row ***************************
      Engine: Aria
     Support: YES
     Comment: Crash-safe tables with MyISAM heritage
Transactions: NO
          XA: NO
  Savepoints: NO
10 rows in set (0.00 sec)

1.1.1.2.8.25 SHOW ERRORS

Syntax

SHOW ERRORS [LIMIT [offset,] row_count]
SHOW ERRORS [LIMIT row_count OFFSET offset]
SHOW COUNT(*) ERRORS

Contents

  1. Syntax
  2. Description
  3. Examples

Description

This statement is similar to SHOW WARNINGS, except that instead of displaying errors, warnings, and notes, it displays only errors.

The LIMIT clause has the same syntax as for the SELECT statement.

The SHOW COUNT(*) ERRORS statement displays the number of errors. You can also retrieve this number from the error_count variable.

SHOW COUNT(*) ERRORS;
SELECT @@error_count;

The value of error_count might be greater than the number of messages displayed by SHOW WARNINGS if the max_error_count system variable is set so low that not all messages are stored.

For a list of MariaDB error codes, see MariaDB Error Codes.

Examples

SELECT f();
ERROR 1305 (42000): FUNCTION f does not exist

SHOW COUNT(*) ERRORS;
+-----------------------+
| @@session.error_count |
+-----------------------+
|                     1 |
+-----------------------+

SHOW ERRORS;
+-------+------+---------------------------+
| Level | Code | Message                   |
+-------+------+---------------------------+
| Error | 1305 | FUNCTION f does not exist |
+-------+------+---------------------------+

1.1.1.2.8.26 SHOW EVENTS

Syntax

SHOW EVENTS [{FROM | IN} schema_name]
    [LIKE 'pattern' | WHERE expr]

Description

Shows information about Event Manager events (created with CREATE EVENT). Requires the EVENT privilege. Without any arguments, SHOW EVENTS lists all of the events in the current schema:

SELECT CURRENT_USER(), SCHEMA();
+----------------+----------+
| CURRENT_USER() | SCHEMA() |
+----------------+----------+
| jon@ghidora    | myschema |
+----------------+----------+

SHOW EVENTS\G
*************************** 1. row ***************************
                  Db: myschema
                Name: e_daily
             Definer: jon@ghidora
           Time zone: SYSTEM
                Type: RECURRING
          Execute at: NULL
      Interval value: 10
      Interval field: SECOND
              Starts: 2006-02-09 10:41:23
                Ends: NULL
              Status: ENABLED
          Originator: 0
character_set_client: latin1
collation_connection: latin1_swedish_ci
  Database Collation: latin1_swedish_ci

To see the event action, use SHOW CREATE EVENT instead, or look at the information_schema.EVENTS table.

To see events for a specific schema, use the FROM clause. For example, to see events for the test schema, use the following statement:

SHOW EVENTS FROM test;

The LIKE clause, if present, indicates which event names to match. The WHERE clause can be given to select rows using more general conditions, as discussed in Extended Show.

1.1.1.2.8.27 SHOW FUNCTION STATUS

Syntax

SHOW FUNCTION STATUS
    [LIKE 'pattern' | WHERE expr]

Description

This statement is similar to SHOW PROCEDURE STATUS but for stored functions.

The LIKE clause, if present on its own, indicates which function names to match.

The WHERE and LIKE clauses can be given to select rows using more general conditions, as discussed in Extended SHOW.

The information_schema.ROUTINES table contains more detailed information.

Examples

Showing all stored functions:

SHOW FUNCTION STATUS\G
*************************** 1. row ***************************
                  Db: test
                Name: VatCents
                Type: FUNCTION
             Definer: root@localhost
            Modified: 2013-06-01 12:40:31
             Created: 2013-06-01 12:40:31
       Security_type: DEFINER
             Comment: 
character_set_client: utf8
collation_connection: utf8_general_ci
  Database Collation: latin1_swedish_ci

Stored functions whose name starts with 'V': 

SHOW FUNCTION STATUS LIKE 'V%' \G
*************************** 1. row ***************************
                  Db: test
                Name: VatCents
                Type: FUNCTION
             Definer: root@localhost
            Modified: 2013-06-01 12:40:31
             Created: 2013-06-01 12:40:31
       Security_type: DEFINER
             Comment: 
character_set_client: utf8
collation_connection: utf8_general_ci
  Database Collation: latin1_swedish_ci

Stored functions with a security type of 'DEFINER':

SHOW FUNCTION STATUS WHERE Security_type LIKE 'DEFINER' \G
*************************** 1. row ***************************
                  Db: test
                Name: VatCents
                Type: FUNCTION
             Definer: root@localhost
            Modified: 2013-06-01 12:40:31
             Created: 2013-06-01 12:40:31
       Security_type: DEFINER
             Comment: 
character_set_client: utf8
collation_connection: utf8_general_ci
  Database Collation: latin1_swedish_ci

1.1.1.2.8.28 SHOW GRANTS

1.1.1.2.8.29 SHOW INDEX

1.1.1.2.8.30 SHOW INDEX_STATISTICS

Syntax

SHOW INDEX_STATISTICS

Description

The SHOW INDEX_STATISTICS statement was introduced in MariaDB 5.2 as part of the User Statistics feature. It was removed as a separate statement in MariaDB 10.1.1, but effectively replaced by the generic SHOW information_schema_table statement. The information_schmea.INDEX_STATISTICS table shows statistics on index usage and makes it possible to do such things as locating unused indexes and generating the commands to remove them.

The userstat system variable must be set to 1 to activate this feature. See the User Statistics and information_schema.INDEX_STATISTICS table for more information.

Example

SHOW INDEX_STATISTICS;
+--------------+-------------------+------------+-----------+
| Table_schema | Table_name        | Index_name | Rows_read |
+--------------+-------------------+------------+-----------+
| test         | employees_example | PRIMARY    |         1 |
+--------------+-------------------+------------+-----------+

1.1.1.2.8.32 SHOW LOCALES

SHOW LOCALES was introduced as part of the Information Schema plugin extension.

SHOW LOCALES is used to return locales information as part of the Locales plugin. While the information_schema.LOCALES table has 8 columns, the SHOW LOCALES statement will only display 4 of them:

Example

SHOW LOCALES;
+-----+-------+-------------------------------------+------------------------+
| Id  | Name  | Description                         | Error_Message_Language |
+-----+-------+-------------------------------------+------------------------+
|   0 | en_US | English - United States             | english                |
|   1 | en_GB | English - United Kingdom            | english                |
|   2 | ja_JP | Japanese - Japan                    | japanese               |
|   3 | sv_SE | Swedish - Sweden                    | swedish                |
...

1.1.1.2.8.33 SHOW BINLOG STATUS

1.1.1.2.8.34 SHOW OPEN TABLES

Syntax

SHOW OPEN TABLES [FROM db_name]
    [LIKE 'pattern' | WHERE expr]

Description

SHOW OPEN TABLES lists the non-TEMPORARY tables that are currently open in the table cache. See http://dev.mysql.com/doc/refman/5.1/en/table-cache.html.

The FROM and LIKE clauses may be used.

The FROM clause, if present, restricts the tables shown to those present in the db_name database.

The LIKE clause, if present on its own, indicates which table names to match. The WHERE and LIKE clauses can be given to select rows using more general conditions, as discussed in Extended SHOW.

The following information is returned:

ColumnDescription
DatabaseDatabase name.
NameTable name.
In_useNumber of table instances being used.
Name_locked1 if the table is name-locked, e.g. if it is being dropped or renamed, otherwise 0.

Before MariaDB 5.5, each use of, for example, LOCK TABLE ... WRITE would increment In_use for that table. With the implementation of the metadata locking improvements in MariaDB 5.5, LOCK TABLE... WRITE acquires a strong MDL lock, and concurrent connections will wait on this MDL lock, so any subsequent LOCK TABLE... WRITE will not increment In_use.

Example

SHOW OPEN TABLES;
+----------+---------------------------+--------+-------------+
| Database | Table                     | In_use | Name_locked |
+----------+---------------------------+--------+-------------+
...
| test     | xjson                     |      0 |           0 |
| test     | jauthor                   |      0 |           0 |
| test     | locks                     |      1 |           0 |
...
+----------+---------------------------+--------+-------------+

1.1.1.2.8.35 SHOW PACKAGE BODY STATUS

MariaDB starting with 10.3.5

Oracle-style packages were introduced in MariaDB 10.3.5.

Syntax

SHOW PACKAGE BODY STATUS
    [LIKE 'pattern' | WHERE expr]

Contents

  1. Syntax
  2. Description
  3. Examples
  4. See Also

Description

The SHOW PACKAGE BODY STATUS statement returns characteristics of stored package bodies (implementations), such as the database, name, type, creator, creation and modification dates, and character set information. A similar statement, SHOW PACKAGE STATUS, displays information about stored package specifications.

The LIKE clause, if present, indicates which package names to match. The WHERE and LIKE clauses can be given to select rows using more general conditions, as discussed in Extended SHOW.

The ROUTINES table in the INFORMATION_SCHEMA database contains more detailed information.

Examples

SHOW PACKAGE BODY STATUS LIKE 'pkg1'\G
*************************** 1. row ***************************
                  Db: test
                Name: pkg1
                Type: PACKAGE BODY
             Definer: root@localhost
            Modified: 2018-02-27 14:44:14
             Created: 2018-02-27 14:44:14
       Security_type: DEFINER
             Comment: This is my first package body
character_set_client: utf8
collation_connection: utf8_general_ci
  Database Collation: latin1_swedish_ci

See Also

1.1.1.2.8.36 SHOW PACKAGE STATUS

MariaDB starting with 10.3.5

Oracle-style packages were introduced in MariaDB 10.3.5.

Syntax

SHOW PACKAGE STATUS
    [LIKE 'pattern' | WHERE expr]

Contents

  1. Syntax
  2. Description
  3. Examples
  4. See Also

Description

The SHOW PACKAGE STATUS statement returns characteristics of stored package specifications, such as the database, name, type, creator, creation and modification dates, and character set information. A similar statement, SHOW PACKAGE BODY STATUS, displays information about stored package bodies (i.e. implementations).

The LIKE clause, if present, indicates which package names to match. The WHERE and LIKE clauses can be given to select rows using more general conditions, as discussed in Extended SHOW.

The ROUTINES table in the INFORMATION_SCHEMA database contains more detailed information.

Examples

SHOW PACKAGE STATUS LIKE 'pkg1'\G
*************************** 1. row ***************************
                  Db: test
                Name: pkg1
                Type: PACKAGE
             Definer: root@localhost
            Modified: 2018-02-27 14:38:15
             Created: 2018-02-27 14:38:15
       Security_type: DEFINER
             Comment: This is my first package
character_set_client: utf8
collation_connection: utf8_general_ci
  Database Collation: latin1_swedish_ci

See Also

1.1.1.2.8.37 SHOW PLUGINS

1.1.1.2.8.38 SHOW PLUGINS SONAME

1.1.1.2.8.39 SHOW PRIVILEGES

Syntax

SHOW PRIVILEGES

Description

SHOW PRIVILEGES shows the list of system privileges that the MariaDB server supports. The exact list of privileges depends on the version of your server.

Note that before MariaDB 10.3.23, MariaDB 10.4.13 and MariaDB 10.5.2 , the Delete history privilege displays as Delete versioning rows (MDEV-20382).

Example

From MariaDB 10.5.9

SHOW PRIVILEGES;
+--------------------------+---------------------------------------+--------------------------------------------------------------------+
| Privilege                | Context                               | Comment                                                            |
+--------------------------+---------------------------------------+--------------------------------------------------------------------+
| Alter                    | Tables                                | To alter the table                                                 |
| Alter routine            | Functions,Procedures                  | To alter or drop stored functions/procedures                       |
| Create                   | Databases,Tables,Indexes              | To create new databases and tables                                 |
| Create routine           | Databases                             | To use CREATE FUNCTION/PROCEDURE                                   |
| Create temporary tables  | Databases                             | To use CREATE TEMPORARY TABLE                                      |
| Create view              | Tables                                | To create new views                                                |
| Create user              | Server Admin                          | To create new users                                                |
| Delete                   | Tables                                | To delete existing rows                                            |
| Delete history           | Tables                                | To delete versioning table historical rows                         |
| Drop                     | Databases,Tables                      | To drop databases, tables, and views                               |
| Event                    | Server Admin                          | To create, alter, drop and execute events                          |
| Execute                  | Functions,Procedures                  | To execute stored routines                                         |
| File                     | File access on server                 | To read and write files on the server                              |
| Grant option             | Databases,Tables,Functions,Procedures | To give to other users those privileges you possess                |
| Index                    | Tables                                | To create or drop indexes                                          |
| Insert                   | Tables                                | To insert data into tables                                         |
| Lock tables              | Databases                             | To use LOCK TABLES (together with SELECT privilege)                |
| Process                  | Server Admin                          | To view the plain text of currently executing queries              |
| Proxy                    | Server Admin                          | To make proxy user possible                                        |
| References               | Databases,Tables                      | To have references on tables                                       |
| Reload                   | Server Admin                          | To reload or refresh tables, logs and privileges                   |
| Binlog admin             | Server                                | To purge binary logs                                               |
| Binlog monitor           | Server                                | To use SHOW BINLOG STATUS and SHOW BINARY LOG                      |
| Binlog replay            | Server                                | To use BINLOG (generated by mariadb-binlog)                        |
| Replication master admin | Server                                | To monitor connected slaves                                        |
| Replication slave admin  | Server                                | To start/stop slave and apply binlog events                        |
| Slave monitor            | Server                                | To use SHOW SLAVE STATUS and SHOW RELAYLOG EVENTS                  |
| Replication slave        | Server Admin                          | To read binary log events from the master                          |
| Select                   | Tables                                | To retrieve rows from table                                        |
| Show databases           | Server Admin                          | To see all databases with SHOW DATABASES                           |
| Show view                | Tables                                | To see views with SHOW CREATE VIEW                                 |
| Shutdown                 | Server Admin                          | To shut down the server                                            |
| Super                    | Server Admin                          | To use KILL thread, SET GLOBAL, CHANGE MASTER, etc.                |
| Trigger                  | Tables                                | To use triggers                                                    |
| Create tablespace        | Server Admin                          | To create/alter/drop tablespaces                                   |
| Update                   | Tables                                | To update existing rows                                            |
| Set user                 | Server                                | To create views and stored routines with a different definer       |
| Federated admin          | Server                                | To execute the CREATE SERVER, ALTER SERVER, DROP SERVER statements |
| Connection admin         | Server                                | To bypass connection limits and kill other users' connections      |
| Read_only admin          | Server                                | To perform write operations even if @@read_only=ON                 |
| Usage                    | Server Admin                          | No privileges - allow connect only                                 |
+--------------------------+---------------------------------------+--------------------------------------------------------------------+
41 rows in set (0.000 sec)

See Also

1.1.1.2.8.40 SHOW PROCEDURE CODE

Syntax

SHOW PROCEDURE CODE proc_name

Contents

  1. Syntax
  2. Description
  3. Examples
  4. See Also

Description

This statement is a MariaDB extension that is available only for servers that have been built with debugging support. It displays a representation of the internal implementation of the named stored procedure. A similar statement, SHOW FUNCTION CODE, displays information about stored functions.

Both statements require that you be the owner of the routine or have SELECT access to the mysql.proc table.

If the named routine is available, each statement produces a result set. Each row in the result set corresponds to one "instruction" in the routine. The first column is Pos, which is an ordinal number beginning with 0. The second column is Instruction, which contains an SQL statement (usually changed from the original source), or a directive which has meaning only to the stored-routine handler.

Examples

DELIMITER //

CREATE PROCEDURE p1 ()
  BEGIN
    DECLARE fanta INT DEFAULT 55;
    DROP TABLE t2;
    LOOP
      INSERT INTO t3 VALUES (fanta);
      END LOOP;
  END//
Query OK, 0 rows affected (0.00 sec)

SHOW PROCEDURE CODE p1//
+-----+----------------------------------------+
| Pos | Instruction                            |
+-----+----------------------------------------+
|   0 | set fanta@0 55                         |
|   1 | stmt 9 "DROP TABLE t2"                 |
|   2 | stmt 5 "INSERT INTO t3 VALUES (fanta)" |
|   3 | jump 2                                 |
+-----+----------------------------------------+

See Also

1.1.1.2.8.41 SHOW PROCEDURE STATUS

Syntax

SHOW PROCEDURE STATUS
    [LIKE 'pattern' | WHERE expr]

Description

This statement is a MariaDB extension. It returns characteristics of a stored procedure, such as the database, name, type, creator, creation and modification dates, and character set information. A similar statement, SHOW FUNCTION STATUS, displays information about stored functions.

The LIKE clause, if present, indicates which procedure or function names to match. The WHERE and LIKE clauses can be given to select rows using more general conditions, as discussed in Extended SHOW.

The ROUTINES table in the INFORMATION_SCHEMA database contains more detailed information.

Examples

SHOW PROCEDURE STATUS LIKE 'p1'\G
*************************** 1. row ***************************
                  Db: test
                Name: p1
                Type: PROCEDURE
             Definer: root@localhost
            Modified: 2010-08-23 13:23:03
             Created: 2010-08-23 13:23:03
       Security_type: DEFINER
             Comment: 
character_set_client: latin1
collation_connection: latin1_swedish_ci
  Database Collation: latin1_swedish_ci

See Also

1.1.1.2.8.42 SHOW PROCESSLIST

Syntax

SHOW [FULL] PROCESSLIST

Description

SHOW PROCESSLIST shows you which threads are running. You can also get this information from the information_schema.PROCESSLIST table or the mysqladmin processlist command. If you have the PROCESS privilege, you can see all threads. Otherwise, you can see only your own threads (that is, threads associated with the MariaDB account that you are using). If you do not use the FULL keyword, only the first 100 characters of each statement are shown in the Info field.

The columns shown in SHOW PROCESSLIST are:

NameDescription
IDThe client's process ID.
USERThe username associated with the process.
HOSTThe host the client is connected to.
DBThe default database of the process (NULL if no default).
COMMANDThe command type. See Thread Command Values.
TIMEThe amount of time, in seconds, the process has been in its current state. For a replica SQL thread before MariaDB 10.1, this is the time in seconds between the last replicated event's timestamp and the replica machine's real time.
STATESee Thread States.
INFOThe statement being executed.
PROGRESSThe total progress of the process (0-100%) (see Progress Reporting).

See TIME_MS column in information_schema.PROCESSLIST for differences in the TIME column between MariaDB and MySQL.

The information_schema.PROCESSLIST table contains the following additional columns:

NameDescription
TIME_MSThe amount of time, in milliseconds, the process has been in its current state.
STAGEThe stage the process is currently in.
MAX_STAGEThe maximum number of stages.
PROGRESSThe progress of the process within the current stage (0-100%).
MEMORY_USEDThe amount of memory used by the process.
EXAMINED_ROWSThe number of rows the process has examined.
QUERY_IDQuery ID.

Note that the PROGRESS field from the information schema, and the PROGRESS field from SHOW PROCESSLIST display different results. SHOW PROCESSLIST shows the total progress, while the information schema shows the progress for the current stage only.

Threads can be killed using their thread_id or their query_id, with the KILL statement.

Since queries on this table are locking, if the performance_schema is enabled, you may want to query the THREADS table instead.

Examples

SHOW PROCESSLIST;
+----+-----------------+-----------+------+---------+------+------------------------+------------------+----------+
| Id | User            | Host      | db   | Command | Time | State                  | Info             | Progress |
+----+-----------------+-----------+------+---------+------+------------------------+------------------+----------+
|  2 | event_scheduler | localhost | NULL | Daemon  | 2693 | Waiting on empty queue | NULL             |    0.000 |
|  4 | root            | localhost | NULL | Query   |    0 | Table lock             | SHOW PROCESSLIST |    0.000 |
+----+-----------------+-----------+------+---------+------+------------------------+------------------+----------+

See also

CONNECTION_ID()

1.1.1.2.8.43 SHOW PROFILES

Syntax

SHOW PROFILES

Description

The SHOW PROFILES statement displays profiling information that indicates resource usage for statements executed during the course of the current session. It is used together with SHOW PROFILE.

1.1.1.2.8.44 SHOW QUERY_RESPONSE_TIME

It is possible to use SHOW QUERY_RESPONSE_TIME as an alternative for retrieving information from the QUERY_RESPONSE_TIME plugin.

This was introduced as part of the Information Schema plugin extension.

1.1.1.2.8.45 SHOW RELAYLOG EVENTS

1.1.1.2.8.46 SHOW REPLICA HOSTS

1.1.1.2.8.47 SHOW REPLICA STATUS

1.1.1.2.8.48 SHOW STATUS

Syntax

SHOW [GLOBAL | SESSION] STATUS
    [LIKE 'pattern' | WHERE expr]

Description

SHOW STATUS provides server status information. This information also can be obtained using the mysqladmin extended-status command, or by querying the Information Schema GLOBAL_STATUS and SESSION_STATUS tables. The LIKE clause, if present, indicates which variable names to match. The WHERE clause can be given to select rows using more general conditions.

With the GLOBAL modifier, SHOW STATUS displays the status values for all connections to MariaDB. With SESSION, it displays the status values for the current connection. If no modifier is present, the default is SESSION. LOCAL is a synonym for SESSION. If you see a lot of 0 values, the reason is probably that you have used SHOW STATUS with a new connection instead of SHOW GLOBAL STATUS.

Some status variables have only a global value. For these, you get the same value for both GLOBAL and SESSION.

See Server Status Variables for a full list, scope and description of the variables that can be viewed with SHOW STATUS.

The LIKE clause, if present on its own, indicates which variable name to match.

The WHERE and LIKE clauses can be given to select rows using more general conditions, as discussed in Extended SHOW.

Examples

Full output from MariaDB 10.1.17:

SHOW GLOBAL STATUS;
+--------------------------------------------------------------+----------------------------------------+
| Variable_name                                                | Value                                  |
+--------------------------------------------------------------+----------------------------------------+
| Aborted_clients                                              | 0                                      |
| Aborted_connects                                             | 0                                      |
| Access_denied_errors                                         | 0                                      |
| Acl_column_grants                                            | 0                                      |
| Acl_database_grants                                          | 2                                      |
| Acl_function_grants                                          | 0                                      |
| Acl_procedure_grants                                         | 0                                      |
| Acl_proxy_users                                              | 2                                      |
| Acl_role_grants                                              | 0                                      |
| Acl_roles                                                    | 0                                      |
| Acl_table_grants                                             | 0                                      |
| Acl_users                                                    | 6                                      |
| Aria_pagecache_blocks_not_flushed                            | 0                                      |
| Aria_pagecache_blocks_unused                                 | 15706                                  |
| Aria_pagecache_blocks_used                                   | 0                                      |
| Aria_pagecache_read_requests                                 | 0                                      |
| Aria_pagecache_reads                                         | 0                                      |
| Aria_pagecache_write_requests                                | 0                                      |
| Aria_pagecache_writes                                        | 0                                      |
| Aria_transaction_log_syncs                                   | 0                                      |
| Binlog_commits                                               | 0                                      |
| Binlog_group_commits                                         | 0                                      |
| Binlog_group_commit_trigger_count                            | 0                                      |
| Binlog_group_commit_trigger_lock_wait                        | 0                                      |
| Binlog_group_commit_trigger_timeout                          | 0                                      |
| Binlog_snapshot_file                                         |                                        |
| Binlog_snapshot_position                                     | 0                                      |
| Binlog_bytes_written                                         | 0                                      |
| Binlog_cache_disk_use                                        | 0                                      |
| Binlog_cache_use                                             | 0                                      |
| Binlog_stmt_cache_disk_use                                   | 0                                      |
| Binlog_stmt_cache_use                                        | 0                                      |
| Busy_time                                                    | 0.000000                               |
| Bytes_received                                               | 432                                    |
| Bytes_sent                                                   | 15183                                  |
| Com_admin_commands                                           | 1                                      |
| Com_alter_db                                                 | 0                                      |
| Com_alter_db_upgrade                                         | 0                                      |
| Com_alter_event                                              | 0                                      |
| Com_alter_function                                           | 0                                      |
| Com_alter_procedure                                          | 0                                      |
| Com_alter_server                                             | 0                                      |
| Com_alter_table                                              | 0                                      |
| Com_alter_tablespace                                         | 0                                      |
| Com_analyze                                                  | 0                                      |
| Com_assign_to_keycache                                       | 0                                      |
| Com_begin                                                    | 0                                      |
| Com_binlog                                                   | 0                                      |
| Com_call_procedure                                           | 0                                      |
| Com_change_db                                                | 0                                      |
| Com_change_master                                            | 0                                      |
| Com_check                                                    | 0                                      |
| Com_checksum                                                 | 0                                      |
| Com_commit                                                   | 0                                      |
| Com_compound_sql                                             | 0                                      |
| Com_create_db                                                | 0                                      |
| Com_create_event                                             | 0                                      |
| Com_create_function                                          | 0                                      |
| Com_create_index                                             | 0                                      |
| Com_create_procedure                                         | 0                                      |
| Com_create_role                                              | 0                                      |
| Com_create_server                                            | 0                                      |
| Com_create_table                                             | 0                                      |
| Com_create_temporary_table                                   | 0                                      |
| Com_create_trigger                                           | 0                                      |
| Com_create_udf                                               | 0                                      |
| Com_create_user                                              | 0                                      |
| Com_create_view                                              | 0                                      |
| Com_dealloc_sql                                              | 0                                      |
| Com_delete                                                   | 0                                      |
| Com_delete_multi                                             | 0                                      |
| Com_do                                                       | 0                                      |
| Com_drop_db                                                  | 0                                      |
| Com_drop_event                                               | 0                                      |
| Com_drop_function                                            | 0                                      |
| Com_drop_index                                               | 0                                      |
| Com_drop_procedure                                           | 0                                      |
| Com_drop_role                                                | 0                                      |
| Com_drop_server                                              | 0                                      |
| Com_drop_table                                               | 0                                      |
| Com_drop_temporary_table                                     | 0                                      |
| Com_drop_trigger                                             | 0                                      |
| Com_drop_user                                                | 0                                      |
| Com_drop_view                                                | 0                                      |
| Com_empty_query                                              | 0                                      |
| Com_execute_sql                                              | 0                                      |
| Com_flush                                                    | 0                                      |
| Com_get_diagnostics                                          | 0                                      |
| Com_grant                                                    | 0                                      |
| Com_grant_role                                               | 0                                      |
| Com_ha_close                                                 | 0                                      |
| Com_ha_open                                                  | 0                                      |
| Com_ha_read                                                  | 0                                      |
| Com_help                                                     | 0                                      |
| Com_insert                                                   | 0                                      |
| Com_insert_select                                            | 0                                      |
| Com_install_plugin                                           | 0                                      |
| Com_kill                                                     | 0                                      |
| Com_load                                                     | 0                                      |
| Com_lock_tables                                              | 0                                      |
| Com_optimize                                                 | 0                                      |
| Com_preload_keys                                             | 0                                      |
| Com_prepare_sql                                              | 0                                      |
| Com_purge                                                    | 0                                      |
| Com_purge_before_date                                        | 0                                      |
| Com_release_savepoint                                        | 0                                      |
| Com_rename_table                                             | 0                                      |
| Com_rename_user                                              | 0                                      |
| Com_repair                                                   | 0                                      |
| Com_replace                                                  | 0                                      |
| Com_replace_select                                           | 0                                      |
| Com_reset                                                    | 0                                      |
| Com_resignal                                                 | 0                                      |
| Com_revoke                                                   | 0                                      |
| Com_revoke_all                                               | 0                                      |
| Com_revoke_role                                              | 0                                      |
| Com_rollback                                                 | 0                                      |
| Com_rollback_to_savepoint                                    | 0                                      |
| Com_savepoint                                                | 0                                      |
| Com_select                                                   | 1                                      |
| Com_set_option                                               | 0                                      |
| Com_show_authors                                             | 0                                      |
| Com_show_binlog_events                                       | 0                                      |
| Com_show_binlogs                                             | 0                                      |
| Com_show_charsets                                            | 0                                      |
| Com_show_collations                                          | 0                                      |
| Com_show_contributors                                        | 0                                      |
| Com_show_create_db                                           | 0                                      |
| Com_show_create_event                                        | 0                                      |
| Com_show_create_func                                         | 0                                      |
| Com_show_create_proc                                         | 0                                      |
| Com_show_create_table                                        | 0                                      |
| Com_show_create_trigger                                      | 0                                      |
| Com_show_databases                                           | 0                                      |
| Com_show_engine_logs                                         | 0                                      |
| Com_show_engine_mutex                                        | 0                                      |
| Com_show_engine_status                                       | 0                                      |
| Com_show_errors                                              | 0                                      |
| Com_show_events                                              | 0                                      |
| Com_show_explain                                             | 0                                      |
| Com_show_fields                                              | 0                                      |
| Com_show_function_status                                     | 0                                      |
| Com_show_generic                                             | 0                                      |
| Com_show_grants                                              | 0                                      |
| Com_show_keys                                                | 0                                      |
| Com_show_master_status                                       | 0                                      |
| Com_show_open_tables                                         | 0                                      |
| Com_show_plugins                                             | 0                                      |
| Com_show_privileges                                          | 0                                      |
| Com_show_procedure_status                                    | 0                                      |
| Com_show_processlist                                         | 0                                      |
| Com_show_profile                                             | 0                                      |
| Com_show_profiles                                            | 0                                      |
| Com_show_relaylog_events                                     | 0                                      |
| Com_show_slave_hosts                                         | 0                                      |
| Com_show_slave_status                                        | 0                                      |
| Com_show_status                                              | 2                                      |
| Com_show_storage_engines                                     | 0                                      |
| Com_show_table_status                                        | 0                                      |
| Com_show_tables                                              | 0                                      |
| Com_show_triggers                                            | 0                                      |
| Com_show_variables                                           | 0                                      |
| Com_show_warnings                                            | 0                                      |
| Com_shutdown                                                 | 0                                      |
| Com_signal                                                   | 0                                      |
| Com_start_all_slaves                                         | 0                                      |
| Com_start_slave                                              | 0                                      |
| Com_stmt_close                                               | 0                                      |
| Com_stmt_execute                                             | 0                                      |
| Com_stmt_fetch                                               | 0                                      |
| Com_stmt_prepare                                             | 0                                      |
| Com_stmt_reprepare                                           | 0                                      |
| Com_stmt_reset                                               | 0                                      |
| Com_stmt_send_long_data                                      | 0                                      |
| Com_stop_all_slaves                                          | 0                                      |
| Com_stop_slave                                               | 0                                      |
| Com_truncate                                                 | 0                                      |
| Com_uninstall_plugin                                         | 0                                      |
| Com_unlock_tables                                            | 0                                      |
| Com_update                                                   | 0                                      |
| Com_update_multi                                             | 0                                      |
| Com_xa_commit                                                | 0                                      |
| Com_xa_end                                                   | 0                                      |
| Com_xa_prepare                                               | 0                                      |
| Com_xa_recover                                               | 0                                      |
| Com_xa_rollback                                              | 0                                      |
| Com_xa_start                                                 | 0                                      |
| Compression                                                  | OFF                                    |
| Connection_errors_accept                                     | 0                                      |
| Connection_errors_internal                                   | 0                                      |
| Connection_errors_max_connections                            | 0                                      |
| Connection_errors_peer_address                               | 0                                      |
| Connection_errors_select                                     | 0                                      |
| Connection_errors_tcpwrap                                    | 0                                      |
| Connections                                                  | 4                                      |
| Cpu_time                                                     | 0.000000                               |
| Created_tmp_disk_tables                                      | 0                                      |
| Created_tmp_files                                            | 6                                      |
| Created_tmp_tables                                           | 2                                      |
| Delayed_errors                                               | 0                                      |
| Delayed_insert_threads                                       | 0                                      |
| Delayed_writes                                               | 0                                      |
| Delete_scan                                                  | 0                                      |
| Empty_queries                                                | 0                                      |
| Executed_events                                              | 0                                      |
| Executed_triggers                                            | 0                                      |
| Feature_delay_key_write                                      | 0                                      |
| Feature_dynamic_columns                                      | 0                                      |
| Feature_fulltext                                             | 0                                      |
| Feature_gis                                                  | 0                                      |
| Feature_locale                                               | 0                                      |
| Feature_subquery                                             | 0                                      |
| Feature_timezone                                             | 0                                      |
| Feature_trigger                                              | 0                                      |
| Feature_xml                                                  | 0                                      |
| Flush_commands                                               | 1                                      |
| Handler_commit                                               | 1                                      |
| Handler_delete                                               | 0                                      |
| Handler_discover                                             | 0                                      |
| Handler_external_lock                                        | 0                                      |
| Handler_icp_attempts                                         | 0                                      |
| Handler_icp_match                                            | 0                                      |
| Handler_mrr_init                                             | 0                                      |
| Handler_mrr_key_refills                                      | 0                                      |
| Handler_mrr_rowid_refills                                    | 0                                      |
| Handler_prepare                                              | 0                                      |
| Handler_read_first                                           | 3                                      |
| Handler_read_key                                             | 0                                      |
| Handler_read_last                                            | 0                                      |
| Handler_read_next                                            | 0                                      |
| Handler_read_prev                                            | 0                                      |
| Handler_read_retry                                           | 0                                      |
| Handler_read_rnd                                             | 0                                      |
| Handler_read_rnd_deleted                                     | 0                                      |
| Handler_read_rnd_next                                        | 537                                    |
| Handler_rollback                                             | 0                                      |
| Handler_savepoint                                            | 0                                      |
| Handler_savepoint_rollback                                   | 0                                      |
| Handler_tmp_update                                           | 0                                      |
| Handler_tmp_write                                            | 516                                    |
| Handler_update                                               | 0                                      |
| Handler_write                                                | 0                                      |
| Innodb_available_undo_logs                                   | 128                                    |
| Innodb_background_log_sync                                   | 222                                    |
| Innodb_buffer_pool_bytes_data                                | 2523136                                |
| Innodb_buffer_pool_bytes_dirty                               | 0                                      |
| Innodb_buffer_pool_dump_status                               | Dumping buffer pool(s) not yet started |
| Innodb_buffer_pool_load_status                               | Loading buffer pool(s) not yet started |
| Innodb_buffer_pool_pages_data                                | 154                                    |
| Innodb_buffer_pool_pages_dirty                               | 0                                      |
| Innodb_buffer_pool_pages_flushed                             | 1                                      |
| Innodb_buffer_pool_pages_free                                | 8037                                   |
| Innodb_buffer_pool_pages_lru_flushed                         | 0                                      |
| Innodb_buffer_pool_pages_made_not_young                      | 0                                      |
| Innodb_buffer_pool_pages_made_young                          | 0                                      |
| Innodb_buffer_pool_pages_misc                                | 0                                      |
| Innodb_buffer_pool_pages_old                                 | 0                                      |
| Innodb_buffer_pool_pages_total                               | 8191                                   |
| Innodb_buffer_pool_read_ahead                                | 0                                      |
| Innodb_buffer_pool_read_ahead_evicted                        | 0                                      |
| Innodb_buffer_pool_read_ahead_rnd                            | 0                                      |
| Innodb_buffer_pool_read_requests                             | 558                                    |
| Innodb_buffer_pool_reads                                     | 155                                    |
| Innodb_buffer_pool_wait_free                                 | 0                                      |
| Innodb_buffer_pool_write_requests                            | 1                                      |
| Innodb_checkpoint_age                                        | 0                                      |
| Innodb_checkpoint_max_age                                    | 80826164                               |
| Innodb_data_fsyncs                                           | 5                                      |
| Innodb_data_pending_fsyncs                                   | 0                                      |
| Innodb_data_pending_reads                                    | 0                                      |
| Innodb_data_pending_writes                                   | 0                                      |
| Innodb_data_read                                             | 2609664                                |
| Innodb_data_reads                                            | 172                                    |
| Innodb_data_writes                                           | 5                                      |
| Innodb_data_written                                          | 34304                                  |
| Innodb_dblwr_pages_written                                   | 1                                      |
| Innodb_dblwr_writes                                          | 1                                      |
| Innodb_deadlocks                                             | 0                                      |
| Innodb_have_atomic_builtins                                  | ON                                     |
| Innodb_history_list_length                                   | 0                                      |
| Innodb_ibuf_discarded_delete_marks                           | 0                                      |
| Innodb_ibuf_discarded_deletes                                | 0                                      |
| Innodb_ibuf_discarded_inserts                                | 0                                      |
| Innodb_ibuf_free_list                                        | 0                                      |
| Innodb_ibuf_merged_delete_marks                              | 0                                      |
| Innodb_ibuf_merged_deletes                                   | 0                                      |
| Innodb_ibuf_merged_inserts                                   | 0                                      |
| Innodb_ibuf_merges                                           | 0                                      |
| Innodb_ibuf_segment_size                                     | 2                                      |
| Innodb_ibuf_size                                             | 1                                      |
| Innodb_log_waits                                             | 0                                      |
| Innodb_log_write_requests                                    | 0                                      |
| Innodb_log_writes                                            | 1                                      |
| Innodb_lsn_current                                           | 1616829                                |
| Innodb_lsn_flushed                                           | 1616829                                |
| Innodb_lsn_last_checkpoint                                   | 1616829                                |
| Innodb_master_thread_active_loops                            | 0                                      |
| Innodb_master_thread_idle_loops                              | 222                                    |
| Innodb_max_trx_id                                            | 2308                                   |
| Innodb_mem_adaptive_hash                                     | 2217568                                |
| Innodb_mem_dictionary                                        | 630703                                 |
| Innodb_mem_total                                             | 140771328                              |
| Innodb_mutex_os_waits                                        | 1                                      |
| Innodb_mutex_spin_rounds                                     | 30                                     |
| Innodb_mutex_spin_waits                                      | 1                                      |
| Innodb_oldest_view_low_limit_trx_id                          | 0                                      |
| Innodb_os_log_fsyncs                                         | 3                                      |
| Innodb_os_log_pending_fsyncs                                 | 0                                      |
| Innodb_os_log_pending_writes                                 | 0                                      |
| Innodb_os_log_written                                        | 512                                    |
| Innodb_page_size                                             | 16384                                  |
| Innodb_pages_created                                         | 0                                      |
| Innodb_pages_read                                            | 154                                    |
| Innodb_pages_written                                         | 1                                      |
| Innodb_purge_trx_id                                          | 0                                      |
| Innodb_purge_undo_no                                         | 0                                      |
| Innodb_read_views_memory                                     | 88                                     |
| Innodb_row_lock_current_waits                                | 0                                      |
| Innodb_row_lock_time                                         | 0                                      |
| Innodb_row_lock_time_avg                                     | 0                                      |
| Innodb_row_lock_time_max                                     | 0                                      |
| Innodb_row_lock_waits                                        | 0                                      |
| Innodb_rows_deleted                                          | 0                                      |
| Innodb_rows_inserted                                         | 0                                      |
| Innodb_rows_read                                             | 0                                      |
| Innodb_rows_updated                                          | 0                                      |
| Innodb_system_rows_deleted                                   | 0                                      |
| Innodb_system_rows_inserted                                  | 0                                      |
| Innodb_system_rows_read                                      | 0                                      |
| Innodb_system_rows_updated                                   | 0                                      |
| Innodb_s_lock_os_waits                                       | 2                                      |
| Innodb_s_lock_spin_rounds                                    | 60                                     |
| Innodb_s_lock_spin_waits                                     | 2                                      |
| Innodb_truncated_status_writes                               | 0                                      |
| Innodb_x_lock_os_waits                                       | 0                                      |
| Innodb_x_lock_spin_rounds                                    | 0                                      |
| Innodb_x_lock_spin_waits                                     | 0                                      |
| Innodb_page_compression_saved                                | 0                                      |
| Innodb_page_compression_trim_sect512                         | 0                                      |
| Innodb_page_compression_trim_sect1024                        | 0                                      |
| Innodb_page_compression_trim_sect2048                        | 0                                      |
| Innodb_page_compression_trim_sect4096                        | 0                                      |
| Innodb_page_compression_trim_sect8192                        | 0                                      |
| Innodb_page_compression_trim_sect16384                       | 0                                      |
| Innodb_page_compression_trim_sect32768                       | 0                                      |
| Innodb_num_index_pages_written                               | 0                                      |
| Innodb_num_non_index_pages_written                           | 5                                      |
| Innodb_num_pages_page_compressed                             | 0                                      |
| Innodb_num_page_compressed_trim_op                           | 0                                      |
| Innodb_num_page_compressed_trim_op_saved                     | 0                                      |
| Innodb_num_pages_page_decompressed                           | 0                                      |
| Innodb_num_pages_page_compression_error                      | 0                                      |
| Innodb_num_pages_encrypted                                   | 0                                      |
| Innodb_num_pages_decrypted                                   | 0                                      |
| Innodb_have_lz4                                              | OFF                                    |
| Innodb_have_lzo                                              | OFF                                    |
| Innodb_have_lzma                                             | OFF                                    |
| Innodb_have_bzip2                                            | OFF                                    |
| Innodb_have_snappy                                           | OFF                                    |
| Innodb_defragment_compression_failures                       | 0                                      |
| Innodb_defragment_failures                                   | 0                                      |
| Innodb_defragment_count                                      | 0                                      |
| Innodb_onlineddl_rowlog_rows                                 | 0                                      |
| Innodb_onlineddl_rowlog_pct_used                             | 0                                      |
| Innodb_onlineddl_pct_progress                                | 0                                      |
| Innodb_secondary_index_triggered_cluster_reads               | 0                                      |
| Innodb_secondary_index_triggered_cluster_reads_avoided       | 0                                      |
| Innodb_encryption_rotation_pages_read_from_cache             | 0                                      |
| Innodb_encryption_rotation_pages_read_from_disk              | 0                                      |
| Innodb_encryption_rotation_pages_modified                    | 0                                      |
| Innodb_encryption_rotation_pages_flushed                     | 0                                      |
| Innodb_encryption_rotation_estimated_iops                    | 0                                      |
| Innodb_scrub_background_page_reorganizations                 | 0                                      |
| Innodb_scrub_background_page_splits                          | 0                                      |
| Innodb_scrub_background_page_split_failures_underflow        | 0                                      |
| Innodb_scrub_background_page_split_failures_out_of_filespace | 0                                      |
| Innodb_scrub_background_page_split_failures_missing_index    | 0                                      |
| Innodb_scrub_background_page_split_failures_unknown          | 0                                      |
| Key_blocks_not_flushed                                       | 0                                      |
| Key_blocks_unused                                            | 107163                                 |
| Key_blocks_used                                              | 0                                      |
| Key_blocks_warm                                              | 0                                      |
| Key_read_requests                                            | 0                                      |
| Key_reads                                                    | 0                                      |
| Key_write_requests                                           | 0                                      |
| Key_writes                                                   | 0                                      |
| Last_query_cost                                              | 0.000000                               |
| Master_gtid_wait_count                                       | 0                                      |
| Master_gtid_wait_time                                        | 0                                      |
| Master_gtid_wait_timeouts                                    | 0                                      |
| Max_statement_time_exceeded                                  | 0                                      |
| Max_used_connections                                         | 1                                      |
| Memory_used                                                  | 273614696                              |
| Not_flushed_delayed_rows                                     | 0                                      |
| Open_files                                                   | 25                                     |
| Open_streams                                                 | 0                                      |
| Open_table_definitions                                       | 18                                     |
| Open_tables                                                  | 11                                     |
| Opened_files                                                 | 77                                     |
| Opened_plugin_libraries                                      | 0                                      |
| Opened_table_definitions                                     | 18                                     |
| Opened_tables                                                | 18                                     |
| Opened_views                                                 | 0                                      |
| Performance_schema_accounts_lost                             | 0                                      |
| Performance_schema_cond_classes_lost                         | 0                                      |
| Performance_schema_cond_instances_lost                       | 0                                      |
| Performance_schema_digest_lost                               | 0                                      |
| Performance_schema_file_classes_lost                         | 0                                      |
| Performance_schema_file_handles_lost                         | 0                                      |
| Performance_schema_file_instances_lost                       | 0                                      |
| Performance_schema_hosts_lost                                | 0                                      |
| Performance_schema_locker_lost                               | 0                                      |
| Performance_schema_mutex_classes_lost                        | 0                                      |
| Performance_schema_mutex_instances_lost                      | 0                                      |
| Performance_schema_rwlock_classes_lost                       | 0                                      |
| Performance_schema_rwlock_instances_lost                     | 0                                      |
| Performance_schema_session_connect_attrs_lost                | 0                                      |
| Performance_schema_socket_classes_lost                       | 0                                      |
| Performance_schema_socket_instances_lost                     | 0                                      |
| Performance_schema_stage_classes_lost                        | 0                                      |
| Performance_schema_statement_classes_lost                    | 0                                      |
| Performance_schema_table_handles_lost                        | 0                                      |
| Performance_schema_table_instances_lost                      | 0                                      |
| Performance_schema_thread_classes_lost                       | 0                                      |
| Performance_schema_thread_instances_lost                     | 0                                      |
| Performance_schema_users_lost                                | 0                                      |
| Prepared_stmt_count                                          | 0                                      |
| Qcache_free_blocks                                           | 1                                      |
| Qcache_free_memory                                           | 1031336                                |
| Qcache_hits                                                  | 0                                      |
| Qcache_inserts                                               | 0                                      |
| Qcache_lowmem_prunes                                         | 0                                      |
| Qcache_not_cached                                            | 0                                      |
| Qcache_queries_in_cache                                      | 0                                      |
| Qcache_total_blocks                                          | 1                                      |
| Queries                                                      | 4                                      |
| Questions                                                    | 4                                      |
| Rows_read                                                    | 10                                     |
| Rows_sent                                                    | 517                                    |
| Rows_tmp_read                                                | 516                                    |
| Rpl_status                                                   | AUTH_MASTER                            |
| Select_full_join                                             | 0                                      |
| Select_full_range_join                                       | 0                                      |
| Select_range                                                 | 0                                      |
| Select_range_check                                           | 0                                      |
| Select_scan                                                  | 2                                      |
| Slave_connections                                            | 0                                      |
| Slave_heartbeat_period                                       | 0.000                                  |
| Slave_open_temp_tables                                       | 0                                      |
| Slave_received_heartbeats                                    | 0                                      |
| Slave_retried_transactions                                   | 0                                      |
| Slave_running                                                | OFF                                    |
| Slave_skipped_errors                                         | 0                                      |
| Slaves_connected                                             | 0                                      |
| Slaves_running                                               | 0                                      |
| Slow_launch_threads                                          | 0                                      |
| Slow_queries                                                 | 0                                      |
| Sort_merge_passes                                            | 0                                      |
| Sort_priority_queue_sorts                                    | 0                                      |
| Sort_range                                                   | 0                                      |
| Sort_rows                                                    | 0                                      |
| Sort_scan                                                    | 0                                      |
| Ssl_accept_renegotiates                                      | 0                                      |
| Ssl_accepts                                                  | 0                                      |
| Ssl_callback_cache_hits                                      | 0                                      |
| Ssl_cipher                                                   |                                        |
| Ssl_cipher_list                                              |                                        |
| Ssl_client_connects                                          | 0                                      |
| Ssl_connect_renegotiates                                     | 0                                      |
| Ssl_ctx_verify_depth                                         | 0                                      |
| Ssl_ctx_verify_mode                                          | 0                                      |
| Ssl_default_timeout                                          | 0                                      |
| Ssl_finished_accepts                                         | 0                                      |
| Ssl_finished_connects                                        | 0                                      |
| Ssl_server_not_after                                         |                                        |
| Ssl_server_not_before                                        |                                        |
| Ssl_session_cache_hits                                       | 0                                      |
| Ssl_session_cache_misses                                     | 0                                      |
| Ssl_session_cache_mode                                       | NONE                                   |
| Ssl_session_cache_overflows                                  | 0                                      |
| Ssl_session_cache_size                                       | 0                                      |
| Ssl_session_cache_timeouts                                   | 0                                      |
| Ssl_sessions_reused                                          | 0                                      |
| Ssl_used_session_cache_entries                               | 0                                      |
| Ssl_verify_depth                                             | 0                                      |
| Ssl_verify_mode                                              | 0                                      |
| Ssl_version                                                  |                                        |
| Subquery_cache_hit                                           | 0                                      |
| Subquery_cache_miss                                          | 0                                      |
| Syncs                                                        | 2                                      |
| Table_locks_immediate                                        | 21                                     |
| Table_locks_waited                                           | 0                                      |
| Tc_log_max_pages_used                                        | 0                                      |
| Tc_log_page_size                                             | 4096                                   |
| Tc_log_page_waits                                            | 0                                      |
| Threadpool_idle_threads                                      | 0                                      |
| Threadpool_threads                                           | 0                                      |
| Threads_cached                                               | 0                                      |
| Threads_connected                                            | 1                                      |
| Threads_created                                              | 2                                      |
| Threads_running                                              | 1                                      |
| Update_scan                                                  | 0                                      |
| Uptime                                                       | 223                                    |
| Uptime_since_flush_status                                    | 223                                    |
| wsrep_cluster_conf_id                                        | 18446744073709551615                   |
| wsrep_cluster_size                                           | 0                                      |
| wsrep_cluster_state_uuid                                     |                                        |
| wsrep_cluster_status                                         | Disconnected                           |
| wsrep_connected                                              | OFF                                    |
| wsrep_local_bf_aborts                                        | 0                                      |
| wsrep_local_index                                            | 18446744073709551615                   |
| wsrep_provider_name                                          |                                        |
| wsrep_provider_vendor                                        |                                        |
| wsrep_provider_version                                       |                                        |
| wsrep_ready                                                  | OFF                                    |
| wsrep_thread_count                                           | 0                                      |
+--------------------------------------------------------------+----------------------------------------+
516 rows in set (0.00 sec)

Example of filtered output:

SHOW STATUS LIKE 'Key%';
+------------------------+--------+
| Variable_name          | Value  |
+------------------------+--------+
| Key_blocks_not_flushed | 0      |
| Key_blocks_unused      | 107163 |
| Key_blocks_used        | 0      |
| Key_blocks_warm        | 0      |
| Key_read_requests      | 0      |
| Key_reads              | 0      |
| Key_write_requests     | 0      |
| Key_writes             | 0      |
+------------------------+--------+
8 rows in set (0.00 sec)

1.1.1.2.8.49 SHOW TABLE STATUS

Syntax

SHOW TABLE STATUS [{FROM | IN} db_name]
    [LIKE 'pattern' | WHERE expr]

Contents

  1. Syntax
  2. Description
  3. Views
  4. Example

Description

SHOW TABLE STATUS works like SHOW TABLES, but provides more extensive information about each non-TEMPORARY table.

The LIKE clause, if present on its own, indicates which table names to match. The WHERE and LIKE clauses can be given to select rows using more general conditions, as discussed in Extended SHOW.

The following information is returned:

ColumnDescription
NameTable name.
EngineTable storage engine.
VersionVersion number from the table's .frm file.
Row_formatRow format (see InnoDB, Aria and MyISAM row formats).
RowsNumber of rows in the table. Some engines, such as XtraDB and InnoDB may store an estimate.
Avg_row_lengthAverage row length in the table.
Data_lengthFor InnoDB/XtraDB, the index size, in pages, multiplied by the page size. For Aria and MyISAM, length of the data file, in bytes. For MEMORY, the approximate allocated memory.
Max_data_lengthMaximum length of the data file, ie the total number of bytes that could be stored in the table. Not used in XtraDB and InnoDB.
Index_lengthLength of the index file.
Data_freeBytes allocated but unused. For InnoDB tables in a shared tablespace, the free space of the shared tablespace with small safety margin. An estimate in the case of partitioned tables - see the PARTITIONS table.
Auto_incrementNext AUTO_INCREMENT value.
Create_timeTime the table was created.
Update_timeTime the table was last updated. On Windows, the timestamp is not updated on update, so MyISAM values will be inaccurate. In InnoDB, if shared tablespaces are used, will be NULL, while buffering can also delay the update, so the value will differ from the actual time of the last UPDATE, INSERT or DELETE.
Check_timeTime the table was last checked. Not kept by all storage engines, in which case will be NULL.
CollationCharacter set and collation.
ChecksumLive checksum value, if any.
Create_optionsExtra CREATE TABLE options.
CommentTable comment provided when MariaDB created the table.
Max_index_lengthMaximum index length (supported by MyISAM and Aria tables). Added in MariaDB 10.3.5.
TemporaryPlaceholder to signal that a table is a temporary table. Currently always "N", except "Y" for generated information_schema tables and NULL for views. Added in MariaDB 10.3.5.

Similar information can be found in the information_schema.TABLES table as well as by using mysqlshow:

mysqlshow --status db_name

Views

For views, all columns in SHOW TABLE STATUS are NULL except 'Name' and 'Comment'

Example

show table status\G
*************************** 1. row ***************************
           Name: bus_routes
         Engine: InnoDB
        Version: 10
     Row_format: Dynamic
           Rows: 5
 Avg_row_length: 3276
    Data_length: 16384
Max_data_length: 0
   Index_length: 0
      Data_free: 0
 Auto_increment: NULL
    Create_time: 2017-05-24 11:17:46
    Update_time: NULL
     Check_time: NULL
      Collation: latin1_swedish_ci
       Checksum: NULL
 Create_options: 
        Comment:

1.1.1.2.8.50 SHOW TABLES

Syntax

SHOW [FULL] TABLES [FROM db_name]
    [LIKE 'pattern' | WHERE expr]

Contents

  1. Syntax
  2. Description
  3. Examples
  4. See Also

Description

SHOW TABLES lists the non-TEMPORARY tables, sequences and views in a given database.

The LIKE clause, if present on its own, indicates which table names to match. The WHERE and LIKE clauses can be given to select rows using more general conditions, as discussed in Extended SHOW. For example, when searching for tables in the test database, the column name for use in the WHERE and LIKE clauses will be Tables_in_test

The FULL modifier is supported such that SHOW FULL TABLES displays a second output column. Values for the second column. Table_type, are BASE TABLE for a table, VIEW for a view and SEQUENCE for a sequence.

You can also get this information using:

mysqlshow db_name

See mysqlshow for more details.

If you have no privileges for a base table or view, it does not show up in the output from SHOW TABLES or mysqlshow db_name.

The information_schema.TABLES table, as well as the SHOW TABLE STATUS statement, provide extended information about tables.

Examples

SHOW TABLES;
+----------------------+
| Tables_in_test       |
+----------------------+
| animal_count         |
| animals              |
| are_the_mooses_loose |
| aria_test2           |
| t1                   |
| view1                |
+----------------------+

Showing the tables beginning with a only.

SHOW TABLES WHERE Tables_in_test LIKE 'a%';
+----------------------+
| Tables_in_test       |
+----------------------+
| animal_count         |
| animals              |
| are_the_mooses_loose |
| aria_test2           |
+----------------------+

Showing tables and table types:

SHOW FULL TABLES;
+----------------+------------+
| Tables_in_test | Table_type |
+----------------+------------+
| s1             | SEQUENCE   |
| student        | BASE TABLE |
| v1             | VIEW       |
+----------------+------------+

See Also

1.1.1.2.8.51 SHOW TABLE_STATISTICS

Syntax

SHOW TABLE_STATISTICS

Description

The SHOW TABLE_STATISTICS statementis part of the User Statistics feature. It was removed as a separate statement in MariaDB 10.1.1, but effectively replaced by the generic SHOW information_schema_table statement. The information_schema.TABLE_STATISTICS table shows statistics on table usage

The userstat system variable must be set to 1 to activate this feature. See the User Statistics and information_schema.TABLE_STATISTICS articles for more information.

Example

SHOW TABLE_STATISTICS\G
*************************** 1. row ***************************
           Table_schema: mysql
             Table_name: proxies_priv
              Rows_read: 2
           Rows_changed: 0
Rows_changed_x_#indexes: 0
*************************** 2. row ***************************
           Table_schema: test
             Table_name: employees_example
              Rows_read: 7
           Rows_changed: 0
Rows_changed_x_#indexes: 0
*************************** 3. row ***************************
           Table_schema: mysql
             Table_name: user
              Rows_read: 16
           Rows_changed: 0
Rows_changed_x_#indexes: 0
*************************** 4. row ***************************
           Table_schema: mysql
             Table_name: db
              Rows_read: 2
           Rows_changed: 0
Rows_changed_x_#indexes: 0

1.1.1.2.8.52 SHOW TRIGGERS

Syntax

SHOW TRIGGERS [FROM db_name]
    [LIKE 'pattern' | WHERE expr]

Contents

  1. Syntax
  2. Description
  3. Examples
  4. See also

Description

SHOW TRIGGERS lists the triggers currently defined for tables in a database (the default database unless a FROM clause is given). This statement requires the TRIGGER privilege (prior to MySQL 5.1.22, it required the SUPER privilege).

The LIKE clause, if present on its own, indicates which table names to match and causes the statement to display triggers for those tables. The WHERE and LIKE clauses can be given to select rows using more general conditions, as discussed in Extended SHOW.

Similar information is stored in the information_schema.TRIGGERS table.

MariaDB starting with 10.2.3

If there are multiple triggers for the same action, then the triggers are shown in action order.

Examples

For the trigger defined at Trigger Overview:

SHOW triggers Like 'animals' \G
*************************** 1. row ***************************
             Trigger: the_mooses_are_loose
               Event: INSERT
               Table: animals
           Statement: BEGIN
 IF NEW.name = 'Moose' THEN
  UPDATE animal_count SET animal_count.animals = animal_count.animals+100;
 ELSE 
  UPDATE animal_count SET animal_count.animals = animal_count.animals+1;
 END IF;
END
              Timing: AFTER
             Created: 2016-09-29 13:53:34.35
            sql_mode: 
             Definer: root@localhost
character_set_client: utf8
collation_connection: utf8_general_ci
  Database Collation: latin1_swedish_ci

Listing all triggers associated with a certain table:

SHOW TRIGGERS FROM test WHERE `Table` = 'user' \G
*************************** 1. row ***************************
             Trigger: user_ai
               Event: INSERT
               Table: user
           Statement: BEGIN END
              Timing: AFTER
             Created:  2016-09-29 13:53:34.35
            sql_mode: 
             Definer: root@%
character_set_client: utf8
collation_connection: utf8_general_ci
  Database Collation: latin1_swedish_ci

SHOW triggers WHERE Event Like 'Insert' \G
*************************** 1. row ***************************
             Trigger: the_mooses_are_loose
               Event: INSERT
               Table: animals
           Statement: BEGIN
 IF NEW.name = 'Moose' THEN
  UPDATE animal_count SET animal_count.animals = animal_count.animals+100;
 ELSE 
  UPDATE animal_count SET animal_count.animals = animal_count.animals+1;
 END IF;
END
              Timing: AFTER
             Created: 2016-09-29 13:53:34.35
            sql_mode: 
             Definer: root@localhost
character_set_client: utf8
collation_connection: utf8_general_ci
  Database Collation: latin1_swedish_ci
  • character_set_client is the session value of the character_set_client system variable when the trigger was created.
  • collation_connection is the session value of the collation_connection system variable when the trigger was created.
  • Database Collation is the collation of the database with which the trigger is associated.

These columns were added in MariaDB/MySQL 5.1.21.

Old triggers created before MySQL 5.7 and MariaDB 10.2.3 has NULL in the Created column.

See also

1.1.1.2.8.53 SHOW USER_STATISTICS

Syntax

SHOW USER_STATISTICS

Description

The SHOW USER_STATISTICS statement is part of the User Statistics feature. It was removed as a separate statement in MariaDB 10.1.1, but effectively replaced by the generic SHOW information_schema_table statement. The information_schema.USER_STATISTICS table holds statistics about user activity. You can use this table to find out such things as which user is causing the most load and which users are being abusive. You can also use this table to measure how close to capacity the server may be.

The userstat system variable must be set to 1 to activate this feature. See the User Statistics and information_schema.USER_STATISTICS table for more information.

Example

SHOW USER_STATISTICS\G
*************************** 1. row ***************************
                  User: root
     Total_connections: 1
Concurrent_connections: 0
        Connected_time: 3297
             Busy_time: 0.14113400000000006
              Cpu_time: 0.017637000000000003
        Bytes_received: 969
            Bytes_sent: 22355
  Binlog_bytes_written: 0
             Rows_read: 10
             Rows_sent: 67
          Rows_deleted: 0
         Rows_inserted: 0
          Rows_updated: 0
       Select_commands: 7
       Update_commands: 0
        Other_commands: 0
   Commit_transactions: 1
 Rollback_transactions: 0
    Denied_connections: 0
      Lost_connections: 0
         Access_denied: 0
         Empty_queries: 7

1.1.1.2.8.54 SHOW VARIABLES

Syntax

SHOW [GLOBAL | SESSION] VARIABLES
    [LIKE 'pattern' | WHERE expr]

Contents

  1. Syntax
  2. Description
  3. Examples

Description

SHOW VARIABLES shows the values of MariaDB system variables. This information also can be obtained using the mysqladmin variables command. The LIKE clause, if present, indicates which variable names to match. The WHERE clause can be given to select rows using more general conditions.

With the GLOBAL modifier, SHOW VARIABLES displays the values that are used for new connections to MariaDB. With SESSION, it displays the values that are in effect for the current connection. If no modifier is present, the default is SESSION. LOCAL is a synonym for SESSION. With a LIKE clause, the statement displays only rows for those variables with names that match the pattern. To obtain the row for a specific variable, use a LIKE clause as shown:

SHOW VARIABLES LIKE 'maria_group_commit';
SHOW SESSION VARIABLES LIKE 'maria_group_commit';

To get a list of variables whose name match a pattern, use the "%" wildcard character in a LIKE clause:

SHOW VARIABLES LIKE '%maria%';
SHOW GLOBAL VARIABLES LIKE '%maria%';

Wildcard characters can be used in any position within the pattern to be matched. Strictly speaking, because "_" is a wildcard that matches any single character, you should escape it as "\_" to match it literally. In practice, this is rarely necessary.

The WHERE and LIKE clauses can be given to select rows using more general conditions, as discussed in Extended SHOW.

See SET for information on setting server system variables.

See Server System Variables for a list of all the variables that can be set.

You can also see the server variables by querying the Information Schema GLOBAL_VARIABLES and SESSION_VARIABLES tables.

Examples

SHOW VARIABLES LIKE 'aria%';
+------------------------------------------+---------------------+
| Variable_name                            | Value               |
+------------------------------------------+---------------------+
| aria_block_size                          | 8192                |
| aria_checkpoint_interval                 | 30                  |
| aria_checkpoint_log_activity             | 1048576             |
| aria_force_start_after_recovery_failures | 0                   |
| aria_group_commit                        | none                |
| aria_group_commit_interval               | 0                   |
| aria_log_file_size                       | 1073741824          |
| aria_log_purge_type                      | immediate           |
| aria_max_sort_file_size                  | 9223372036853727232 |
| aria_page_checksum                       | ON                  |
| aria_pagecache_age_threshold             | 300                 |
| aria_pagecache_buffer_size               | 134217728           |
| aria_pagecache_division_limit            | 100                 |
| aria_recover                             | NORMAL              |
| aria_repair_threads                      | 1                   |
| aria_sort_buffer_size                    | 134217728           |
| aria_stats_method                        | nulls_unequal       |
| aria_sync_log_dir                        | NEWFILE             |
| aria_used_for_temp_tables                | ON                  |
+------------------------------------------+---------------------+

SELECT VARIABLE_NAME, SESSION_VALUE, GLOBAL_VALUE FROM
  INFORMATION_SCHEMA.SYSTEM_VARIABLES WHERE
  VARIABLE_NAME LIKE 'max_error_count' OR
  VARIABLE_NAME LIKE 'innodb_sync_spin_loops';
+---------------------------+---------------+--------------+
| VARIABLE_NAME             | SESSION_VALUE | GLOBAL_VALUE |
+---------------------------+---------------+--------------+
| MAX_ERROR_COUNT           | 64            | 64           |
| INNODB_SYNC_SPIN_LOOPS    | NULL          | 30           |
+---------------------------+---------------+--------------+

SET GLOBAL max_error_count=128;

SELECT VARIABLE_NAME, SESSION_VALUE, GLOBAL_VALUE FROM
  INFORMATION_SCHEMA.SYSTEM_VARIABLES WHERE
  VARIABLE_NAME LIKE 'max_error_count' OR
  VARIABLE_NAME LIKE 'innodb_sync_spin_loops';
+---------------------------+---------------+--------------+
| VARIABLE_NAME             | SESSION_VALUE | GLOBAL_VALUE |
+---------------------------+---------------+--------------+
| MAX_ERROR_COUNT           | 64            | 128          |
| INNODB_SYNC_SPIN_LOOPS    | NULL          | 30           |
+---------------------------+---------------+--------------+

SET GLOBAL max_error_count=128;

SHOW VARIABLES LIKE 'max_error_count';
+-----------------+-------+
| Variable_name   | Value |
+-----------------+-------+
| max_error_count | 64    |
+-----------------+-------+

SHOW GLOBAL VARIABLES LIKE 'max_error_count';
+-----------------+-------+
| Variable_name   | Value |
+-----------------+-------+
| max_error_count | 128   |
+-----------------+-------+

Because the following variable only has a global scope, the global value is returned even when specifying SESSION (in this case by default):

SHOW VARIABLES LIKE 'innodb_sync_spin_loops';
+------------------------+-------+
| Variable_name          | Value |
+------------------------+-------+
| innodb_sync_spin_loops | 30    |
+------------------------+-------+

1.1.1.2.8.55 SHOW WARNINGS

Syntax

SHOW WARNINGS [LIMIT [offset,] row_count]
SHOW ERRORS [LIMIT row_count OFFSET offset]
SHOW COUNT(*) WARNINGS

Contents

  1. Syntax
  2. Description
  3. Examples
    1. Stack Trace
  4. See Also

Description

SHOW WARNINGS shows the error, warning, and note messages that resulted from the last statement that generated messages in the current session. It shows nothing if the last statement used a table and generated no messages. (That is, a statement that uses a table but generates no messages clears the message list.) Statements that do not use tables and do not generate messages have no effect on the message list.

A note is different to a warning in that it only appears if the sql_notes variable is set to 1 (the default), and is not converted to an error if strict mode is enabled.

A related statement, SHOW ERRORS, shows only the errors.

The SHOW COUNT(*) WARNINGS statement displays the total number of errors, warnings, and notes. You can also retrieve this number from the warning_count variable:

SHOW COUNT(*) WARNINGS;
SELECT @@warning_count;

The value of warning_count might be greater than the number of messages displayed by SHOW WARNINGS if the max_error_count system variable is set so low that not all messages are stored.

The LIMIT clause has the same syntax as for the SELECT statement.

SHOW WARNINGS can be used after EXPLAIN EXTENDED to see how a query is internally rewritten by MariaDB.

If the sql_notes server variable is set to 1, Notes are included in the output of SHOW WARNINGS; if it is set to 0, this statement will not show (or count) Notes.

The results of SHOW WARNINGS and SHOW COUNT(*) WARNINGS are directly sent to the client. If you need to access those information in a stored program, you can use the GET DIAGNOSTICS statement instead.

For a list of MariaDB error codes, see MariaDB Error Codes.

The mysql client also has a number of options related to warnings. The \W command will show warnings after every statement, while \w will disable this. Starting the client with the --show-warnings option will show warnings after every statement.

MariaDB 10.3.1 implements a stored routine error stack trace. SHOW WARNINGS can also be used to show more information. See the example below.

Examples

SELECT 1/0;
+------+
| 1/0  |
+------+
| NULL |
+------+

SHOW COUNT(*) WARNINGS;
+-------------------------+
| @@session.warning_count |
+-------------------------+
|                       1 |
+-------------------------+

SHOW WARNINGS;
+---------+------+---------------+
| Level   | Code | Message       |
+---------+------+---------------+
| Warning | 1365 | Division by 0 |
+---------+------+---------------+

Stack Trace

From MariaDB 10.3.1, displaying a stack trace:

DELIMITER $$
CREATE OR REPLACE PROCEDURE p1()
  BEGIN
    DECLARE c CURSOR FOR SELECT * FROM not_existing;
    OPEN c;
    CLOSE c;
  END;
$$
CREATE OR REPLACE PROCEDURE p2()
  BEGIN
    CALL p1;
  END;
$$
DELIMITER ;
CALL p2;
ERROR 1146 (42S02): Table 'test.not_existing' doesn't exist

SHOW WARNINGS;
+-------+------+-----------------------------------------+
| Level | Code | Message                                 |
+-------+------+-----------------------------------------+
| Error | 1146 | Table 'test.not_existing' doesn't exist |
| Note  | 4091 | At line 6 in test.p1                    |
| Note  | 4091 | At line 4 in test.p2                    |
+-------+------+-----------------------------------------+

SHOW WARNINGS displays a stack trace, showing where the error actually happened:

  • Line 4 in test.p1 is the OPEN command which actually raised the error
  • Line 3 in test.p2 is the CALL statement, calling p1 from p2.

See Also

1.1.1.2.8.56 SHOW WSREP_MEMBERSHIP

SHOW WSREP_MEMBERSHIP is part of the WSREP_INFO plugin.

Syntax

SHOW WSREP_MEMBERSHIP

Description

The SHOW WSREP_MEMBERSHIP statement returns Galera node cluster membership information. It returns the same information as found in the information_schema.WSREP_MEMBERSHIP table. Only users with the SUPER privilege can access this information.

Examples

SHOW WSREP_MEMBERSHIP;
+-------+--------------------------------------+----------+-----------------+
| Index | Uuid                                 | Name     | Address         |
+-------+--------------------------------------+----------+-----------------+
|     0 | 19058073-8940-11e4-8570-16af7bf8fced | my_node1 | 10.0.2.15:16001 |
|     1 | 19f2b0e0-8942-11e4-9cb8-b39e8ee0b5dd | my_node3 | 10.0.2.15:16003 |
|     2 | d85e62db-8941-11e4-b1ef-4bc9980e476d | my_node2 | 10.0.2.15:16002 |
+-------+--------------------------------------+----------+-----------------+

1.1.1.2.8.57 SHOW WSREP_STATUS

SHOW WSREP_STATUS is part of the WSREP_INFO plugin.

Syntax

SHOW WSREP_STATUS

Description

The SHOW WSREP_STATUS statement returns Galera node and cluster status information. It returns the same information as found in the information_schema.WSREP_STATUS table. Only users with the SUPER privilege can access this information.

Examples

SHOW WSREP_STATUS;
+------------+-------------+----------------+--------------+
| Node_Index | Node_Status | Cluster_Status | Cluster_Size |
+------------+-------------+----------------+--------------+
|          0 | Synced      | Primary        |            3 |
+------------+-------------+----------------+--------------+

1.1.1.2.9 System Tables

1.1.1.2.9.1 Information Schema

Articles about the Information Schema

There are 1 related questions.

1.1.1.2.9.1.1 Information Schema Tables

There are 2 related questions.

1.1.1.2.9.1.1.1 Information Schema InnoDB Tables

List of Information Schema tables specifically related to InnoDB. Tables that are specific to XtraDB shares with InnoDB are listed in Information Schema XtraDB Tables.

1.1.1.2.9.1.1.1.1 Information Schema INNODB_BUFFER_PAGE Table

The Information Schema INNODB_BUFFER_PAGE table contains information about pages in the buffer pool.

The PROCESS privilege is required to view the table.

It has the following columns:

ColumnDescription
POOL_IDBuffer Pool identifier. From MariaDB 10.5.1 returns a value of 0, since multiple InnoDB buffer pool instances has been removed.
BLOCK_IDBuffer Pool Block identifier.
SPACETablespace identifier. Matches the SPACE value in the INNODB_SYS_TABLES table.
PAGE_NUMBERBuffer pool page number.
PAGE_TYPEPage type; one of allocated (newly-allocated page), index (B-tree node), undo_log (undo log page), inode (index node), ibuf_free_list (insert buffer free list), ibuf_bitmap (insert buffer bitmap), system (system page), trx_system (transaction system data), file_space_header (file space header), extent_descriptor (extent descriptor page), blob (uncompressed blob page), compressed_blob (first compressed blob page), compressed_blob2 (subsequent compressed blob page) or unknown.
FLUSH_TYPEFlush type.
FIX_COUNTCount of the threads using this block in the buffer pool. When it is zero, the block can be evicted from the buffer pool.
IS_HASHEDWhether or not a hash index has been built on this page.
NEWEST_MODIFICATIONMost recent modification's Log Sequence Number.
OLDEST_MODIFICATIONOldest modification's Log Sequence Number.
ACCESS_TIMEAbstract number representing the time the page was first accessed.
TABLE_NAMETable that the page belongs to.
INDEX_NAMEIndex that the page belongs to, either a clustered index or a secondary index.
NUMBER_RECORDSNumber of records the page contains.
DATA_SIZESize in bytes of all the records contained in the page.
COMPRESSED_SIZECompressed size in bytes of the page, or NULL for pages that aren't compressed.
PAGE_STATEPage state; one of FILE_PAGE (page from a file) or MEMORY (page from an in-memory object) for valid data, or one of NULL, READY_FOR_USE, NOT_USED, REMOVE_HASH.
IO_FIXWhether there is I/O pending for the page; one of IO_NONE (no pending I/O), IO_READ (read pending), IO_WRITE (write pending).
IS_OLDWhether the page is old or not.
FREE_PAGE_CLOCKFreed_page_clock counter, which tracks the number of blocks removed from the end of the least recently used (LRU) list, at the time the block was last placed at the head of the list.

The related INFORMATION_SCHEMA.INNODB_BUFFER_PAGE_LRU table contains the same information, but with an LRU (least recently used) position rather than block id.

Examples

DESC information_schema.innodb_buffer_page;
+---------------------+---------------------+------+-----+---------+-------+
| Field               | Type                | Null | Key | Default | Extra |
+---------------------+---------------------+------+-----+---------+-------+
| POOL_ID             | bigint(21) unsigned | NO   |     | 0       |       |
| BLOCK_ID            | bigint(21) unsigned | NO   |     | 0       |       |
| SPACE               | bigint(21) unsigned | NO   |     | 0       |       |
| PAGE_NUMBER         | bigint(21) unsigned | NO   |     | 0       |       |
| PAGE_TYPE           | varchar(64)         | YES  |     | NULL    |       |
| FLUSH_TYPE          | bigint(21) unsigned | NO   |     | 0       |       |
| FIX_COUNT           | bigint(21) unsigned | NO   |     | 0       |       |
| IS_HASHED           | varchar(3)          | YES  |     | NULL    |       |
| NEWEST_MODIFICATION | bigint(21) unsigned | NO   |     | 0       |       |
| OLDEST_MODIFICATION | bigint(21) unsigned | NO   |     | 0       |       |
| ACCESS_TIME         | bigint(21) unsigned | NO   |     | 0       |       |
| TABLE_NAME          | varchar(1024)       | YES  |     | NULL    |       |
| INDEX_NAME          | varchar(1024)       | YES  |     | NULL    |       |
| NUMBER_RECORDS      | bigint(21) unsigned | NO   |     | 0       |       |
| DATA_SIZE           | bigint(21) unsigned | NO   |     | 0       |       |
| COMPRESSED_SIZE     | bigint(21) unsigned | NO   |     | 0       |       |
| PAGE_STATE          | varchar(64)         | YES  |     | NULL    |       |
| IO_FIX              | varchar(64)         | YES  |     | NULL    |       |
| IS_OLD              | varchar(3)          | YES  |     | NULL    |       |
| FREE_PAGE_CLOCK     | bigint(21) unsigned | NO   |     | 0       |       |
+---------------------+---------------------+------+-----+---------+-------+

SELECT * FROM INFORMATION_SCHEMA.INNODB_BUFFER_PAGE\G
...
*************************** 6. row ***************************
            POOL_ID: 0
           BLOCK_ID: 5
              SPACE: 0
        PAGE_NUMBER: 11
          PAGE_TYPE: INDEX
         FLUSH_TYPE: 1
          FIX_COUNT: 0
          IS_HASHED: NO
NEWEST_MODIFICATION: 2046835
OLDEST_MODIFICATION: 0
        ACCESS_TIME: 2585566280
         TABLE_NAME: `SYS_INDEXES`
         INDEX_NAME: CLUST_IND
     NUMBER_RECORDS: 57
          DATA_SIZE: 4016
    COMPRESSED_SIZE: 0
         PAGE_STATE: FILE_PAGE
             IO_FIX: IO_NONE
             IS_OLD: NO
    FREE_PAGE_CLOCK: 0
...

1.1.1.2.9.1.1.1.2 Information Schema INNODB_BUFFER_PAGE_LRU Table

The Information Schema INNODB_BUFFER_PAGE_LRU table contains information about pages in the buffer pool and how they are ordered for eviction purposes.

The PROCESS privilege is required to view the table.

It has the following columns:

ColumnDescription
POOL_IDBuffer Pool identifier. From MariaDB 10.5.1 returns a value of 0, since multiple InnoDB buffer pool instances has been removed.
LRU_POSITIONLRU (Least recently-used), for determining eviction order from the buffer pool.
SPACETablespace identifier. Matches the SPACE value on the INNODB_SYS_TABLES table.
PAGE_NUMBERBuffer pool page number.
PAGE_TYPEPage type; one of allocated (newly-allocated page), index (B-tree node), undo_log (undo log page), inode (index node), ibuf_free_list (insert buffer free list), ibuf_bitmap (insert buffer bitmap), system (system page), trx_system (transaction system data), file_space_header (file space header), extent_descriptor (extent descriptor page), blob (uncompressed blob page), compressed_blob (first compressed blob page), compressed_blob2 (subsequent compressed blob page) or unknown.
FLUSH_TYPEFlush type.
FIX_COUNTCount of the threads using this block in the buffer pool. When it is zero, the block can be evicted from the buffer pool.
IS_HASHEDWhether or not a hash index has been built on this page.
NEWEST_MODIFICATIONMost recent modification's Log Sequence Number.
OLDEST_MODIFICATIONOldest modification's Log Sequence Number.
ACCESS_TIMEAbstract number representing the time the page was first accessed.
TABLE_NAMETable that the page belongs to.
INDEX_NAMEIndex that the page belongs to, either a clustered index or a secondary index.
NUMBER_RECORDSNumber of records the page contains.
DATA_SIZESize in bytes of all the records contained in the page.
COMPRESSED_SIZECompressed size in bytes of the page, or NULL for pages that aren't compressed.
PAGE_STATEPage state; one of FILE_PAGE (page from a file) or MEMORY (page from an in-memory object) for valid data, or one of NULL, READY_FOR_USE, NOT_USED, REMOVE_HASH.
IO_FIXWhether there is I/O pending for the page; one of IO_NONE (no pending I/O), IO_READ (read pending), IO_WRITE (write pending).
IS_OLDWhether the page is old or not.
FREE_PAGE_CLOCKFreed_page_clock counter, which tracks the number of blocks removed from the end of the LRU list, at the time the block was last placed at the head of the list.

The related INFORMATION_SCHEMA.INNODB_BUFFER_PAGE table contains the same information, but with a block id rather than LRU position.

Example

DESC information_schema.innodb_buffer_page_lru;
+---------------------+---------------------+------+-----+---------+-------+
| Field               | Type                | Null | Key | Default | Extra |
+---------------------+---------------------+------+-----+---------+-------+
| POOL_ID             | bigint(21) unsigned | NO   |     | 0       |       |
| LRU_POSITION        | bigint(21) unsigned | NO   |     | 0       |       |
| SPACE               | bigint(21) unsigned | NO   |     | 0       |       |
| PAGE_NUMBER         | bigint(21) unsigned | NO   |     | 0       |       |
| PAGE_TYPE           | varchar(64)         | YES  |     | NULL    |       |
| FLUSH_TYPE          | bigint(21) unsigned | NO   |     | 0       |       |
| FIX_COUNT           | bigint(21) unsigned | NO   |     | 0       |       |
| IS_HASHED           | varchar(3)          | YES  |     | NULL    |       |
| NEWEST_MODIFICATION | bigint(21) unsigned | NO   |     | 0       |       |
| OLDEST_MODIFICATION | bigint(21) unsigned | NO   |     | 0       |       |
| ACCESS_TIME         | bigint(21) unsigned | NO   |     | 0       |       |
| TABLE_NAME          | varchar(1024)       | YES  |     | NULL    |       |
| INDEX_NAME          | varchar(1024)       | YES  |     | NULL    |       |
| NUMBER_RECORDS      | bigint(21) unsigned | NO   |     | 0       |       |
| DATA_SIZE           | bigint(21) unsigned | NO   |     | 0       |       |
| COMPRESSED_SIZE     | bigint(21) unsigned | NO   |     | 0       |       |
| COMPRESSED          | varchar(3)          | YES  |     | NULL    |       |
| IO_FIX              | varchar(64)         | YES  |     | NULL    |       |
| IS_OLD              | varchar(3)          | YES  |     | NULL    |       |
| FREE_PAGE_CLOCK     | bigint(21) unsigned | NO   |     | 0       |       |
+---------------------+---------------------+------+-----+---------+-------+

SELECT * FROM INFORMATION_SCHEMA.INNODB_BUFFER_PAGE_LRU\G
...
*************************** 6. row ***************************
            POOL_ID: 0
       LRU_POSITION: 5
              SPACE: 0
        PAGE_NUMBER: 11
          PAGE_TYPE: INDEX
         FLUSH_TYPE: 1
          FIX_COUNT: 0
          IS_HASHED: NO
NEWEST_MODIFICATION: 2046835
OLDEST_MODIFICATION: 0
        ACCESS_TIME: 2585566280
         TABLE_NAME: `SYS_INDEXES`
         INDEX_NAME: CLUST_IND
     NUMBER_RECORDS: 57
          DATA_SIZE: 4016
    COMPRESSED_SIZE: 0
         COMPRESSED: NO
             IO_FIX: IO_NONE
             IS_OLD: NO
    FREE_PAGE_CLOCK: 0
...

1.1.1.2.9.1.1.1.3 Information Schema INNODB_BUFFER_POOL_PAGES Table

The Information Schema INNODB_BUFFER_POOL_PAGES table is a Percona enhancement, and is only available for XtraDB, not InnoDB (see XtraDB and InnoDB). It contains a record for each page in the buffer pool.

It has the following columns:

ColumnDescription
PAGE_TYPEType of page; one of index, undo_log, inode, ibuf_free_list, allocated, bitmap, sys, trx_sys, fsp_hdr, xdes, blob, zblob, zblob2 and unknown.
SPACE_IDTablespace ID.
PAGE_NOPage offset within tablespace.
LRU_POSITIONPage position in the LRU (least-recently-used) list.
FIX_COUNTPage reference count, incremented each time the page is accessed. 0 if the page is not currently being accessed.
FLUSH_TYPEFlush type of the most recent flush.0 (LRU), 2 (flush_list)

1.1.1.2.9.1.1.1.4 Information Schema INNODB_BUFFER_POOL_PAGES_BLOB Table

The Information Schema INNODB_BUFFER_POOL_PAGES_BLOB table is a Percona enchancement, and is only available for XtraDB, not InnoDB (see XtraDB and InnoDB). It contains information about buffer pool blob pages.

It has the following columns:

ColumnDescription
SPACE_IDTablespace ID.
PAGE_NOPage offset within tablespace.
COMPRESSED1 if the blob contains compressed data, 0 if not.
PART_LENPage data length.
NEXT_PAGE_NONext page number.
LRU_POSITIONPage position in the LRU (least-recently-used) list.
FIX_COUNTPage reference count, incremented each time the page is accessed. 0 if the page is not currently being accessed.
FLUSH_TYPEFlush type of the most recent flush.0 (LRU), 2 (flush_list)

1.1.1.2.9.1.1.1.5 Information Schema INNODB_BUFFER_POOL_PAGES_INDEX Table

The Information Schema INNODB_BUFFER_POOL_PAGES table is a Percona enhancement, and is only available for XtraDB, not InnoDB (see XtraDB and InnoDB). It contains information about buffer pool index pages.

It has the following columns:

ColumnDescription
INDEX_IDIndex name
SPACE_IDTablespace ID
PAGE_NOPage offset within tablespace.
N_RECSNumber of user records on the page.
DATA_SIZETotal data size in bytes of records in the page.
HASHED1 if the block is in the adaptive hash index, 0 if not.
ACCESS_TIMEPage's last access time.
MODIFIED1 if the page has been modified since being loaded, 0 if not.
DIRTY1 if the page has been modified since it was last flushed, 0 if not
OLD1 if the page in the in the old blocks of the LRU (least-recently-used) list, 0 if not.
LRU_POSITIONPosition in the LRU (least-recently-used) list.
FIX_COUNTPage reference count, incremented each time the page is accessed. 0 if the page is not currently being accessed.
FLUSH_TYPEFlush type of the most recent flush.0 (LRU), 2 (flush_list)

1.1.1.2.9.1.1.1.6 Information Schema INNODB_BUFFER_POOL_STATS Table

The Information Schema INNODB_BUFFER_POOL_STATS table contains information about pages in the buffer pool, similar to what is returned with the SHOW ENGINE INNODB STATUS statement.

The PROCESS privilege is required to view the table.

It has the following columns:

ColumnDescription
POOL_IDBuffer Pool identifier. From MariaDB 10.5.1 returns a value of 0, since multiple InnoDB buffer pool instances has been removed.
POOL_SIZESize in pages of the buffer pool.
FREE_BUFFERSNumber of free pages in the buffer pool.
DATABASE_PAGESTotal number of pages in the buffer pool.
OLD_DATABASE_PAGESNumber of pages in the old sublist.
MODIFIED_DATABASE_PAGESNumber of dirty pages.
PENDING_DECOMPRESSNumber of pages pending decompression.
PENDING_READSPending buffer pool level reads.
PENDING_FLUSH_LRUNumber of pages in the LRU pending flush.
PENDING_FLUSH_LISTNumber of pages in the flush list pending flush.
PAGES_MADE_YOUNGPages moved from the old sublist to the new sublist.
PAGES_NOT_MADE_YOUNGPages that have remained in the old sublist without moving to the new sublist.
PAGES_MADE_YOUNG_RATEHits that cause blocks to move to the top of the new sublist.
PAGES_MADE_NOT_YOUNG_RATEHits that do not cause blocks to move to the top of the new sublist due to the innodb_old_blocks delay not being met.
NUMBER_PAGES_READNumber of pages read.
NUMBER_PAGES_CREATEDNumber of pages created.
NUMBER_PAGES_WRITTENNumber of pages written.
PAGES_READ_RATENumber of pages read since the last printout divided by the time elapsed, giving pages read per second.
PAGES_CREATE_RATENumber of pages created since the last printout divided by the time elapsed, giving pages created per second.
PAGES_WRITTEN_RATENumber of pages written since the last printout divided by the time elapsed, giving pages written per second.
NUMBER_PAGES_GETNumber of logical read requests.
HIT_RATEBuffer pool hit rate.
YOUNG_MAKE_PER_THOUSAND_GETSFor every 1000 gets, the number of pages made young.
NOT_YOUNG_MAKE_PER_THOUSAND_GETSFor every 1000 gets, the number of pages not made young.
NUMBER_PAGES_READ_AHEADNumber of pages read ahead.
NUMBER_READ_AHEAD_EVICTEDNumber of pages read ahead by the read-ahead thread that were later evicted without being accessed by any queries.
READ_AHEAD_RATEPages read ahead since the last printout divided by the time elapsed, giving read-ahead rate per second.
READ_AHEAD_EVICTED_RATERead-ahead pages not accessed since the last printout divided by time elapsed, giving the number of read-ahead pages evicted without access per second.
LRU_IO_TOTALTotal least-recently used I/O.
LRU_IO_CURRENTLeast-recently used I/O for the current interval.
UNCOMPRESS_TOTALTotal number of pages decompressed.
UNCOMPRESS_CURRENTNumber of pages decompressed in the current interval

Examples

DESC information_schema.innodb_buffer_pool_stats;
+----------------------------------+---------------------+------+-----+---------+-------+
| Field                            | Type                | Null | Key | Default | Extra |
+----------------------------------+---------------------+------+-----+---------+-------+
| POOL_ID                          | bigint(21) unsigned | NO   |     | 0       |       |
| POOL_SIZE                        | bigint(21) unsigned | NO   |     | 0       |       |
| FREE_BUFFERS                     | bigint(21) unsigned | NO   |     | 0       |       |
| DATABASE_PAGES                   | bigint(21) unsigned | NO   |     | 0       |       |
| OLD_DATABASE_PAGES               | bigint(21) unsigned | NO   |     | 0       |       |
| MODIFIED_DATABASE_PAGES          | bigint(21) unsigned | NO   |     | 0       |       |
| PENDING_DECOMPRESS               | bigint(21) unsigned | NO   |     | 0       |       |
| PENDING_READS                    | bigint(21) unsigned | NO   |     | 0       |       |
| PENDING_FLUSH_LRU                | bigint(21) unsigned | NO   |     | 0       |       |
| PENDING_FLUSH_LIST               | bigint(21) unsigned | NO   |     | 0       |       |
| PAGES_MADE_YOUNG                 | bigint(21) unsigned | NO   |     | 0       |       |
| PAGES_NOT_MADE_YOUNG             | bigint(21) unsigned | NO   |     | 0       |       |
| PAGES_MADE_YOUNG_RATE            | double              | NO   |     | 0       |       |
| PAGES_MADE_NOT_YOUNG_RATE        | double              | NO   |     | 0       |       |
| NUMBER_PAGES_READ                | bigint(21) unsigned | NO   |     | 0       |       |
| NUMBER_PAGES_CREATED             | bigint(21) unsigned | NO   |     | 0       |       |
| NUMBER_PAGES_WRITTEN             | bigint(21) unsigned | NO   |     | 0       |       |
| PAGES_READ_RATE                  | double              | NO   |     | 0       |       |
| PAGES_CREATE_RATE                | double              | NO   |     | 0       |       |
| PAGES_WRITTEN_RATE               | double              | NO   |     | 0       |       |
| NUMBER_PAGES_GET                 | bigint(21) unsigned | NO   |     | 0       |       |
| HIT_RATE                         | bigint(21) unsigned | NO   |     | 0       |       |
| YOUNG_MAKE_PER_THOUSAND_GETS     | bigint(21) unsigned | NO   |     | 0       |       |
| NOT_YOUNG_MAKE_PER_THOUSAND_GETS | bigint(21) unsigned | NO   |     | 0       |       |
| NUMBER_PAGES_READ_AHEAD          | bigint(21) unsigned | NO   |     | 0       |       |
| NUMBER_READ_AHEAD_EVICTED        | bigint(21) unsigned | NO   |     | 0       |       |
| READ_AHEAD_RATE                  | double              | NO   |     | 0       |       |
| READ_AHEAD_EVICTED_RATE          | double              | NO   |     | 0       |       |
| LRU_IO_TOTAL                     | bigint(21) unsigned | NO   |     | 0       |       |
| LRU_IO_CURRENT                   | bigint(21) unsigned | NO   |     | 0       |       |
| UNCOMPRESS_TOTAL                 | bigint(21) unsigned | NO   |     | 0       |       |
| UNCOMPRESS_CURRENT               | bigint(21) unsigned | NO   |     | 0       |       |
+----------------------------------+---------------------+------+-----+---------+-------+

1.1.1.2.9.1.1.1.7 Information Schema INNODB_CHANGED_PAGES Table

The Information Schema INNODB_CHANGED_PAGES Table contains data about modified pages from the bitmap file. It is updated at checkpoints by the log tracking thread parsing the log, so does not contain real-time data.

The number of records is limited by the value of the innodb_max_changed_pages system variable.

The PROCESS privilege is required to view the table.

It has the following columns:

ColumnDescription
SPACE_IDModified page space id
PAGE_IDModified page id
START_LSNInterval start after which page was changed (equal to checkpoint LSN)
END_LSNInterval end before which page was changed (equal to checkpoint LSN)

1.1.1.2.9.1.1.1.8 Information Schema INNODB_CMP and INNODB_CMP_RESET Tables

The INNODB_CMP and INNODB_CMP_RESET tables contain status information on compression operations related to compressed XtraDB/InnoDB tables.

The PROCESS privilege is required to query this table.

These tables contain the following columns:

Column NameDescription
PAGE_SIZECompressed page size, in bytes. This value is unique in the table; other values are totals which refer to pages of this size.
COMPRESS_OPSHow many times a page of the size PAGE_SIZE has been compressed. This happens when a new page is created because the compression log runs out of space. This value includes both successful operations and compression failures.
COMPRESS_OPS_OKHow many times a page of the size PAGE_SIZE has been successfully compressed. This value should be as close as possible to COMPRESS_OPS. If it is notably lower, either avoid compressing some tables, or increase the KEY_BLOCK_SIZE for some compressed tables.
COMPRESS_TIMETime (in seconds) spent to compress pages of the size PAGE_SIZE. This value includes time spent in compression failures.
UNCOMPRESS_OPSHow many times a page of the size PAGE_SIZE has been uncompressed. This happens when an uncompressed version of a page is created in the buffer pool, or when a compression failure occurs.
UNCOMPRESS_TIMETime (in seconds) spent to uncompress pages of the size PAGE_SIZE.

These tables can be used to measure the effectiveness of XtraDB/InnoDB table compression. When you have to decide a value for KEY_BLOCK_SIZE, you can create more than one version of the table (one for each candidate value) and run a realistic workload on them. Then, these tables can be used to see how the operations performed with different page sizes.

INNODB_CMP and INNODB_CMP_RESET have the same columns and always contain the same values, but when INNODB_CMP_RESET is queried, both the tables are cleared. INNODB_CMP_RESET can be used, for example, if a script periodically logs the performances of compression in the last period of time. INNODB_CMP can be used to see the cumulated statistics.

Examples

SELECT * FROM information_schema.INNODB_CMP\G
**************************** 1. row *****************************
      page_size: 1024
   compress_ops: 0
compress_ops_ok: 0
  compress_time: 0
 uncompress_ops: 0
uncompress_time: 0
...

See Also

Other tables that can be used to monitor XtraDB/InnoDB compressed tables:

1.1.1.2.9.1.1.1.9 Information Schema INNODB_CMPMEM and INNODB_CMPMEM_RESET Tables

The INNODB_CMPMEM and INNODB_CMPMEM_RESET tables contain status information on compressed pages in the buffer pool (see InnoDB COMPRESSED format).

The PROCESS privilege is required to query this table.

These tables contain the following columns:

Column NameDescription
PAGE_SIZECompressed page size, in bytes. This value is unique in the table; other values are totals which refer to pages of this size.
BUFFER_POOL_INSTANCEBuffer Pool identifier. From MariaDB 10.5.1 returns a value of 0, since multiple InnoDB buffer pool instances has been removed.
PAGES_USEDNumber of pages of the size PAGE_SIZE which are currently in the buffer pool.
PAGES_FREENumber of pages of the size PAGE_SIZE which are currently free, and thus are available for allocation. This value represents the buffer pool's fragmentation. A totally unfragmented buffer pool has at most 1 free page.
RELOCATION_OPSHow many times a page of the size PAGE_SIZE has been relocated. This happens when data exceeds a page (because a row must be copied into a new page) and when two pages are merged (because their data shrunk and can now be contained in one page).
RELOCATION_TIMETime (in seconds) spent in relocation operations for pages of the size PAGE_SIZE. This column is reset when the INNODB_CMPMEM_RESET table is queried.

These tables can be used to measure the effectiveness of InnoDB table compression. When you have to decide a value for KEY_BLOCK_SIZE, you can create more than one version of the table (one for each candidate value) and run a realistic workload on them. Then, these tables can be used to see how the operations performed with different page sizes.

INNODB_CMPMEM and INNODB_CMPMEM_RESET have the same columns and always contain the same values, but when INNODB_CMPMEM_RESET is queried, the RELOCATION_TIME column from both the tables are cleared. INNODB_CMPMEM_RESET can be used, for example, if a script periodically logs the performances of compression in the last period of time. INNODB_CMPMEM can be used to see the cumulated statistics.

Example

SELECT * FROM information_schema.INNODB_CMPMEM\G
********************** 1. row **********************
            page_size: 1024
 buffer_pool_instance: 0
           pages_used: 0
           pages_free: 0
      reloacation_ops: 0
      relocation_time: 0

See Also

Other tables that can be used to monitor InnoDB compressed tables:

1.1.1.2.9.1.1.1.10 Information Schema INNODB_CMP_PER_INDEX and INNODB_CMP_PER_INDEX_RESET Tables

The INNODB_CMP_PER_INDEX and INNODB_CMP_PER_INDEX_RESET tables contain status information on compression operations related to compressed XtraDB/InnoDB tables, grouped by individual indexes. These tables are only populated if the innodb_cmp_per_index_enabled system variable is set to ON.

The PROCESS privilege is required to query this table.

These tables contains the following columns:

Column NameDescription
DATABASE_NAMEDatabase containing the index.
TABLE_NAMETable containing the index.
INDEX_NAMEOther values are totals which refer to this index's compression.
COMPRESS_OPSHow many times a page of INDEX_NAME has been compressed. This happens when a new page is created because the compression log runs out of space. This value includes both successful operations and compression failures.
COMPRESS_OPS_OKHow many times a page of INDEX_NAME has been successfully compressed. This value should be as close as possible to COMPRESS_OPS. If it is notably lower, either avoid compressing some tables, or increase the KEY_BLOCK_SIZE for some compressed tables.
COMPRESS_TIMETime (in seconds) spent to compress pages of the size PAGE_SIZE. This value includes time spent in compression failures.
UNCOMPRESS_OPSHow many times a page of INDEX_NAME has been uncompressed. This happens when an uncompressed version of a page is created in the buffer pool, or when a compression failure occurs.
UNCOMPRESS_TIMETime (in seconds) spent to uncompress pages of INDEX_NAME.

These tables can be used to measure the effectiveness of XtraDB/InnoDB compression, per table or per index. The values in these tables show which tables perform better with index compression, and which tables cause too many compression failures or perform too many compression/uncompression operations. When compression performs badly for a table, this might mean that you should change its KEY_BLOCK_SIZE, or that the table should not be compressed.

INNODB_CMP_PER_INDEX and INNODB_CMP_PER_INDEX_RESET have the same columns and always contain the same values, but when INNODB_CMP_PER_INDEX_RESET is queried, both the tables are cleared. INNODB_CMP_PER_INDEX_RESET can be used, for example, if a script periodically logs the performances of compression in the last period of time. INNODB_CMP_PER_INDEX can be used to see the cumulated statistics.

See Also

Other tables that can be used to monitor XtraDB/InnoDB compressed tables:

1.1.1.2.9.1.1.1.11 Information Schema INNODB_FT_BEING_DELETED Table

The Information Schema INNODB_FT_BEING_DELETED table is only used while document ID's in the related INNODB_FT_DELETED are being removed from an InnoDB fulltext index while an OPTIMIZE TABLE is underway. At all other times the table will be empty.

The SUPER privilege is required to view the table, and it also requires the innodb_ft_aux_table system variable to be set.

It has the following column:

ColumnDescription
DOC_IDDocument ID of the row being deleted. Either an underlying ID value, or a sequence value generated by InnoDB if no usable option exists.

1.1.1.2.9.1.1.1.12 Information Schema INNODB_FT_CONFIG Table

The Information Schema INNODB_FT_CONFIG table contains InnoDB fulltext index metadata.

The SUPER privilege is required to view the table, and it also requires the innodb_ft_aux_table system variable to be set.

It has the following columns:

ColumnDescription
KEYMetadata item name.
VALUEAssociated value.

Example

SELECT * FROM INNODB_FT_CONFIG;
+---------------------------+-------+
| KEY                       | VALUE |
+---------------------------+-------+
| optimize_checkpoint_limit | 180   |
| synced_doc_id             | 6     |
| last_optimized_word       |       |
| deleted_doc_count         | 0     |
| total_word_count          |       |
| optimize_start_time       |       |
| optimize_end_time         |       |
| stopword_table_name       |       |
| use_stopword              | 1     |
| table_state               | 0     |
+---------------------------+-------+

1.1.1.2.9.1.1.1.13 Information Schema INNODB_FT_DEFAULT_STOPWORD Table

The Information Schema INNODB_FT_DEFAULT_STOPWORD table contains a list of default stopwords used when creating an InnoDB fulltext index.

The PROCESS privilege is required to view the table.

It has the following column:

ColumnDescription
VALUEDefault stopword for an InnoDB fulltext index. Setting either the innodb_ft_server_stopword_table or the innodb_ft_user_stopword_table system variable will override this.

Example

SELECT * FROM information_schema.INNODB_FT_DEFAULT_STOPWORD\G
*************************** 1. row ***************************
value: a
*************************** 2. row ***************************
value: about
*************************** 3. row ***************************
value: an
*************************** 4. row ***************************
value: are
...
*************************** 36. row ***************************
value: www

1.1.1.2.9.1.1.1.14 Information Schema INNODB_FT_DELETED Table

The Information Schema INNODB_FT_DELETED table contains rows that have been deleted from an InnoDB fulltext index. This information is then used to filter results on subsequent searches, removing the need to expensively reorganise the index each time a row is deleted.

The fulltext index is then only reorganized when an OPTIMIZE TABLE statement is underway. The related INNODB_FT_BEING_DELETED table contains rows being deleted while an OPTIMIZE TABLE is in the process of running.

The SUPER privilege is required to view the table, and it also requires the innodb_ft_aux_table system variable to be set.

It has the following column:

ColumnDescription
DOC_IDDocument ID of the deleted row deleted. Either an underlying ID value, or a sequence value generated by InnoDB if no usable option exists.

Example

SELECT * FROM INFORMATION_SCHEMA.INNODB_FT_DELETED;
+--------+
| DOC_ID |
+--------+
|      2 |
+--------+

DELETE FROM test.ft_innodb LIMIT 1;

SELECT * FROM INFORMATION_SCHEMA.INNODB_FT_DELETED;
+--------+
| DOC_ID |
+--------+
|      2 |
|      3 |
+--------+

1.1.1.2.9.1.1.1.15 Information Schema INNODB_FT_INDEX_CACHE Table

The Information Schema INNODB_FT_INDEX_CACHE table contains information about rows that have recently been inserted into an InnoDB fulltext index. To avoid re-organizing the fulltext index each time a change is made, which would be very expensive, new changes are stored separately and only integrated when an OPTIMIZE TABLE is run.

The SUPER privilege is required to view the table, and it also requires the innodb_ft_aux_table system variable to be set.

It has the following columns:

ColumnDescription
WORDWord from the text of a newly added row. Words can appear multiple times in the table, once per DOC_ID and POSITION combination.
FIRST_DOC_IDFirst document ID where this word appears in the index.
LAST_DOC_IDLast document ID where this word appears in the index.
DOC_COUNTNumber of rows containing this word in the index.
DOC_IDDocument ID of the newly added row, either an appropriate ID column or an internal InnoDB value.
POSITIONPosition of this word instance within the DOC_ID, as an offset added to the previous POSITION instance.

Note that for OPTIMIZE TABLE to process InnoDB fulltext index data, the innodb_optimize_fulltext_only system variable needs to be set to 1. When this is done, and an OPTIMIZE TABLE statement run, the INNODB_FT_INDEX_CACHE table will be emptied, and the INNODB_FT_INDEX_TABLE table will be updated.

Examples

SELECT * FROM INNODB_FT_INDEX_CACHE;
+------------+--------------+-------------+-----------+--------+----------+
| WORD       | FIRST_DOC_ID | LAST_DOC_ID | DOC_COUNT | DOC_ID | POSITION |
+------------+--------------+-------------+-----------+--------+----------+
| and        |            4 |           4 |         1 |      4 |        0 |
| arrived    |            4 |           4 |         1 |      4 |       20 |
| ate        |            1 |           1 |         1 |      1 |        4 |
| everybody  |            1 |           1 |         1 |      1 |        8 |
| goldilocks |            4 |           4 |         1 |      4 |        9 |
| hungry     |            3 |           3 |         1 |      3 |        8 |
| then       |            4 |           4 |         1 |      4 |        4 |
| wicked     |            2 |           2 |         1 |      2 |        4 |
| witch      |            2 |           2 |         1 |      2 |       11 |
+------------+--------------+-------------+-----------+--------+----------+
9 rows in set (0.00 sec)

INSERT INTO test.ft_innodb VALUES(3,'And she ate a pear');

SELECT * FROM INNODB_FT_INDEX_CACHE;
+------------+--------------+-------------+-----------+--------+----------+
| WORD       | FIRST_DOC_ID | LAST_DOC_ID | DOC_COUNT | DOC_ID | POSITION |
+------------+--------------+-------------+-----------+--------+----------+
| and        |            4 |           5 |         2 |      4 |        0 |
| and        |            4 |           5 |         2 |      5 |        0 |
| arrived    |            4 |           4 |         1 |      4 |       20 |
| ate        |            1 |           5 |         2 |      1 |        4 |
| ate        |            1 |           5 |         2 |      5 |        8 |
| everybody  |            1 |           1 |         1 |      1 |        8 |
| goldilocks |            4 |           4 |         1 |      4 |        9 |
| hungry     |            3 |           3 |         1 |      3 |        8 |
| pear       |            5 |           5 |         1 |      5 |       14 |
| she        |            5 |           5 |         1 |      5 |        4 |
| then       |            4 |           4 |         1 |      4 |        4 |
| wicked     |            2 |           2 |         1 |      2 |        4 |
| witch      |            2 |           2 |         1 |      2 |       11 |
+------------+--------------+-------------+-----------+--------+----------+

OPTIMIZE TABLE test.ft_innodb\G
*************************** 1. row ***************************
   Table: test.ft_innodb
      Op: optimize
Msg_type: note
Msg_text: Table does not support optimize, doing recreate + analyze instead
*************************** 2. row ***************************
   Table: test.ft_innodb
      Op: optimize
Msg_type: status
Msg_text: OK
2 rows in set (2.24 sec)

SELECT * FROM INNODB_FT_INDEX_CACHE;
+------------+--------------+-------------+-----------+--------+----------+
| WORD       | FIRST_DOC_ID | LAST_DOC_ID | DOC_COUNT | DOC_ID | POSITION |
+------------+--------------+-------------+-----------+--------+----------+
| and        |            4 |           5 |         2 |      4 |        0 |
| and        |            4 |           5 |         2 |      5 |        0 |
| arrived    |            4 |           4 |         1 |      4 |       20 |
| ate        |            1 |           5 |         2 |      1 |        4 |
| ate        |            1 |           5 |         2 |      5 |        8 |
| everybody  |            1 |           1 |         1 |      1 |        8 |
| goldilocks |            4 |           4 |         1 |      4 |        9 |
| hungry     |            3 |           3 |         1 |      3 |        8 |
| pear       |            5 |           5 |         1 |      5 |       14 |
| she        |            5 |           5 |         1 |      5 |        4 |
| then       |            4 |           4 |         1 |      4 |        4 |
| wicked     |            2 |           2 |         1 |      2 |        4 |
| witch      |            2 |           2 |         1 |      2 |       11 |
+------------+--------------+-------------+-----------+--------+----------+
13 rows in set (0.00 sec)

The OPTIMIZE TABLE statement has no effect, because the innodb_optimize_fulltext_only variable wasn't set:

SHOW VARIABLES LIKE 'innodb_optimize_fulltext_only';
+-------------------------------+-------+
| Variable_name                 | Value |
+-------------------------------+-------+
| innodb_optimize_fulltext_only | OFF   |
+-------------------------------+-------+

SET GLOBAL innodb_optimize_fulltext_only =1;

OPTIMIZE TABLE test.ft_innodb;
+----------------+----------+----------+----------+
| Table          | Op       | Msg_type | Msg_text |
+----------------+----------+----------+----------+
| test.ft_innodb | optimize | status   | OK       |
+----------------+----------+----------+----------+

SELECT * FROM INNODB_FT_INDEX_CACHE;
Empty set (0.00 sec)

1.1.1.2.9.1.1.1.16 Information Schema INNODB_FT_INDEX_TABLE Table

The Information Schema INNODB_FT_INDEX_TABLE table contains information about InnoDB fulltext indexes. To avoid re-organizing the fulltext index each time a change is made, which would be very expensive, new changes are stored separately and only integrated when an OPTIMIZE TABLE is run. See the INNODB_FT_INDEX_CACHE table.

The SUPER privilege is required to view the table, and it also requires the innodb_ft_aux_table system variable to be set.

It has the following columns:

ColumnDescription
WORDWord from the text of a column with a fulltext index. Words can appear multiple times in the table, once per DOC_ID and POSITION combination.
FIRST_DOC_IDFirst document ID where this word appears in the index.
LAST_DOC_IDLast document ID where this word appears in the index.
DOC_COUNTNumber of rows containing this word in the index.
DOC_IDDocument ID of the newly added row, either an appropriate ID column or an internal InnoDB value.
POSITIONPosition of this word instance within the DOC_ID, as an offset added to the previous POSITION instance.

Note that for OPTIMIZE TABLE to process InnoDB fulltext index data, the innodb_optimize_fulltext_only system variable needs to be set to 1. When this is done, and an OPTIMIZE TABLE statement run, the INNODB_FT_INDEX_CACHE table will be emptied, and the INNODB_FT_INDEX_TABLE table will be updated.

Examples

SELECT * FROM INNODB_FT_INDEX_TABLE;
Empty set (0.00 sec)

SET GLOBAL innodb_optimize_fulltext_only =1;

OPTIMIZE TABLE test.ft_innodb;
+----------------+----------+----------+----------+
| Table          | Op       | Msg_type | Msg_text |
+----------------+----------+----------+----------+
| test.ft_innodb | optimize | status   | OK       |
+----------------+----------+----------+----------+

SELECT * FROM INNODB_FT_INDEX_TABLE;
+------------+--------------+-------------+-----------+--------+----------+
| WORD       | FIRST_DOC_ID | LAST_DOC_ID | DOC_COUNT | DOC_ID | POSITION |
+------------+--------------+-------------+-----------+--------+----------+
| and        |            4 |           5 |         2 |      4 |        0 |
| and        |            4 |           5 |         2 |      5 |        0 |
| arrived    |            4 |           4 |         1 |      4 |       20 |
| ate        |            1 |           5 |         2 |      1 |        4 |
| ate        |            1 |           5 |         2 |      5 |        8 |
| everybody  |            1 |           1 |         1 |      1 |        8 |
| goldilocks |            4 |           4 |         1 |      4 |        9 |
| hungry     |            3 |           3 |         1 |      3 |        8 |
| pear       |            5 |           5 |         1 |      5 |       14 |
| she        |            5 |           5 |         1 |      5 |        4 |
| then       |            4 |           4 |         1 |      4 |        4 |
| wicked     |            2 |           2 |         1 |      2 |        4 |
| witch      |            2 |           2 |         1 |      2 |       11 |
+------------+--------------+-------------+-----------+--------+----------+

1.1.1.2.9.1.1.1.17 Information Schema INNODB_LOCK_WAITS Table

The Information Schema INNODB_LOCK_WAITS table contains information about blocked InnoDB transactions. The PROCESS privilege is required to view the table.

It contains the following columns:

ColumnDescription
REQUESTING_TRX_IDRequesting transaction ID from the INNODB_TRX table.
REQUESTED_LOCK_IDLock ID from the INNODB.LOCKS table for the waiting transaction.
BLOCKING_TRX_IDBlocking transaction ID from the INNODB_TRX table.
BLOCKING_LOCK_IDLock ID from the INNODB.LOCKS table of a lock held by a transaction that is blocking another transaction.

The table is often used in conjunction with the INNODB_LOCKS and INNODB_TRX tables to diagnose problematic locks and transactions.

1.1.1.2.9.1.1.1.18 Information Schema INNODB_LOCKS Table

The Information Schema INNODB_LOCKS table stores information about locks that InnoDB transactions have requested but not yet acquired, or that are blocking another transaction.

It has the following columns:

ColumnDescription
LOCK_IDLock ID number - the format is not fixed, so do not rely upon the number for information.
LOCK_TRX_IDLock's transaction ID. Matches the INNODB_TRX.TRX_ID column.
LOCK_MODELock mode. One of S (shared), X (exclusive), IS (intention shared), IX (intention exclusive row lock), S_GAP (shared gap lock), X_GAP (exclusive gap lock), IS_GAP (intention shared gap lock), IX_GAP (intention exclusive gap lock) or AUTO_INC (auto-increment table level lock).
LOCK_TYPEWhether the lock is RECORD (row level) or TABLE level.
LOCK_TABLEName of the locked table,or table containing locked rows.
LOCK_INDEXIndex name if a RECORD LOCK_TYPE, or NULL if not.
LOCK_SPACETablespace ID if a RECORD LOCK_TYPE, or NULL if not.
LOCK_PAGELocked record page number if a RECORD LOCK_TYPE, or NULL if not.
LOCK_RECLocked record heap number if a RECORD LOCK_TYPE, or NULL if not.
LOCK_DATALocked record primary key as an SQL string if a RECORD LOCK_TYPE, or NULL if not. If no primary key exists, the internal InnoDB row_id number is instead used. To avoid unnecessary IO, also NULL if the locked record page is not in the buffer pool

The table is often used in conjunction with the INNODB_LOCK_WAITS and INNODB_TRX tables to diagnose problematic locks and transactions

Example

-- session 1
START TRANSACTION;
UPDATE t SET id = 15 WHERE id = 10;

-- session 2
DELETE FROM t WHERE id = 10;

-- session 1
USE information_schema;
SELECT l.*, t.*
    FROM information_schema.INNODB_LOCKS l
    JOIN information_schema.INNODB_TRX t
        ON l.lock_trx_id = t.trx_id
    WHERE trx_state = 'LOCK WAIT' \G
*************************** 1. row ***************************
                   lock_id: 840:40:3:2
               lock_trx_id: 840
                 lock_mode: X
                 lock_type: RECORD
                lock_table: `test`.`t`
                lock_index: PRIMARY
                lock_space: 40
                 lock_page: 3
                  lock_rec: 2
                 lock_data: 10
                    trx_id: 840
                 trx_state: LOCK WAIT
               trx_started: 2019-12-23 18:43:46
     trx_requested_lock_id: 840:40:3:2
          trx_wait_started: 2019-12-23 18:43:46
                trx_weight: 2
       trx_mysql_thread_id: 46
                 trx_query: DELETE FROM t WHERE id = 10
       trx_operation_state: starting index read
         trx_tables_in_use: 1
         trx_tables_locked: 1
          trx_lock_structs: 2
     trx_lock_memory_bytes: 1136
           trx_rows_locked: 1
         trx_rows_modified: 0
   trx_concurrency_tickets: 0
       trx_isolation_level: REPEATABLE READ
         trx_unique_checks: 1
    trx_foreign_key_checks: 1
trx_last_foreign_key_error: NULL
          trx_is_read_only: 0
trx_autocommit_non_locking: 0

.

1.1.1.2.9.1.1.1.19 Information Schema INNODB_METRICS Table

Contents

  1. Enabling and Disabling Counters
  2. Resetting Counters
  3. Simplifying from MariaDB 10.6
  4. Examples

The Information Schema INNODB_METRICS table contains a list of useful InnoDB performance metrics. Each row in the table represents an instrumented counter that can be stopped, started and reset, and which can be grouped together by module.

The PROCESS privilege is required to view the table.

It has the following columns:

ColumnDescription
NAMEUnique counter name.
SUBSYSTEMInnoDB subsystem. See below for the matching module to use to enable/disable monitoring this subsytem with the innodb_monitor_enable and innodb_monitor_disable system variables.
COUNTCount since being enabled.
MAX_COUNTMaximum value since being enabled.
MIN_COUNTMinimum value since being enabled.
AVG_COUNTAverage value since being enabled.
COUNT_RESETCount since last being reset.
MAX_COUNT_RESETMaximum value since last being reset.
MIN_COUNT_RESETMinimum value since last being reset.
AVG_COUNT_RESETAverage value since last being reset.
TIME_ENABLEDTime last enabled.
TIME_DISABLEDTime last disabled
TIME_ELAPSEDTime since enabled
TIME_RESETTime last reset.
STATUSWhether the counter is currently enabled to disabled.
TYPEItem type; one of counter, value, status_counter, set_owner, set_member.
COMMENTCounter description.

Enabling and Disabling Counters

Most of the counters are disabled by default. To enable them, use the innodb_monitor_enable system variable. You can either enable a variable by its name, for example:

SET GLOBAL innodb_monitor_enable = icp_match;

or enable a number of counters grouped by module. The SUBSYSTEM field indicates which counters are grouped together, but the following module names need to be used:

Module NameSubsytem Field
module_metadatametadata
module_locklock
module_bufferbuffer
module_buf_pagebuffer_page_io
module_osos
module_trxtransaction
module_purgepurge
module_compresscompression
module_filefile_system
module_indexindex
module_adaptive_hashadaptive_hash_index From MariaDB 10.6.2, if innodb_adaptive_hash_index is disabled (the default), adaptive_hash_index will not be updated.
module_ibuf_systemchange_buffer
module_srvserver
module_ddlddl
module_dmldml
module_logrecovery
module_icpicp

There are four counters in the icp subsystem:

SELECT NAME, SUBSYSTEM FROM INNODB_METRICS WHERE SUBSYSTEM='icp';
+------------------+-----------+
| NAME             | SUBSYSTEM |
+------------------+-----------+
| icp_attempts     | icp       |
| icp_no_match     | icp       |
| icp_out_of_range | icp       |
| icp_match        | icp       |
+------------------+-----------+

To enable them all, use the associated module name from the table above, module_icp.

SET GLOBAL innodb_monitor_enable = module_icp;

The % wildcard, used to represent any number of characters, can also be used when naming counters, for example:

SET GLOBAL innodb_monitor_enable = 'buffer%'

To disable counters, use the innodb_monitor_disable system variable, using the same naming rules as described above for enabling.

Counter status is not persistent, and will be reset when the server restarts. It is possible to use the options on the command line, or the innodb_monitor_enable option only in a configuration file.

Resetting Counters

Counters can also be reset. Resetting sets all the *_COUNT_RESET values to zero, while leaving the *_COUNT values, which perform counts since the counter was enabled, untouched. Resetting is performed with the innodb_monitor_reset (for individual counters) and innodb_monitor_reset_all (for all counters) system variables.

Simplifying from MariaDB 10.6

MariaDB starting with 10.6

From MariaDB 10.6, the interface was simplified by removing the following:

  • buffer_LRU_batches_flush
  • buffer_LRU_batch_flush_pages
  • buffer_LRU_batches_evict
  • buffer_LRU_batch_evict_pages

and by making the following reflect the status variables:

The intention is to eventually remove the interface entirely (see MDEV-15706).

Examples

Until MariaDB 10.5:

SELECT name,subsystem,type,comment FROM INFORMATION_SCHEMA.INNODB_METRICS;
+--------------------------------------------+---------------------+----------------+------------------------------------------------------------------------------------------------------------------+
| name                                       | subsystem           | type           | comment                                                                                                          |
+--------------------------------------------+---------------------+----------------+------------------------------------------------------------------------------------------------------------------+
| metadata_table_handles_opened              | metadata            | counter        | Number of table handles opened                                                                                   |
| metadata_table_handles_closed              | metadata            | counter        | Number of table handles closed                                                                                   |
| metadata_table_reference_count             | metadata            | counter        | Table reference counter                                                                                          |
| lock_deadlocks                             | lock                | counter        | Number of deadlocks                                                                                              |
| lock_timeouts                              | lock                | counter        | Number of lock timeouts                                                                                          |
| lock_rec_lock_waits                        | lock                | counter        | Number of times enqueued into record lock wait queue                                                             |
| lock_table_lock_waits                      | lock                | counter        | Number of times enqueued into table lock wait queue                                                              |
| lock_rec_lock_requests                     | lock                | counter        | Number of record locks requested                                                                                 |
| lock_rec_lock_created                      | lock                | counter        | Number of record locks created                                                                                   |
| lock_rec_lock_removed                      | lock                | counter        | Number of record locks removed from the lock queue                                                               |
| lock_rec_locks                             | lock                | counter        | Current number of record locks on tables                                                                         |
| lock_table_lock_created                    | lock                | counter        | Number of table locks created                                                                                    |
| lock_table_lock_removed                    | lock                | counter        | Number of table locks removed from the lock queue                                                                |
| lock_table_locks                           | lock                | counter        | Current number of table locks on tables                                                                          |
| lock_row_lock_current_waits                | lock                | status_counter | Number of row locks currently being waited for (innodb_row_lock_current_waits)                                   |
| lock_row_lock_time                         | lock                | status_counter | Time spent in acquiring row locks, in milliseconds (innodb_row_lock_time)                                        |
| lock_row_lock_time_max                     | lock                | value          | The maximum time to acquire a row lock, in milliseconds (innodb_row_lock_time_max)                               |
| lock_row_lock_waits                        | lock                | status_counter | Number of times a row lock had to be waited for (innodb_row_lock_waits)                                          |
| lock_row_lock_time_avg                     | lock                | value          | The average time to acquire a row lock, in milliseconds (innodb_row_lock_time_avg)                               |
| buffer_pool_size                           | server              | value          | Server buffer pool size (all buffer pools) in bytes                                                              |
| buffer_pool_reads                          | buffer              | status_counter | Number of reads directly from disk (innodb_buffer_pool_reads)                                                    |
| buffer_pool_read_requests                  | buffer              | status_counter | Number of logical read requests (innodb_buffer_pool_read_requests)                                               |
| buffer_pool_write_requests                 | buffer              | status_counter | Number of write requests (innodb_buffer_pool_write_requests)                                                     |
| buffer_pool_wait_free                      | buffer              | status_counter | Number of times waited for free buffer (innodb_buffer_pool_wait_free)                                            |
| buffer_pool_read_ahead                     | buffer              | status_counter | Number of pages read as read ahead (innodb_buffer_pool_read_ahead)                                               |
| buffer_pool_read_ahead_evicted             | buffer              | status_counter | Read-ahead pages evicted without being accessed (innodb_buffer_pool_read_ahead_evicted)                          |
| buffer_pool_pages_total                    | buffer              | value          | Total buffer pool size in pages (innodb_buffer_pool_pages_total)                                                 |
| buffer_pool_pages_misc                     | buffer              | value          | Buffer pages for misc use such as row locks or the adaptive hash index (innodb_buffer_pool_pages_misc)           |
| buffer_pool_pages_data                     | buffer              | value          | Buffer pages containing data (innodb_buffer_pool_pages_data)                                                     |
| buffer_pool_bytes_data                     | buffer              | value          | Buffer bytes containing data (innodb_buffer_pool_bytes_data)                                                     |
| buffer_pool_pages_dirty                    | buffer              | value          | Buffer pages currently dirty (innodb_buffer_pool_pages_dirty)                                                    |
| buffer_pool_bytes_dirty                    | buffer              | value          | Buffer bytes currently dirty (innodb_buffer_pool_bytes_dirty)                                                    |
| buffer_pool_pages_free                     | buffer              | value          | Buffer pages currently free (innodb_buffer_pool_pages_free)                                                      |
| buffer_pages_created                       | buffer              | status_counter | Number of pages created (innodb_pages_created)                                                                   |
| buffer_pages_written                       | buffer              | status_counter | Number of pages written (innodb_pages_written)                                                                   |
| buffer_index_pages_written                 | buffer              | status_counter | Number of index pages written (innodb_index_pages_written)                                                       |
| buffer_non_index_pages_written             | buffer              | status_counter | Number of non index pages written (innodb_non_index_pages_written)                                               |
| buffer_pages_read                          | buffer              | status_counter | Number of pages read (innodb_pages_read)                                                                         |
| buffer_index_sec_rec_cluster_reads         | buffer              | status_counter | Number of secondary record reads triggered cluster read                                                          |
| buffer_index_sec_rec_cluster_reads_avoided | buffer              | status_counter | Number of secondary record reads avoided triggering cluster read                                                 |
| buffer_data_reads                          | buffer              | status_counter | Amount of data read in bytes (innodb_data_reads)                                                                 |
| buffer_data_written                        | buffer              | status_counter | Amount of data written in bytes (innodb_data_written)                                                            |
| buffer_flush_batch_scanned                 | buffer              | set_owner      | Total pages scanned as part of flush batch                                                                       |
| buffer_flush_batch_num_scan                | buffer              | set_member     | Number of times buffer flush list flush is called                                                                |
| buffer_flush_batch_scanned_per_call        | buffer              | set_member     | Pages scanned per flush batch scan                                                                               |
| buffer_flush_batch_total_pages             | buffer              | set_owner      | Total pages flushed as part of flush batch                                                                       |
| buffer_flush_batches                       | buffer              | set_member     | Number of flush batches                                                                                          |
| buffer_flush_batch_pages                   | buffer              | set_member     | Pages queued as a flush batch                                                                                    |
| buffer_flush_neighbor_total_pages          | buffer              | set_owner      | Total neighbors flushed as part of neighbor flush                                                                |
| buffer_flush_neighbor                      | buffer              | set_member     | Number of times neighbors flushing is invoked                                                                    |
| buffer_flush_neighbor_pages                | buffer              | set_member     | Pages queued as a neighbor batch                                                                                 |
| buffer_flush_n_to_flush_requested          | buffer              | counter        | Number of pages requested for flushing.                                                                          |
| buffer_flush_n_to_flush_by_age             | buffer              | counter        | Number of pages target by LSN Age for flushing.                                                                  |
| buffer_flush_adaptive_avg_time             | buffer              | counter        | Avg time (ms) spent for adaptive flushing recently.                                                              |
| buffer_flush_adaptive_avg_pass             | buffer              | counter        | Number of adaptive flushes passed during the recent Avg period.                                                  |
| buffer_LRU_get_free_loops                  | buffer              | counter        | Total loops in LRU get free.                                                                                     |
| buffer_LRU_get_free_waits                  | buffer              | counter        | Total sleep waits in LRU get free.                                                                               |
| buffer_flush_avg_page_rate                 | buffer              | counter        | Average number of pages at which flushing is happening                                                           |
| buffer_flush_lsn_avg_rate                  | buffer              | counter        | Average redo generation rate                                                                                     |
| buffer_flush_pct_for_dirty                 | buffer              | counter        | Percent of IO capacity used to avoid max dirty page limit                                                        |
| buffer_flush_pct_for_lsn                   | buffer              | counter        | Percent of IO capacity used to avoid reusable redo space limit                                                   |
| buffer_flush_sync_waits                    | buffer              | counter        | Number of times a wait happens due to sync flushing                                                              |
| buffer_flush_adaptive_total_pages          | buffer              | set_owner      | Total pages flushed as part of adaptive flushing                                                                 |
| buffer_flush_adaptive                      | buffer              | set_member     | Number of adaptive batches                                                                                       |
| buffer_flush_adaptive_pages                | buffer              | set_member     | Pages queued as an adaptive batch                                                                                |
| buffer_flush_sync_total_pages              | buffer              | set_owner      | Total pages flushed as part of sync batches                                                                      |
| buffer_flush_sync                          | buffer              | set_member     | Number of sync batches                                                                                           |
| buffer_flush_sync_pages                    | buffer              | set_member     | Pages queued as a sync batch                                                                                     |
| buffer_flush_background_total_pages        | buffer              | set_owner      | Total pages flushed as part of background batches                                                                |
| buffer_flush_background                    | buffer              | set_member     | Number of background batches                                                                                     |
| buffer_flush_background_pages              | buffer              | set_member     | Pages queued as a background batch                                                                               |
| buffer_LRU_batch_scanned                   | buffer              | set_owner      | Total pages scanned as part of LRU batch                                                                         |
| buffer_LRU_batch_num_scan                  | buffer              | set_member     | Number of times LRU batch is called                                                                              |
| buffer_LRU_batch_scanned_per_call          | buffer              | set_member     | Pages scanned per LRU batch call                                                                                 |
| buffer_LRU_batch_flush_total_pages         | buffer              | set_owner      | Total pages flushed as part of LRU batches                                                                       |
| buffer_LRU_batches_flush                   | buffer              | set_member     | Number of LRU batches                                                                                            |
| buffer_LRU_batch_flush_pages               | buffer              | set_member     | Pages queued as an LRU batch                                                                                     |
| buffer_LRU_batch_evict_total_pages         | buffer              | set_owner      | Total pages evicted as part of LRU batches                                                                       |
| buffer_LRU_batches_evict                   | buffer              | set_member     | Number of LRU batches                                                                                            |
| buffer_LRU_batch_evict_pages               | buffer              | set_member     | Pages queued as an LRU batch                                                                                     |
| buffer_LRU_single_flush_failure_count      | Buffer              | counter        | Number of times attempt to flush a single page from LRU failed                                                   |
| buffer_LRU_get_free_search                 | Buffer              | counter        | Number of searches performed for a clean page                                                                    |
| buffer_LRU_search_scanned                  | buffer              | set_owner      | Total pages scanned as part of LRU search                                                                        |
| buffer_LRU_search_num_scan                 | buffer              | set_member     | Number of times LRU search is performed                                                                          |
| buffer_LRU_search_scanned_per_call         | buffer              | set_member     | Page scanned per single LRU search                                                                               |
| buffer_LRU_unzip_search_scanned            | buffer              | set_owner      | Total pages scanned as part of LRU unzip search                                                                  |
| buffer_LRU_unzip_search_num_scan           | buffer              | set_member     | Number of times LRU unzip search is performed                                                                    |
| buffer_LRU_unzip_search_scanned_per_call   | buffer              | set_member     | Page scanned per single LRU unzip search                                                                         |
| buffer_page_read_index_leaf                | buffer_page_io      | counter        | Number of Index Leaf Pages read                                                                                  |
| buffer_page_read_index_non_leaf            | buffer_page_io      | counter        | Number of Index Non-leaf Pages read                                                                              |
| buffer_page_read_index_ibuf_leaf           | buffer_page_io      | counter        | Number of Insert Buffer Index Leaf Pages read                                                                    |
| buffer_page_read_index_ibuf_non_leaf       | buffer_page_io      | counter        | Number of Insert Buffer Index Non-Leaf Pages read                                                                |
| buffer_page_read_undo_log                  | buffer_page_io      | counter        | Number of Undo Log Pages read                                                                                    |
| buffer_page_read_index_inode               | buffer_page_io      | counter        | Number of Index Inode Pages read                                                                                 |
| buffer_page_read_ibuf_free_list            | buffer_page_io      | counter        | Number of Insert Buffer Free List Pages read                                                                     |
| buffer_page_read_ibuf_bitmap               | buffer_page_io      | counter        | Number of Insert Buffer Bitmap Pages read                                                                        |
| buffer_page_read_system_page               | buffer_page_io      | counter        | Number of System Pages read                                                                                      |
| buffer_page_read_trx_system                | buffer_page_io      | counter        | Number of Transaction System Pages read                                                                          |
| buffer_page_read_fsp_hdr                   | buffer_page_io      | counter        | Number of File Space Header Pages read                                                                           |
| buffer_page_read_xdes                      | buffer_page_io      | counter        | Number of Extent Descriptor Pages read                                                                           |
| buffer_page_read_blob                      | buffer_page_io      | counter        | Number of Uncompressed BLOB Pages read                                                                           |
| buffer_page_read_zblob                     | buffer_page_io      | counter        | Number of First Compressed BLOB Pages read                                                                       |
| buffer_page_read_zblob2                    | buffer_page_io      | counter        | Number of Subsequent Compressed BLOB Pages read                                                                  |
| buffer_page_read_other                     | buffer_page_io      | counter        | Number of other/unknown (old version of InnoDB) Pages read                                                       |
| buffer_page_written_index_leaf             | buffer_page_io      | counter        | Number of Index Leaf Pages written                                                                               |
| buffer_page_written_index_non_leaf         | buffer_page_io      | counter        | Number of Index Non-leaf Pages written                                                                           |
| buffer_page_written_index_ibuf_leaf        | buffer_page_io      | counter        | Number of Insert Buffer Index Leaf Pages written                                                                 |
| buffer_page_written_index_ibuf_non_leaf    | buffer_page_io      | counter        | Number of Insert Buffer Index Non-Leaf Pages written                                                             |
| buffer_page_written_undo_log               | buffer_page_io      | counter        | Number of Undo Log Pages written                                                                                 |
| buffer_page_written_index_inode            | buffer_page_io      | counter        | Number of Index Inode Pages written                                                                              |
| buffer_page_written_ibuf_free_list         | buffer_page_io      | counter        | Number of Insert Buffer Free List Pages written                                                                  |
| buffer_page_written_ibuf_bitmap            | buffer_page_io      | counter        | Number of Insert Buffer Bitmap Pages written                                                                     |
| buffer_page_written_system_page            | buffer_page_io      | counter        | Number of System Pages written                                                                                   |
| buffer_page_written_trx_system             | buffer_page_io      | counter        | Number of Transaction System Pages written                                                                       |
| buffer_page_written_fsp_hdr                | buffer_page_io      | counter        | Number of File Space Header Pages written                                                                        |
| buffer_page_written_xdes                   | buffer_page_io      | counter        | Number of Extent Descriptor Pages written                                                                        |
| buffer_page_written_blob                   | buffer_page_io      | counter        | Number of Uncompressed BLOB Pages written                                                                        |
| buffer_page_written_zblob                  | buffer_page_io      | counter        | Number of First Compressed BLOB Pages written                                                                    |
| buffer_page_written_zblob2                 | buffer_page_io      | counter        | Number of Subsequent Compressed BLOB Pages written                                                               |
| buffer_page_written_other                  | buffer_page_io      | counter        | Number of other/unknown (old version InnoDB) Pages written                                                       |
| os_data_reads                              | os                  | status_counter | Number of reads initiated (innodb_data_reads)                                                                    |
| os_data_writes                             | os                  | status_counter | Number of writes initiated (innodb_data_writes)                                                                  |
| os_data_fsyncs                             | os                  | status_counter | Number of fsync() calls (innodb_data_fsyncs)                                                                     |
| os_pending_reads                           | os                  | counter        | Number of reads pending                                                                                          |
| os_pending_writes                          | os                  | counter        | Number of writes pending                                                                                         |
| os_log_bytes_written                       | os                  | status_counter | Bytes of log written (innodb_os_log_written)                                                                     |
| os_log_fsyncs                              | os                  | status_counter | Number of fsync log writes (innodb_os_log_fsyncs)                                                                |
| os_log_pending_fsyncs                      | os                  | status_counter | Number of pending fsync write (innodb_os_log_pending_fsyncs)                                                     |
| os_log_pending_writes                      | os                  | status_counter | Number of pending log file writes (innodb_os_log_pending_writes)                                                 |
| trx_rw_commits                             | transaction         | counter        | Number of read-write transactions  committed                                                                     |
| trx_ro_commits                             | transaction         | counter        | Number of read-only transactions committed                                                                       |
| trx_nl_ro_commits                          | transaction         | counter        | Number of non-locking auto-commit read-only transactions committed                                               |
| trx_commits_insert_update                  | transaction         | counter        | Number of transactions committed with inserts and updates                                                        |
| trx_rollbacks                              | transaction         | counter        | Number of transactions rolled back                                                                               |
| trx_rollbacks_savepoint                    | transaction         | counter        | Number of transactions rolled back to savepoint                                                                  |
| trx_active_transactions                    | transaction         | counter        | Number of active transactions                                                                                    |
| trx_rseg_history_len                       | transaction         | value          | Length of the TRX_RSEG_HISTORY list                                                                              |
| trx_undo_slots_used                        | transaction         | counter        | Number of undo slots used                                                                                        |
| trx_undo_slots_cached                      | transaction         | counter        | Number of undo slots cached                                                                                      |
| trx_rseg_current_size                      | transaction         | value          | Current rollback segment size in pages                                                                           |
| purge_del_mark_records                     | purge               | counter        | Number of delete-marked rows purged                                                                              |
| purge_upd_exist_or_extern_records          | purge               | counter        | Number of purges on updates of existing records and updates on delete marked record with externally stored field |
| purge_invoked                              | purge               | counter        | Number of times purge was invoked                                                                                |
| purge_undo_log_pages                       | purge               | counter        | Number of undo log pages handled by the purge                                                                    |
| purge_dml_delay_usec                       | purge               | value          | Microseconds DML to be delayed due to purge lagging                                                              |
| purge_stop_count                           | purge               | value          | Number of times purge was stopped                                                                                |
| purge_resume_count                         | purge               | value          | Number of times purge was resumed                                                                                |
| log_checkpoints                            | recovery            | counter        | Number of checkpoints                                                                                            |
| log_lsn_last_flush                         | recovery            | value          | LSN of Last flush                                                                                                |
| log_lsn_last_checkpoint                    | recovery            | value          | LSN at last checkpoint                                                                                           |
| log_lsn_current                            | recovery            | value          | Current LSN value                                                                                                |
| log_lsn_checkpoint_age                     | recovery            | value          | Current LSN value minus LSN at last checkpoint                                                                   |
| log_lsn_buf_pool_oldest                    | recovery            | value          | The oldest modified block LSN in the buffer pool                                                                 |
| log_max_modified_age_async                 | recovery            | value          | Maximum LSN difference; when exceeded, start asynchronous preflush                                               |
| log_pending_log_flushes                    | recovery            | value          | Pending log flushes                                                                                              |
| log_pending_checkpoint_writes              | recovery            | value          | Pending checkpoints                                                                                              |
| log_num_log_io                             | recovery            | value          | Number of log I/Os                                                                                               |
| log_waits                                  | recovery            | status_counter | Number of log waits due to small log buffer (innodb_log_waits)                                                   |
| log_write_requests                         | recovery            | status_counter | Number of log write requests (innodb_log_write_requests)                                                         |
| log_writes                                 | recovery            | status_counter | Number of log writes (innodb_log_writes)                                                                         |
| log_padded                                 | recovery            | status_counter | Bytes of log padded for log write ahead                                                                          |
| compress_pages_compressed                  | compression         | counter        | Number of pages compressed                                                                                       |
| compress_pages_decompressed                | compression         | counter        | Number of pages decompressed                                                                                     |
| compression_pad_increments                 | compression         | counter        | Number of times padding is incremented to avoid compression failures                                             |
| compression_pad_decrements                 | compression         | counter        | Number of times padding is decremented due to good compressibility                                               |
| compress_saved                             | compression         | counter        | Number of bytes saved by page compression                                                                        |
| compress_pages_page_compressed             | compression         | counter        | Number of pages compressed by page compression                                                                   |
| compress_page_compressed_trim_op           | compression         | counter        | Number of TRIM operation performed by page compression                                                           |
| compress_pages_page_decompressed           | compression         | counter        | Number of pages decompressed by page compression                                                                 |
| compress_pages_page_compression_error      | compression         | counter        | Number of page compression errors                                                                                |
| compress_pages_encrypted                   | compression         | counter        | Number of pages encrypted                                                                                        |
| compress_pages_decrypted                   | compression         | counter        | Number of pages decrypted                                                                                        |
| index_page_splits                          | index               | counter        | Number of index page splits                                                                                      |
| index_page_merge_attempts                  | index               | counter        | Number of index page merge attempts                                                                              |
| index_page_merge_successful                | index               | counter        | Number of successful index page merges                                                                           |
| index_page_reorg_attempts                  | index               | counter        | Number of index page reorganization attempts                                                                     |
| index_page_reorg_successful                | index               | counter        | Number of successful index page reorganizations                                                                  |
| index_page_discards                        | index               | counter        | Number of index pages discarded                                                                                  |
| adaptive_hash_searches                     | adaptive_hash_index | status_counter | Number of successful searches using Adaptive Hash Index                                                          |
| adaptive_hash_searches_btree               | adaptive_hash_index | status_counter | Number of searches using B-tree on an index search                                                               |
| adaptive_hash_pages_added                  | adaptive_hash_index | counter        | Number of index pages on which the Adaptive Hash Index is built                                                  |
| adaptive_hash_pages_removed                | adaptive_hash_index | counter        | Number of index pages whose corresponding Adaptive Hash Index entries were removed                               |
| adaptive_hash_rows_added                   | adaptive_hash_index | counter        | Number of Adaptive Hash Index rows added                                                                         |
| adaptive_hash_rows_removed                 | adaptive_hash_index | counter        | Number of Adaptive Hash Index rows removed                                                                       |
| adaptive_hash_rows_deleted_no_hash_entry   | adaptive_hash_index | counter        | Number of rows deleted that did not have corresponding Adaptive Hash Index entries                               |
| adaptive_hash_rows_updated                 | adaptive_hash_index | counter        | Number of Adaptive Hash Index rows updated                                                                       |
| file_num_open_files                        | file_system         | value          | Number of files currently open (innodb_num_open_files)                                                           |
| ibuf_merges_insert                         | change_buffer       | status_counter | Number of inserted records merged by change buffering                                                            |
| ibuf_merges_delete_mark                    | change_buffer       | status_counter | Number of deleted records merged by change buffering                                                             |
| ibuf_merges_delete                         | change_buffer       | status_counter | Number of purge records merged by change buffering                                                               |
| ibuf_merges_discard_insert                 | change_buffer       | status_counter | Number of insert merged operations discarded                                                                     |
| ibuf_merges_discard_delete_mark            | change_buffer       | status_counter | Number of deleted merged operations discarded                                                                    |
| ibuf_merges_discard_delete                 | change_buffer       | status_counter | Number of purge merged  operations discarded                                                                     |
| ibuf_merges                                | change_buffer       | status_counter | Number of change buffer merges                                                                                   |
| ibuf_size                                  | change_buffer       | status_counter | Change buffer size in pages                                                                                      |
| innodb_master_thread_sleeps                | server              | counter        | Number of times (seconds) master thread sleeps                                                                   |
| innodb_activity_count                      | server              | status_counter | Current server activity count                                                                                    |
| innodb_master_active_loops                 | server              | counter        | Number of times master thread performs its tasks when server is active                                           |
| innodb_master_idle_loops                   | server              | counter        | Number of times master thread performs its tasks when server is idle                                             |
| innodb_background_drop_table_usec          | server              | counter        | Time (in microseconds) spent to process drop table list                                                          |
| innodb_log_flush_usec                      | server              | counter        | Time (in microseconds) spent to flush log records                                                                |
| innodb_dict_lru_usec                       | server              | counter        | Time (in microseconds) spent to process DICT LRU list                                                            |
| innodb_dict_lru_count_active               | server              | counter        | Number of tables evicted from DICT LRU list in the active loop                                                   |
| innodb_dict_lru_count_idle                 | server              | counter        | Number of tables evicted from DICT LRU list in the idle loop                                                     |
| innodb_dblwr_writes                        | server              | status_counter | Number of doublewrite operations that have been performed (innodb_dblwr_writes)                                  |
| innodb_dblwr_pages_written                 | server              | status_counter | Number of pages that have been written for doublewrite operations (innodb_dblwr_pages_written)                   |
| innodb_page_size                           | server              | value          | InnoDB page size in bytes (innodb_page_size)                                                                     |
| innodb_rwlock_s_spin_waits                 | server              | status_counter | Number of rwlock spin waits due to shared latch request                                                          |
| innodb_rwlock_x_spin_waits                 | server              | status_counter | Number of rwlock spin waits due to exclusive latch request                                                       |
| innodb_rwlock_sx_spin_waits                | server              | status_counter | Number of rwlock spin waits due to sx latch request                                                              |
| innodb_rwlock_s_spin_rounds                | server              | status_counter | Number of rwlock spin loop rounds due to shared latch request                                                    |
| innodb_rwlock_x_spin_rounds                | server              | status_counter | Number of rwlock spin loop rounds due to exclusive latch request                                                 |
| innodb_rwlock_sx_spin_rounds               | server              | status_counter | Number of rwlock spin loop rounds due to sx latch request                                                        |
| innodb_rwlock_s_os_waits                   | server              | status_counter | Number of OS waits due to shared latch request                                                                   |
| innodb_rwlock_x_os_waits                   | server              | status_counter | Number of OS waits due to exclusive latch request                                                                |
| innodb_rwlock_sx_os_waits                  | server              | status_counter | Number of OS waits due to sx latch request                                                                       |
| dml_reads                                  | dml                 | status_counter | Number of rows read                                                                                              |
| dml_inserts                                | dml                 | status_counter | Number of rows inserted                                                                                          |
| dml_deletes                                | dml                 | status_counter | Number of rows deleted                                                                                           |
| dml_updates                                | dml                 | status_counter | Number of rows updated                                                                                           |
| dml_system_reads                           | dml                 | status_counter | Number of system rows read                                                                                       |
| dml_system_inserts                         | dml                 | status_counter | Number of system rows inserted                                                                                   |
| dml_system_deletes                         | dml                 | status_counter | Number of system rows deleted                                                                                    |
| dml_system_updates                         | dml                 | status_counter | Number of system rows updated                                                                                    |
| ddl_background_drop_indexes                | ddl                 | counter        | Number of indexes waiting to be dropped after failed index creation                                              |
| ddl_background_drop_tables                 | ddl                 | counter        | Number of tables in background drop table list                                                                   |
| ddl_online_create_index                    | ddl                 | counter        | Number of indexes being created online                                                                           |
| ddl_pending_alter_table                    | ddl                 | counter        | Number of ALTER TABLE, CREATE INDEX, DROP INDEX in progress                                                      |
| ddl_sort_file_alter_table                  | ddl                 | counter        | Number of sort files created during alter table                                                                  |
| ddl_log_file_alter_table                   | ddl                 | counter        | Number of log files created during alter table                                                                   |
| icp_attempts                               | icp                 | counter        | Number of attempts for index push-down condition checks                                                          |
| icp_no_match                               | icp                 | counter        | Index push-down condition does not match                                                                         |
| icp_out_of_range                           | icp                 | counter        | Index push-down condition out of range                                                                           |
| icp_match                                  | icp                 | counter        | Index push-down condition matches                                                                                |
+--------------------------------------------+---------------------+----------------+------------------------------------------------------------------------------------------------------------------+
234 rows in set (0.001 sec)

From MariaDB 10.6

SELECT name,subsystem,type,comment FROM INFORMATION_SCHEMA.INNODB_METRICS;
+--------------------------------------------+---------------------+----------------+------------------------------------------------------------------------------------------------------------------+
| name                                       | subsystem           | type           | comment                                                                                                          |
+--------------------------------------------+---------------------+----------------+------------------------------------------------------------------------------------------------------------------+
| metadata_table_handles_opened              | metadata            | counter        | Number of table handles opened                                                                                   |
| lock_deadlocks                             | lock                | value          | Number of deadlocks                                                                                              |
| lock_timeouts                              | lock                | value          | Number of lock timeouts                                                                                          |
| lock_rec_lock_waits                        | lock                | counter        | Number of times enqueued into record lock wait queue                                                             |
| lock_table_lock_waits                      | lock                | counter        | Number of times enqueued into table lock wait queue                                                              |
| lock_rec_lock_requests                     | lock                | counter        | Number of record locks requested                                                                                 |
| lock_rec_lock_created                      | lock                | counter        | Number of record locks created                                                                                   |
| lock_rec_lock_removed                      | lock                | counter        | Number of record locks removed from the lock queue                                                               |
| lock_rec_locks                             | lock                | counter        | Current number of record locks on tables                                                                         |
| lock_table_lock_created                    | lock                | counter        | Number of table locks created                                                                                    |
| lock_table_lock_removed                    | lock                | counter        | Number of table locks removed from the lock queue                                                                |
| lock_table_locks                           | lock                | counter        | Current number of table locks on tables                                                                          |
| lock_row_lock_current_waits                | lock                | status_counter | Number of row locks currently being waited for (innodb_row_lock_current_waits)                                   |
| lock_row_lock_time                         | lock                | status_counter | Time spent in acquiring row locks, in milliseconds (innodb_row_lock_time)                                        |
| lock_row_lock_time_max                     | lock                | value          | The maximum time to acquire a row lock, in milliseconds (innodb_row_lock_time_max)                               |
| lock_row_lock_waits                        | lock                | status_counter | Number of times a row lock had to be waited for (innodb_row_lock_waits)                                          |
| lock_row_lock_time_avg                     | lock                | value          | The average time to acquire a row lock, in milliseconds (innodb_row_lock_time_avg)                               |
| buffer_pool_size                           | server              | value          | Server buffer pool size (all buffer pools) in bytes                                                              |
| buffer_pool_reads                          | buffer              | status_counter | Number of reads directly from disk (innodb_buffer_pool_reads)                                                    |
| buffer_pool_read_requests                  | buffer              | status_counter | Number of logical read requests (innodb_buffer_pool_read_requests)                                               |
| buffer_pool_write_requests                 | buffer              | status_counter | Number of write requests (innodb_buffer_pool_write_requests)                                                     |
| buffer_pool_wait_free                      | buffer              | status_counter | Number of times waited for free buffer (innodb_buffer_pool_wait_free)                                            |
| buffer_pool_read_ahead                     | buffer              | status_counter | Number of pages read as read ahead (innodb_buffer_pool_read_ahead)                                               |
| buffer_pool_read_ahead_evicted             | buffer              | status_counter | Read-ahead pages evicted without being accessed (innodb_buffer_pool_read_ahead_evicted)                          |
| buffer_pool_pages_total                    | buffer              | value          | Total buffer pool size in pages (innodb_buffer_pool_pages_total)                                                 |
| buffer_pool_pages_misc                     | buffer              | value          | Buffer pages for misc use such as row locks or the adaptive hash index (innodb_buffer_pool_pages_misc)           |
| buffer_pool_pages_data                     | buffer              | value          | Buffer pages containing data (innodb_buffer_pool_pages_data)                                                     |
| buffer_pool_bytes_data                     | buffer              | value          | Buffer bytes containing data (innodb_buffer_pool_bytes_data)                                                     |
| buffer_pool_pages_dirty                    | buffer              | value          | Buffer pages currently dirty (innodb_buffer_pool_pages_dirty)                                                    |
| buffer_pool_bytes_dirty                    | buffer              | value          | Buffer bytes currently dirty (innodb_buffer_pool_bytes_dirty)                                                    |
| buffer_pool_pages_free                     | buffer              | value          | Buffer pages currently free (innodb_buffer_pool_pages_free)                                                      |
| buffer_pages_created                       | buffer              | status_counter | Number of pages created (innodb_pages_created)                                                                   |
| buffer_pages_written                       | buffer              | status_counter | Number of pages written (innodb_pages_written)                                                                   |
| buffer_index_pages_written                 | buffer              | status_counter | Number of index pages written (innodb_index_pages_written)                                                       |
| buffer_non_index_pages_written             | buffer              | status_counter | Number of non index pages written (innodb_non_index_pages_written)                                               |
| buffer_pages_read                          | buffer              | status_counter | Number of pages read (innodb_pages_read)                                                                         |
| buffer_index_sec_rec_cluster_reads         | buffer              | status_counter | Number of secondary record reads triggered cluster read                                                          |
| buffer_index_sec_rec_cluster_reads_avoided | buffer              | status_counter | Number of secondary record reads avoided triggering cluster read                                                 |
| buffer_data_reads                          | buffer              | status_counter | Amount of data read in bytes (innodb_data_reads)                                                                 |
| buffer_data_written                        | buffer              | status_counter | Amount of data written in bytes (innodb_data_written)                                                            |
| buffer_flush_batch_scanned                 | buffer              | set_owner      | Total pages scanned as part of flush batch                                                                       |
| buffer_flush_batch_num_scan                | buffer              | set_member     | Number of times buffer flush list flush is called                                                                |
| buffer_flush_batch_scanned_per_call        | buffer              | set_member     | Pages scanned per flush batch scan                                                                               |
| buffer_flush_batch_total_pages             | buffer              | set_owner      | Total pages flushed as part of flush batch                                                                       |
| buffer_flush_batches                       | buffer              | set_member     | Number of flush batches                                                                                          |
| buffer_flush_batch_pages                   | buffer              | set_member     | Pages queued as a flush batch                                                                                    |
| buffer_flush_neighbor_total_pages          | buffer              | set_owner      | Total neighbors flushed as part of neighbor flush                                                                |
| buffer_flush_neighbor                      | buffer              | set_member     | Number of times neighbors flushing is invoked                                                                    |
| buffer_flush_neighbor_pages                | buffer              | set_member     | Pages queued as a neighbor batch                                                                                 |
| buffer_flush_n_to_flush_requested          | buffer              | counter        | Number of pages requested for flushing.                                                                          |
| buffer_flush_n_to_flush_by_age             | buffer              | counter        | Number of pages target by LSN Age for flushing.                                                                  |
| buffer_flush_adaptive_avg_time             | buffer              | counter        | Avg time (ms) spent for adaptive flushing recently.                                                              |
| buffer_flush_adaptive_avg_pass             | buffer              | counter        | Number of adaptive flushes passed during the recent Avg period.                                                  |
| buffer_LRU_get_free_loops                  | buffer              | counter        | Total loops in LRU get free.                                                                                     |
| buffer_LRU_get_free_waits                  | buffer              | counter        | Total sleep waits in LRU get free.                                                                               |
| buffer_flush_avg_page_rate                 | buffer              | counter        | Average number of pages at which flushing is happening                                                           |
| buffer_flush_lsn_avg_rate                  | buffer              | counter        | Average redo generation rate                                                                                     |
| buffer_flush_pct_for_dirty                 | buffer              | counter        | Percent of IO capacity used to avoid max dirty page limit                                                        |
| buffer_flush_pct_for_lsn                   | buffer              | counter        | Percent of IO capacity used to avoid reusable redo space limit                                                   |
| buffer_flush_sync_waits                    | buffer              | counter        | Number of times a wait happens due to sync flushing                                                              |
| buffer_flush_adaptive_total_pages          | buffer              | set_owner      | Total pages flushed as part of adaptive flushing                                                                 |
| buffer_flush_adaptive                      | buffer              | set_member     | Number of adaptive batches                                                                                       |
| buffer_flush_adaptive_pages                | buffer              | set_member     | Pages queued as an adaptive batch                                                                                |
| buffer_flush_sync_total_pages              | buffer              | set_owner      | Total pages flushed as part of sync batches                                                                      |
| buffer_flush_sync                          | buffer              | set_member     | Number of sync batches                                                                                           |
| buffer_flush_sync_pages                    | buffer              | set_member     | Pages queued as a sync batch                                                                                     |
| buffer_flush_background_total_pages        | buffer              | set_owner      | Total pages flushed as part of background batches                                                                |
| buffer_flush_background                    | buffer              | set_member     | Number of background batches                                                                                     |
| buffer_flush_background_pages              | buffer              | set_member     | Pages queued as a background batch                                                                               |
| buffer_LRU_batch_scanned                   | buffer              | set_owner      | Total pages scanned as part of LRU batch                                                                         |
| buffer_LRU_batch_num_scan                  | buffer              | set_member     | Number of times LRU batch is called                                                                              |
| buffer_LRU_batch_scanned_per_call          | buffer              | set_member     | Pages scanned per LRU batch call                                                                                 |
| buffer_LRU_batch_flush_total_pages         | buffer              | status_counter | Total pages flushed as part of LRU batches                                                                       |
| buffer_LRU_batch_evict_total_pages         | buffer              | status_counter | Total pages evicted as part of LRU batches                                                                       |
| buffer_LRU_single_flush_failure_count      | Buffer              | counter        | Number of times attempt to flush a single page from LRU failed                                                   |
| buffer_LRU_get_free_search                 | Buffer              | counter        | Number of searches performed for a clean page                                                                    |
| buffer_LRU_search_scanned                  | buffer              | set_owner      | Total pages scanned as part of LRU search                                                                        |
| buffer_LRU_search_num_scan                 | buffer              | set_member     | Number of times LRU search is performed                                                                          |
| buffer_LRU_search_scanned_per_call         | buffer              | set_member     | Page scanned per single LRU search                                                                               |
| buffer_LRU_unzip_search_scanned            | buffer              | set_owner      | Total pages scanned as part of LRU unzip search                                                                  |
| buffer_LRU_unzip_search_num_scan           | buffer              | set_member     | Number of times LRU unzip search is performed                                                                    |
| buffer_LRU_unzip_search_scanned_per_call   | buffer              | set_member     | Page scanned per single LRU unzip search                                                                         |
| buffer_page_read_index_leaf                | buffer_page_io      | counter        | Number of Index Leaf Pages read                                                                                  |
| buffer_page_read_index_non_leaf            | buffer_page_io      | counter        | Number of Index Non-leaf Pages read                                                                              |
| buffer_page_read_index_ibuf_leaf           | buffer_page_io      | counter        | Number of Insert Buffer Index Leaf Pages read                                                                    |
| buffer_page_read_index_ibuf_non_leaf       | buffer_page_io      | counter        | Number of Insert Buffer Index Non-Leaf Pages read                                                                |
| buffer_page_read_undo_log                  | buffer_page_io      | counter        | Number of Undo Log Pages read                                                                                    |
| buffer_page_read_index_inode               | buffer_page_io      | counter        | Number of Index Inode Pages read                                                                                 |
| buffer_page_read_ibuf_free_list            | buffer_page_io      | counter        | Number of Insert Buffer Free List Pages read                                                                     |
| buffer_page_read_ibuf_bitmap               | buffer_page_io      | counter        | Number of Insert Buffer Bitmap Pages read                                                                        |
| buffer_page_read_system_page               | buffer_page_io      | counter        | Number of System Pages read                                                                                      |
| buffer_page_read_trx_system                | buffer_page_io      | counter        | Number of Transaction System Pages read                                                                          |
| buffer_page_read_fsp_hdr                   | buffer_page_io      | counter        | Number of File Space Header Pages read                                                                           |
| buffer_page_read_xdes                      | buffer_page_io      | counter        | Number of Extent Descriptor Pages read                                                                           |
| buffer_page_read_blob                      | buffer_page_io      | counter        | Number of Uncompressed BLOB Pages read                                                                           |
| buffer_page_read_zblob                     | buffer_page_io      | counter        | Number of First Compressed BLOB Pages read                                                                       |
| buffer_page_read_zblob2                    | buffer_page_io      | counter        | Number of Subsequent Compressed BLOB Pages read                                                                  |
| buffer_page_read_other                     | buffer_page_io      | counter        | Number of other/unknown (old version of InnoDB) Pages read                                                       |
| buffer_page_written_index_leaf             | buffer_page_io      | counter        | Number of Index Leaf Pages written                                                                               |
| buffer_page_written_index_non_leaf         | buffer_page_io      | counter        | Number of Index Non-leaf Pages written                                                                           |
| buffer_page_written_index_ibuf_leaf        | buffer_page_io      | counter        | Number of Insert Buffer Index Leaf Pages written                                                                 |
| buffer_page_written_index_ibuf_non_leaf    | buffer_page_io      | counter        | Number of Insert Buffer Index Non-Leaf Pages written                                                             |
| buffer_page_written_undo_log               | buffer_page_io      | counter        | Number of Undo Log Pages written                                                                                 |
| buffer_page_written_index_inode            | buffer_page_io      | counter        | Number of Index Inode Pages written                                                                              |
| buffer_page_written_ibuf_free_list         | buffer_page_io      | counter        | Number of Insert Buffer Free List Pages written                                                                  |
| buffer_page_written_ibuf_bitmap            | buffer_page_io      | counter        | Number of Insert Buffer Bitmap Pages written                                                                     |
| buffer_page_written_system_page            | buffer_page_io      | counter        | Number of System Pages written                                                                                   |
| buffer_page_written_trx_system             | buffer_page_io      | counter        | Number of Transaction System Pages written                                                                       |
| buffer_page_written_fsp_hdr                | buffer_page_io      | counter        | Number of File Space Header Pages written                                                                        |
| buffer_page_written_xdes                   | buffer_page_io      | counter        | Number of Extent Descriptor Pages written                                                                        |
| buffer_page_written_blob                   | buffer_page_io      | counter        | Number of Uncompressed BLOB Pages written                                                                        |
| buffer_page_written_zblob                  | buffer_page_io      | counter        | Number of First Compressed BLOB Pages written                                                                    |
| buffer_page_written_zblob2                 | buffer_page_io      | counter        | Number of Subsequent Compressed BLOB Pages written                                                               |
| buffer_page_written_other                  | buffer_page_io      | counter        | Number of other/unknown (old version InnoDB) Pages written                                                       |
| os_data_reads                              | os                  | status_counter | Number of reads initiated (innodb_data_reads)                                                                    |
| os_data_writes                             | os                  | status_counter | Number of writes initiated (innodb_data_writes)                                                                  |
| os_data_fsyncs                             | os                  | status_counter | Number of fsync() calls (innodb_data_fsyncs)                                                                     |
| os_pending_reads                           | os                  | counter        | Number of reads pending                                                                                          |
| os_pending_writes                          | os                  | counter        | Number of writes pending                                                                                         |
| os_log_bytes_written                       | os                  | status_counter | Bytes of log written (innodb_os_log_written)                                                                     |
| os_log_fsyncs                              | os                  | status_counter | Number of fsync log writes (innodb_os_log_fsyncs)                                                                |
| os_log_pending_fsyncs                      | os                  | status_counter | Number of pending fsync write (innodb_os_log_pending_fsyncs)                                                     |
| os_log_pending_writes                      | os                  | status_counter | Number of pending log file writes (innodb_os_log_pending_writes)                                                 |
| trx_rw_commits                             | transaction         | counter        | Number of read-write transactions  committed                                                                     |
| trx_ro_commits                             | transaction         | counter        | Number of read-only transactions committed                                                                       |
| trx_nl_ro_commits                          | transaction         | counter        | Number of non-locking auto-commit read-only transactions committed                                               |
| trx_commits_insert_update                  | transaction         | counter        | Number of transactions committed with inserts and updates                                                        |
| trx_rollbacks                              | transaction         | counter        | Number of transactions rolled back                                                                               |
| trx_rollbacks_savepoint                    | transaction         | counter        | Number of transactions rolled back to savepoint                                                                  |
| trx_rseg_history_len                       | transaction         | value          | Length of the TRX_RSEG_HISTORY list                                                                              |
| trx_undo_slots_used                        | transaction         | counter        | Number of undo slots used                                                                                        |
| trx_undo_slots_cached                      | transaction         | counter        | Number of undo slots cached                                                                                      |
| trx_rseg_current_size                      | transaction         | value          | Current rollback segment size in pages                                                                           |
| purge_del_mark_records                     | purge               | counter        | Number of delete-marked rows purged                                                                              |
| purge_upd_exist_or_extern_records          | purge               | counter        | Number of purges on updates of existing records and updates on delete marked record with externally stored field |
| purge_invoked                              | purge               | counter        | Number of times purge was invoked                                                                                |
| purge_undo_log_pages                       | purge               | counter        | Number of undo log pages handled by the purge                                                                    |
| purge_dml_delay_usec                       | purge               | value          | Microseconds DML to be delayed due to purge lagging                                                              |
| purge_stop_count                           | purge               | value          | Number of times purge was stopped                                                                                |
| purge_resume_count                         | purge               | value          | Number of times purge was resumed                                                                                |
| log_checkpoints                            | recovery            | counter        | Number of checkpoints                                                                                            |
| log_lsn_last_flush                         | recovery            | value          | LSN of Last flush                                                                                                |
| log_lsn_last_checkpoint                    | recovery            | value          | LSN at last checkpoint                                                                                           |
| log_lsn_current                            | recovery            | value          | Current LSN value                                                                                                |
| log_lsn_checkpoint_age                     | recovery            | value          | Current LSN value minus LSN at last checkpoint                                                                   |
| log_lsn_buf_pool_oldest                    | recovery            | value          | The oldest modified block LSN in the buffer pool                                                                 |
| log_max_modified_age_async                 | recovery            | value          | Maximum LSN difference; when exceeded, start asynchronous preflush                                               |
| log_pending_log_flushes                    | recovery            | value          | Pending log flushes                                                                                              |
| log_pending_checkpoint_writes              | recovery            | value          | Pending checkpoints                                                                                              |
| log_num_log_io                             | recovery            | value          | Number of log I/Os                                                                                               |
| log_waits                                  | recovery            | status_counter | Number of log waits due to small log buffer (innodb_log_waits)                                                   |
| log_write_requests                         | recovery            | status_counter | Number of log write requests (innodb_log_write_requests)                                                         |
| log_writes                                 | recovery            | status_counter | Number of log writes (innodb_log_writes)                                                                         |
| log_padded                                 | recovery            | status_counter | Bytes of log padded for log write ahead                                                                          |
| compress_pages_compressed                  | compression         | counter        | Number of pages compressed                                                                                       |
| compress_pages_decompressed                | compression         | counter        | Number of pages decompressed                                                                                     |
| compression_pad_increments                 | compression         | counter        | Number of times padding is incremented to avoid compression failures                                             |
| compression_pad_decrements                 | compression         | counter        | Number of times padding is decremented due to good compressibility                                               |
| compress_saved                             | compression         | counter        | Number of bytes saved by page compression                                                                        |
| compress_pages_page_compressed             | compression         | counter        | Number of pages compressed by page compression                                                                   |
| compress_page_compressed_trim_op           | compression         | counter        | Number of TRIM operation performed by page compression                                                           |
| compress_pages_page_decompressed           | compression         | counter        | Number of pages decompressed by page compression                                                                 |
| compress_pages_page_compression_error      | compression         | counter        | Number of page compression errors                                                                                |
| compress_pages_encrypted                   | compression         | counter        | Number of pages encrypted                                                                                        |
| compress_pages_decrypted                   | compression         | counter        | Number of pages decrypted                                                                                        |
| index_page_splits                          | index               | counter        | Number of index page splits                                                                                      |
| index_page_merge_attempts                  | index               | counter        | Number of index page merge attempts                                                                              |
| index_page_merge_successful                | index               | counter        | Number of successful index page merges                                                                           |
| index_page_reorg_attempts                  | index               | counter        | Number of index page reorganization attempts                                                                     |
| index_page_reorg_successful                | index               | counter        | Number of successful index page reorganizations                                                                  |
| index_page_discards                        | index               | counter        | Number of index pages discarded                                                                                  |
| adaptive_hash_searches                     | adaptive_hash_index | status_counter | Number of successful searches using Adaptive Hash Index                                                          |
| adaptive_hash_searches_btree               | adaptive_hash_index | status_counter | Number of searches using B-tree on an index search                                                               |
| adaptive_hash_pages_added                  | adaptive_hash_index | counter        | Number of index pages on which the Adaptive Hash Index is built                                                  |
| adaptive_hash_pages_removed                | adaptive_hash_index | counter        | Number of index pages whose corresponding Adaptive Hash Index entries were removed                               |
| adaptive_hash_rows_added                   | adaptive_hash_index | counter        | Number of Adaptive Hash Index rows added                                                                         |
| adaptive_hash_rows_removed                 | adaptive_hash_index | counter        | Number of Adaptive Hash Index rows removed                                                                       |
| adaptive_hash_rows_deleted_no_hash_entry   | adaptive_hash_index | counter        | Number of rows deleted that did not have corresponding Adaptive Hash Index entries                               |
| adaptive_hash_rows_updated                 | adaptive_hash_index | counter        | Number of Adaptive Hash Index rows updated                                                                       |
| file_num_open_files                        | file_system         | value          | Number of files currently open (innodb_num_open_files)                                                           |
| ibuf_merges_insert                         | change_buffer       | status_counter | Number of inserted records merged by change buffering                                                            |
| ibuf_merges_delete_mark                    | change_buffer       | status_counter | Number of deleted records merged by change buffering                                                             |
| ibuf_merges_delete                         | change_buffer       | status_counter | Number of purge records merged by change buffering                                                               |
| ibuf_merges_discard_insert                 | change_buffer       | status_counter | Number of insert merged operations discarded                                                                     |
| ibuf_merges_discard_delete_mark            | change_buffer       | status_counter | Number of deleted merged operations discarded                                                                    |
| ibuf_merges_discard_delete                 | change_buffer       | status_counter | Number of purge merged  operations discarded                                                                     |
| ibuf_merges                                | change_buffer       | status_counter | Number of change buffer merges                                                                                   |
| ibuf_size                                  | change_buffer       | status_counter | Change buffer size in pages                                                                                      |
| innodb_master_thread_sleeps                | server              | counter        | Number of times (seconds) master thread sleeps                                                                   |
| innodb_activity_count                      | server              | status_counter | Current server activity count                                                                                    |
| innodb_master_active_loops                 | server              | counter        | Number of times master thread performs its tasks when server is active                                           |
| innodb_master_idle_loops                   | server              | counter        | Number of times master thread performs its tasks when server is idle                                             |
| innodb_log_flush_usec                      | server              | counter        | Time (in microseconds) spent to flush log records                                                                |
| innodb_dict_lru_usec                       | server              | counter        | Time (in microseconds) spent to process DICT LRU list                                                            |
| innodb_dict_lru_count_active               | server              | counter        | Number of tables evicted from DICT LRU list in the active loop                                                   |
| innodb_dict_lru_count_idle                 | server              | counter        | Number of tables evicted from DICT LRU list in the idle loop                                                     |
| innodb_dblwr_writes                        | server              | status_counter | Number of doublewrite operations that have been performed (innodb_dblwr_writes)                                  |
| innodb_dblwr_pages_written                 | server              | status_counter | Number of pages that have been written for doublewrite operations (innodb_dblwr_pages_written)                   |
| innodb_page_size                           | server              | value          | InnoDB page size in bytes (innodb_page_size)                                                                     |
| dml_reads                                  | dml                 | status_counter | Number of rows read                                                                                              |
| dml_inserts                                | dml                 | status_counter | Number of rows inserted                                                                                          |
| dml_deletes                                | dml                 | status_counter | Number of rows deleted                                                                                           |
| dml_updates                                | dml                 | status_counter | Number of rows updated                                                                                           |
| dml_system_reads                           | dml                 | status_counter | Number of system rows read                                                                                       |
| dml_system_inserts                         | dml                 | status_counter | Number of system rows inserted                                                                                   |
| dml_system_deletes                         | dml                 | status_counter | Number of system rows deleted                                                                                    |
| dml_system_updates                         | dml                 | status_counter | Number of system rows updated                                                                                    |
| ddl_background_drop_indexes                | ddl                 | counter        | Number of indexes waiting to be dropped after failed index creation                                              |
| ddl_online_create_index                    | ddl                 | counter        | Number of indexes being created online                                                                           |
| ddl_pending_alter_table                    | ddl                 | counter        | Number of ALTER TABLE, CREATE INDEX, DROP INDEX in progress                                                      |
| ddl_sort_file_alter_table                  | ddl                 | counter        | Number of sort files created during alter table                                                                  |
| ddl_log_file_alter_table                   | ddl                 | counter        | Number of log files created during alter table                                                                   |
| icp_attempts                               | icp                 | counter        | Number of attempts for index push-down condition checks                                                          |
| icp_no_match                               | icp                 | counter        | Index push-down condition does not match                                                                         |
| icp_out_of_range                           | icp                 | counter        | Index push-down condition out of range                                                                           |
| icp_match                                  | icp                 | counter        | Index push-down condition matches                                                                                |
+--------------------------------------------+---------------------+----------------+------------------------------------------------------------------------------------------------------------------+
216 rows in set (0.000 sec)

1.1.1.2.9.1.1.1.20 Information Schema INNODB_MUTEXES Table

The INNODB_MUTEXES table monitors mutex and rw locks waits. It has the following columns:

ColumnDescription
NAMEName of the lock, as it appears in the source code.
CREATE_FILEFile name of the mutex implementation.
CREATE_LINELine number of the mutex implementation.
OS_WAITSHow many times the mutex occurred.

The CREATE_FILE and CREATE_LINE columns depend on the InnoDB/XtraDB version.

Note that since MariaDB 10.2.2, the table has only been providing information about rw_lock_t, not any mutexes. From MariaDB 10.2.2 until MariaDB 10.2.32, MariaDB 10.3.23, MariaDB 10.4.13 and MariaDB 10.5.1, the NAME column was not populated (MDEV-21636).

The SHOW ENGINE INNODB STATUS statement provides similar information.

Examples

SELECT * FROM INNODB_MUTEXES;
+------------------------------+---------------------+-------------+----------+
| NAME                         | CREATE_FILE         | CREATE_LINE | OS_WAITS |
+------------------------------+---------------------+-------------+----------+
| &dict_sys->mutex             | dict0dict.cc        |         989 |        2 |
| &buf_pool->flush_state_mutex | buf0buf.cc          |        1388 |        1 |
| &log_sys->checkpoint_lock    | log0log.cc          |        1014 |        2 |
| &block->lock                 | combined buf0buf.cc |        1120 |        1 |
+------------------------------+---------------------+-------------+----------+

1.1.1.2.9.1.1.1.21 Information Schema INNODB_SYS_COLUMNS Table

The Information Schema INNODB_SYS_COLUMNS table contains information about InnoDB fields.

The PROCESS privilege is required to view the table.

It has the following columns:

ColumnDescription
TABLE_IDTable identifier, matching the value from INNODB_SYS_TABLES.TABLE_ID.
NAMEColumn name.
POSOrdinal position of the column in the table, starting from 0. This value is adjusted when columns are added or removed.
MTYPENumeric column type identifier, (see the table below for an explanation of its values).
PRTYPEBinary value of the InnoDB precise type, representing the data type, character set code and nullability.
LENColumn length. For multi-byte character sets, represents the length in bytes.

The column MTYPE uses a numeric column type identifier, which has the following values:

Column Type IdentifierDescription
1VARCHAR
2CHAR
3FIXBINARY
4BINARY
5BLOB
6INT
7SYS_CHILD
8SYS
9FLOAT
10DOUBLE
11DECIMAL
12VARMYSQL
13MYSQL

Example

SELECT * FROM information_schema.INNODB_SYS_COLUMNS LIMIT 3\G
*************************** 1. row ***************************
TABLE_ID: 11
    NAME: ID
     POS: 0
   MTYPE: 1
  PRTYPE: 524292
     LEN: 0
*************************** 2. row ***************************
TABLE_ID: 11
    NAME: FOR_NAME 
     POS: 0
   MTYPE: 1
  PRTYPE: 524292
    LEN: 0
*************************** 3. row ***************************
TABLE_ID: 11
    NAME: REF_NAME 
     POS: 0
   MTYPE: 1
  PRTYPE: 524292
     LEN: 0
3 rows in set (0.00 sec)

1.1.1.2.9.1.1.1.22 Information Schema INNODB_SYS_DATAFILES Table

MariaDB until 10.5

The INNODB_SYS_DATAFILES table was added in MariaDB 10.0.4, and removed in MariaDB 10.6.0.

The Information Schema INNODB_SYS_DATAFILES table contains information about InnoDB datafile paths. It was intended to provide metadata for tablespaces inside InnoDB tables, which was never implemented in MariaDB and was removed in MariaDB 10.6. The PROCESS privilege is required to view the table.

It contains the following columns:

ColumnDescription
SPACENumeric tablespace. Matches the INNODB_SYS_TABLES.SPACE value.
PATHTablespace datafile path.

Example

SELECT * FROM INNODB_SYS_DATAFILES;
+-------+--------------------------------+
| SPACE | PATH                           |
+-------+--------------------------------+
|    19 | ./test/t2.ibd                  |
|    20 | ./test/t3.ibd                  |
...
|    68 | ./test/animals.ibd             |
|    69 | ./test/animal_count.ibd        |
|    70 | ./test/t.ibd                   |
+-------+--------------------------------+

1.1.1.2.9.1.1.1.23 Information Schema INNODB_SYS_FIELDS Table

The Information Schema INNODB_SYS_FIELDS table contains information about fields that are part of an InnoDB index.

The PROCESS privilege is required to view the table.

It has the following columns:

ColumnDescription
INDEX_IDIndex identifier, matching the value from INNODB_SYS_INDEXES.INDEX_ID.
NAMEField name, matching the value from INNODB_SYS_COLUMNS.NAME.
POSOrdinal position of the field within the index, starting from 0. This is adjusted as columns are removed.

Example

SELECT * FROM information_schema.INNODB_SYS_FIELDS LIMIT 3\G
*************************** 1. row ***************************
INDEX_ID: 11
    NAME: ID
     POS: 0
*************************** 2. row ***************************
INDEX_ID: 12
    NAME: FOR_NAME 
     POS: 0
*************************** 3. row ***************************
INDEX_ID: 13
    NAME: REF_NAME 
     POS: 0
3 rows in set (0.00 sec)

1.1.1.2.9.1.1.1.24 Information Schema INNODB_SYS_FOREIGN Table

The Information Schema INNODB_SYS_FOREIGN table contains information about InnoDB foreign keys.

The PROCESS privilege is required to view the table.

It has the following columns:

ColumnDescription
IDDatabase name and foreign key name.
FOR_NAMEDatabase and table name of the foreign key child.
REF_NAMEDatabase and table name of the foreign key parent.
N_COLSNumber of foreign key index columns.
TYPEBit flag providing information about the foreign key.

The TYPE column provides a bit flag with information about the foreign key. This information is OR'ed together to read:

Bit FlagDescription
1ON DELETE CASCADE
2ON UPDATE SET NULL
4ON UPDATE CASCADE
8ON UPDATE SET NULL
16ON DELETE NO ACTION
32ON UPDATE NO ACTION

Example

SELECT * FROM INNODB_SYS_FOREIGN\G
*************************** 1. row ***************************
      ID: mysql/innodb_index_stats_ibfk_1
FOR_NAME: mysql/innodb_index_stats
REF_NAME: mysql/innodb_table_stats
  N_COLS: 2
    TYPE: 0
...

1.1.1.2.9.1.1.1.25 Information Schema INNODB_SYS_FOREIGN_COLS Table

The Information Schema INNODB_SYS_FOREIGN_COLS table contains information about InnoDB foreign key columns.

The PROCESS privilege is required to view the table.

It has the following columns:

ColumnDescription
IDForeign key index associated with this column, matching the INNODB_SYS_FOREIGN.ID field.
FOR_COL_NAMEChild column name.
REF_COL_NAMEParent column name.
POSOrdinal position of the column in the table, starting from 0.

1.1.1.2.9.1.1.1.26 Information Schema INNODB_SYS_INDEXES Table

The Information Schema INNODB_SYS_INDEXES table contains information about InnoDB indexes.

The PROCESS privilege is required to view the table.

It has the following columns:

FieldTypeNullKeyDefaultDescription
INDEX_IDbigint(21) unsignedNO0A unique index identifier.
NAMEvarchar(64)NOIndex name, lowercase for all user-created indexes, or uppercase for implicitly-created indexes; PRIMARY (primary key), GEN_CLUST_INDEX (index representing primary key where there isn't one), ID_IND, FOR_IND (validating foreign key constraint) , REF_IND.
TABLE_IDbigint(21) unsignedNO0Table identifier, matching the value from INNODB_SYS_TABLES.TABLE_ID.
TYPEint(11)NO0Numeric type identifier; one of 0 (secondary index), 1 (clustered index), 2 (unique index), 3 (primary index), 32 (full-text index).
N_FIELDSint(11)NO0Number of columns in the index. GEN_CLUST_INDEX's have a value of 0 as the index is not based on an actual column in the table.
PAGE_NOint(11)NO0Index B-tree's root page number. -1 (unused) for full-text indexes, as they are laid out over several auxiliary tables.
SPACEint(11)NO0Tablespace identifier where the index resides. 0 represents the InnoDB system tablespace, while any other value represents a table created in file-per-table mode (see the innodb_file_per_table system variable). Remains unchanged after a TRUNCATE TABLE statement, and not necessarily unique.
MERGE_THRESHOLDint(11)NO0

Example

SELECT * FROM information_schema.INNODB_SYS_INDEXES LIMIT 3\G
*************************** 1. row ***************************
       INDEX_ID: 11
           NAME: ID_IND
       TABLE_ID: 11
           TYPE: 3
       N_FIELDS: 1
        PAGE_NO: 302
          SPACE: 0
MERGE_THRESHOLD: 50
*************************** 2. row ***************************
       INDEX_ID: 12
           NAME: FOR_IND
       TABLE_ID: 11
           TYPE: 0
       N_FIELDS: 1
        PAGE_NO: 303
          SPACE: 0
MERGE_THRESHOLD: 50
*************************** 3. row ***************************
       INDEX_ID: 13
           NAME: REF_IND
       TABLE_ID: 11
           TYPE: 3
       N_FIELDS: 1
        PAGE_NO: 304
          SPACE: 0
MERGE_THRESHOLD: 50
3 rows in set (0.00 sec)

1.1.1.2.9.1.1.1.27 Information Schema INNODB_SYS_SEMAPHORE_WAITS Table

The Information Schema INNODB_SYS_SEMAPHORE_WAITS table is meant to contain information about current semaphore waits. At present it is not correctly populated. See MDEV-21330.

The PROCESS privilege is required to view the table.

It contains the following columns:

ColumnDescription
THREAD_IDThread id waiting for semaphore
OBJECT_NAMESemaphore name
FILEFile name where semaphore was requested
LINELine number on above file
WAIT_TIMEWait time
WAIT_OBJECT
WAIT_TYPEObject type (mutex, rw-lock)
HOLDER_THREAD_IDHolder thread id
HOLDER_FILEFile name where semaphore was acquired
HOLDER_LINELine number for above
CREATED_FILECreation file name
CREATED_LINELine number for above
WRITER_THREADLast write request thread id
RESERVATION_MODEReservation mode (shared, exclusive)
READERSNumber of readers if only shared mode
WAITERS_FLAGFlags
LOCK_WORDLock word (for developers)
LAST_READER_FILERemoved
LAST_READER_LINERemoved
LAST_WRITER_FILELast writer file name
LAST_WRITER_LINEAbove line number
OS_WAIT_COUNTWait count

1.1.1.2.9.1.1.1.28 Information Schema INNODB_SYS_TABLES Table

The Information Schema INNODB_SYS_TABLES table contains information about InnoDB tables.

The PROCESS privilege is required to view the table.

It has the following columns:

FieldTypeNullKeyDefaultDescription
TABLE_IDbigint(21) unsignedNO0Unique InnoDB table identifier.
NAMEvarchar(655)NODatabase and table name, or the uppercase InnoDB system table name.
FLAGint(11)NO0See Flag below
N_COLSint(11) unsigned (>= MariaDB 10.5)
int(11) (<= MariaDB 10.4)		NO0Number of columns in the table.
SPACEint(11) unsigned (>= MariaDB 10.5)
int(11) (<= MariaDB 10.4)		NO0Tablespace identifier where the index resides. 0 represents the InnoDB system tablespace, while any other value represents a table created in file-per-table mode (see the innodb_file_per_table system variable). Remains unchanged after a TRUNCATE TABLE statement.
FILE_FORMATvarchar(10)YESNULLInnoDB file format (Antelope or Barracuda). Removed in MariaDB 10.3.
ROW_FORMATenum('Redundant', 'Compact', 'Compressed', 'Dynamic') (>= MariaDB 10.5)
varchar(12) (<= MariaDB 10.4)		YESNULLInnoDB storage format (Compact, Redundant, Dynamic, or Compressed).
ZIP_PAGE_SIZEint(11) unsignedNO0For Compressed tables, the zipped page size.
SPACE_TYPEenum('Single','System') (>= MariaDB 10.5)
varchar(10) (<= MariaDB 10.4)		YESNULL

Flag

The flag field returns the dict_table_t::flags that correspond to the data dictionary record.

BitDescription
0Set if ROW_FORMAT is not REDUNDANT.
1 to 40, except for ROW_FORMAT=COMPRESSED, where they will determine the KEY_BLOCK_SIZE (the compressed page size).
5Set for ROW_FORMAT=DYNAMIC or ROW_FORMAT=COMPRESSED.
6Set if the DATA DIRECTORY attribute was present when the table was originally created.
7Set if the page_compressed attribute is present.
8 to 11Determine the page_compression_level.
12 13Normally 00, but 11 for "no-rollback tables" (MariaDB 10.3 CREATE SEQUENCE). In MariaDB 10.1, these bits could be 01 or 10 for ATOMIC_WRITES=ON or ATOMIC_WRITES=OFF.

Note that the table flags returned here are not the same as tablespace flags (FSP_SPACE_FLAGS).

Example

SELECT * FROM information_schema.INNODB_SYS_TABLES LIMIT 2\G
*************************** 1. row ***************************
     TABLE_ID: 14
         NAME: SYS_DATAFILES
         FLAG: 0
       N_COLS: 5
        SPACE: 0
  FILE_FORMAT: Antelope
   ROW_FORMAT: Redundant
ZIP_PAGE_SIZE: 0
   SPACE_TYPE: System
*************************** 2. row ***************************
     TABLE_ID: 11
         NAME: SYS_FOREIGN
         FLAG: 0
       N_COLS: 7
        SPACE: 0
  FILE_FORMAT: Antelope
   ROW_FORMAT: Redundant
ZIP_PAGE_SIZE: 0
   SPACE_TYPE: System
2 rows in set (0.00 sec)

See Also

1.1.1.2.9.1.1.1.29 Information Schema INNODB_SYS_TABLESPACES Table

The Information Schema INNODB_SYS_TABLESPACES table contains information about InnoDB tablespaces. Until MariaDB 10.5 it was based on the internal SYS_TABLESPACES table. This internal table was removed in MariaDB 10.6.0, so this Information Schema table has been repurposed to directly reflect the filesystem (fil_system.space_list).

The PROCESS privilege is required to view the table.

It has the following columns:

ColumnDescription
SPACEUnique InnoDB tablespace identifier.
NAMEDatabase and table name separated by a backslash, or the uppercase InnoDB system table name.
FLAG1 if a DATA DIRECTORY option has been specified in CREATE TABLE, otherwise 0.
FILE_FORMATInnoDB file format.
ROW_FORMATInnoDB storage format used for this tablespace. If the Antelope file format is used, this value is always Compact or Redundant.
PAGE_SIZEPage size in bytes for this tablespace. Until MariaDB 10.5.0, this was the value of the innodb_page_size variable. From MariaDB 10.6.0, contains the physical page size of a page (previously ZIP_PAGE_SIZE).
ZIP_PAGE_SIZEZip page size for this tablespace. Removed in MariaDB 10.6.0.
SPACE_TYPETablespace type. Can be General for general tablespaces or Single for file-per-table tablespaces. Introduced MariaDB 10.2.1. Removed MariaDB 10.5.0.
FS_BLOCK_SIZEFile system block size. Introduced MariaDB 10.2.1.
FILE_SIZEMaximum size of the file, uncompressed. Introduced MariaDB 10.2.1.
ALLOCATED_SIZEActual size of the file as per space allocated on disk. Introduced MariaDB 10.2.1.
FILENAMETablespace datafile path, previously part of the INNODB_SYS_DATAFILES table. Added in MariaDB 10.6.0.

Examples

MariaDB 10.4:

DESC information_schema.innodb_sys_tablespaces;
+----------------+---------------------+------+-----+---------+-------+
| Field          | Type                | Null | Key | Default | Extra |
+----------------+---------------------+------+-----+---------+-------+
| SPACE          | int(11) unsigned    | NO   |     | 0       |       |
| NAME           | varchar(655)        | NO   |     |         |       |
| FLAG           | int(11) unsigned    | NO   |     | 0       |       |
| FILE_FORMAT    | varchar(10)         | YES  |     | NULL    |       |
| ROW_FORMAT     | varchar(22)         | YES  |     | NULL    |       |
| PAGE_SIZE      | int(11) unsigned    | NO   |     | 0       |       |
| ZIP_PAGE_SIZE  | int(11) unsigned    | NO   |     | 0       |       |
| SPACE_TYPE     | varchar(10)         | YES  |     | NULL    |       |
| FS_BLOCK_SIZE  | int(11) unsigned    | NO   |     | 0       |       |
| FILE_SIZE      | bigint(21) unsigned | NO   |     | 0       |       |
| ALLOCATED_SIZE | bigint(21) unsigned | NO   |     | 0       |       |
+----------------+---------------------+------+-----+---------+-------+

From MariaDB 10.4:

SELECT * FROM information_schema.INNODB_SYS_TABLESPACES LIMIT 2\G
*************************** 1. row ***************************
         SPACE: 2
          NAME: mysql/innodb_table_stats
          FLAG: 33
   FILE_FORMAT: Barracuda
    ROW_FORMAT: Dynamic
     PAGE_SIZE: 16384
 ZIP_PAGE_SIZE: 0
    SPACE_TYPE: Single
 FS_BLOCK_SIZE: 4096
     FILE_SIZE: 98304
ALLOCATED_SIZE: 98304
*************************** 2. row ***************************
         SPACE: 3
          NAME: mysql/innodb_index_stats
          FLAG: 33
   FILE_FORMAT: Barracuda
    ROW_FORMAT: Dynamic
     PAGE_SIZE: 16384
 ZIP_PAGE_SIZE: 0
    SPACE_TYPE: Single
 FS_BLOCK_SIZE: 4096
     FILE_SIZE: 98304
ALLOCATED_SIZE: 98304

1.1.1.2.9.1.1.1.30 Information Schema INNODB_SYS_TABLESTATS Table

The Information Schema INNODB_SYS_TABLESTATS table contains InnoDB status information. It can be used for developing new performance-related extensions, or high-level performance monitoring.

The PROCESS privilege is required to view the table.

Note that the MySQL InnoDB and Percona XtraDB versions of the tables differ (see XtraDB and InnoDB).

It contains the following columns:

ColumnDescription
TABLE_IDTable ID, matching the INNODB_SYS_TABLES.TABLE_ID value.
SCHEMADatabase name (XtraDB only).
NAMETable name, matching the INNODB_SYS_TABLES.NAME value.
STATS_INITIALIZEDInitialized if statistics have already been collected, otherwise Uninitialized.
NUM_ROWSEstimated number of rows currently in the table. Updated after each statement modifying the data, but uncommited transactions mean it may not be accurate.
CLUST_INDEX_SIZENumber of pages on disk storing the clustered index, holding InnoDB table data in primary key order, or NULL if not statistics yet collected.
OTHER_INDEX_SIZENumber of pages on disk storing secondary indexes for the table, or NULL if not statistics yet collected.
MODIFIED_COUNTERNumber of rows modified by statements modifying data.
AUTOINCAuto_increment value.
REF_COUNTCountdown to zero, when table metadata can be removed from the table cache. (InnoDB only)
MYSQL_HANDLES_OPENED(XtraDB only).

1.1.1.2.9.1.1.1.31 Information Schema INNODB_SYS_VIRTUAL Table

MariaDB starting with 10.2

The INNODB_SYS_VIRTUAL table was added in MariaDB 10.2.

The Information Schema INNODB_SYS_VIRTUAL table contains information about base columns of virtual columns. The PROCESS privilege is required to view the table.

It contains the following columns:

FieldTypeNullKeyDefaultDescription
TABLE_IDbigint(21) unsignedNO0
POSint(11) unsignedNO0
BASE_POSint(11) unsignedNO0

1.1.1.2.9.1.1.1.32 Information Schema INNODB_TABLESPACES_ENCRYPTION Table

The Information Schema INNODB_TABLESPACES_ENCRYPTION table contains metadata about encrypted InnoDB tablespaces. When you enable encryption for an InnoDB tablespace, an entry for the tablespace is added to this table. If you later disable encryption for the InnoDB tablespace, then the row still remains in this table, but the ENCRYPTION_SCHEME and CURRENT_KEY_VERSION columns will be set to 0.

Viewing this table requires the PROCESS privilege, although a bug in versions before MariaDB 10.1.46, 10.2.33, 10.3.24, 10.4.14 and 10.5.5 mean the SUPER privilege was required (MDEV-23003).

It has the following columns:

ColumnDescriptionAdded
SPACEInnoDB tablespace ID.
NAMEPath to the InnoDB tablespace file, without the extension.
ENCRYPTION_SCHEMEKey derivation algorithm. Only 1 is currently used to represent an algorithm. If this value is 0, then the tablespace is unencrypted.
KEYSERVER_REQUESTSNumber of times InnoDB has had to request a key from the encryption key management plugin. The three most recent keys are cached internally.
MIN_KEY_VERSIONMinimum key version used to encrypt a page in the tablespace. Different pages may be encrypted with different key versions.
CURRENT_KEY_VERSIONKey version that will be used to encrypt pages. If this value is 0, then the tablespace is unencrypted.
KEY_ROTATION_PAGE_NUMBERPage that a background encryption thread is currently rotating. If key rotation is not enabled, then the value will be NULL.
KEY_ROTATION_MAX_PAGE_NUMBERWhen a background encryption thread starts rotating a tablespace, the field contains its current size. If key rotation is not enabled, then the value will be NULL.
CURRENT_KEY_IDKey ID for the encryption key currently in use.MariaDB 10.1.13
ROTATING_OR_FLUSHINGCurrent key rotation status. If this value is 1, then the background encryption threads are working on the tablespace. See MDEV-11738.MariaDB 10.2.5, MariaDB 10.1.23

When the InnoDB system tablespace is encrypted, it is represented in this table with the special name: innodb_system.

Example

SELECT * FROM information_schema.INNODB_TABLESPACES_ENCRYPTION 
WHERE NAME LIKE 'db_encrypt%';
+-------+----------------------------------------------+-------------------+--------------------+-----------------+---------------------+--------------------------+------------------------------+
| SPACE | NAME                                         | ENCRYPTION_SCHEME | KEYSERVER_REQUESTS | MIN_KEY_VERSION | CURRENT_KEY_VERSION | KEY_ROTATION_PAGE_NUMBER | KEY_ROTATION_MAX_PAGE_NUMBER |
+-------+----------------------------------------------+-------------------+--------------------+-----------------+---------------------+--------------------------+------------------------------+
|    18 | db_encrypt/t_encrypted_existing_key          |                 1 |                  1 |               1 |                   1 |                     NULL |                         NULL |
|    19 | db_encrypt/t_not_encrypted_existing_key      |                 1 |                  0 |               1 |                   1 |                     NULL |                         NULL |
|    20 | db_encrypt/t_not_encrypted_non_existing_key  |                 1 |                  0 |      4294967295 |          4294967295 |                     NULL |                         NULL |
|    21 | db_encrypt/t_default_encryption_existing_key |                 1 |                  1 |               1 |                   1 |                     NULL |                         NULL |
|    22 | db_encrypt/t_encrypted_default_key           |                 1 |                  1 |               1 |                   1 |                     NULL |                         NULL |
|    23 | db_encrypt/t_not_encrypted_default_key       |                 1 |                  0 |               1 |                   1 |                     NULL |                         NULL |
|    24 | db_encrypt/t_defaults                        |                 1 |                  1 |               1 |                   1 |                     NULL |                         NULL |
+-------+----------------------------------------------+-------------------+--------------------+-----------------+---------------------+--------------------------+------------------------------+
7 rows in set (0.00 sec)

See Also

1.1.1.2.9.1.1.1.33 Information Schema INNODB_TABLESPACES_SCRUBBING Table

MariaDB 10.1.3 - 10.5.1

InnoDB and XtraDB data scrubbing was introduced in MariaDB 10.1.3. The table was removed in MariaDB 10.5.2 - see MDEV-15528.

The Information Schema INNODB_TABLESPACES_SCRUBBING table contains data scrubbing information.

The PROCESS privilege is required to view the table.

It has the following columns:

ColumnDescription
SPACEInnoDB table space id number.
NAMEPath to the table space file, without the extension.
COMPRESSEDThe compressed page size, or zero if uncompressed.
LAST_SCRUB_COMPLETEDDate and time when the last scrub was completed, or NULL if never been performed.
CURRENT_SCRUB_STARTEDDate and time when the current scrub started, or NULL if never been performed.
CURRENT_SCRUB_ACTIVE_THREADSNumber of threads currently scrubbing the tablespace.
CURRENT_SCRUB_PAGE_NUMBERPage that the scrubbing thread is currently scrubbing, or NULL if not enabled.
CURRENT_SCRUB_MAX_PAGE_NUMBERWhen a scrubbing starts rotating a table space, the field contains its current size. NULL if not enabled.

Example

SELECT * FROM information_schema.INNODB_TABLESPACES_SCRUBBING LIMIT 1\G
*************************** 1. row ***************************
                        SPACE: 1
                         NAME: mysql/innodb_table_stats
                   COMPRESSED: 0
         LAST_SCRUB_COMPLETED: NULL
        CURRENT_SCRUB_STARTED: NULL
    CURRENT_SCRUB_PAGE_NUMBER: NULL
CURRENT_SCRUB_MAX_PAGE_NUMBER: 0
         ROTATING_OR_FLUSHING: 0
1 rows in set (0.00 sec)

1.1.1.2.9.1.1.1.34 Information Schema INNODB_TRX Table

The Information Schema INNODB_TRX table stores information about all currently executing InnoDB transactions.

It has the following columns:

ColumnDescription
TRX_IDUnique transaction ID number.
TRX_STATETransaction execution state; one of RUNNING, LOCK WAIT, ROLLING BACK or COMMITTING.
TRX_STARTEDTime that the transaction started.
TRX_REQUESTED_LOCK_IDIf TRX_STATE is LOCK_WAIT, the INNODB_LOCKS.LOCK_ID value of the lock being waited on. NULL if any other state.
TRX_WAIT_STARTEDIf TRX_STATE is LOCK_WAIT, the time the transaction started waiting for the lock, otherwise NULL.
TRX_WEIGHTTransaction weight, based on the number of locked rows and the number of altered rows. To resolve deadlocks, lower weighted transactions are rolled back first. Transactions that have affected non-transactional tables are always treated as having a heavier weight.
TRX_MYSQL_THREAD_IDThread ID from the PROCESSLIST table (note that the locking and transaction information schema tables use a different snapshot from the processlist, so records may appear in one but not the other).
TRX_QUERYSQL that the transaction is currently running.
TRX_OPERATION_STATETransaction's current state, or NULL.
TRX_TABLES_IN_USENumber of InnoDB tables currently being used for processing the current SQL statement.
TRX_TABLES_LOCKEDNumber of InnoDB tables that that have row locks held by the current SQL statement.
TRX_LOCK_STRUCTSNumber of locks reserved by the transaction.
TRX_LOCK_MEMORY_BYTESTotal size in bytes of the memory used to hold the lock structures for the current transaction in memory.
TRX_ROWS_LOCKEDNumber of rows the current transaction has locked. locked by this transaction. An approximation, and may include rows not visible to the current transaction that are delete-marked but physically present.
TRX_ROWS_MODIFIEDNumber of rows added or changed in the current transaction.
TRX_CONCURRENCY_TICKETSIndicates how much work the current transaction can do before being swapped out, see the innodb_concurrency_tickets system variable.
TRX_ISOLATION_LEVELIsolation level of the current transaction.
TRX_UNIQUE_CHECKSWhether unique checks are on or off for the current transaction. Bulk data are a case where unique checks would be off.
TRX_FOREIGN_KEY_CHECKSWhether foreign key checks are on or off for the current transaction. Bulk data are a case where foreign keys checks would be off.
TRX_LAST_FOREIGN_KEY_ERRORError message for the most recent foreign key error, or NULL if none.
TRX_ADAPTIVE_HASH_LATCHEDWhether the adaptive hash index is locked by the current transaction or not. One transaction at a time can change the adaptive hash index.
TRX_ADAPTIVE_HASH_TIMEOUTWhether the adaptive hash index search latch shoild be relinquished immediately or reserved across all MariaDB calls. 0 if there is no contention on the adaptive hash index, in which case the latch is reserved until completion, otherwise counts down to zero and the latch is released after each row lookup.
TRX_IS_READ_ONLY1 if a read-only transaction, otherwise 0.
TRX_AUTOCOMMIT_NON_LOCKING1 if the transaction only contains this one statement, that is, a SELECT statement not using FOR UPDATE or LOCK IN SHARED MODE, and with autocommit on. If this and TRX_IS_READ_ONLY are both 1, the transaction can be optimized by the storrage engine to reduce some overheads

The table is often used in conjunction with the INNODB_LOCKS and INNODB_LOCK_WAITS tables to diagnose problematic locks and transactions.

XA transactions are not stored in this table. To see them, XA RECOVER can be used.

Example

-- session 1
START TRANSACTION;
UPDATE t SET id = 15 WHERE id = 10;

-- session 2
DELETE FROM t WHERE id = 10;

-- session 1
USE information_schema;
SELECT l.*, t.*
    FROM information_schema.INNODB_LOCKS l
    JOIN information_schema.INNODB_TRX t
        ON l.lock_trx_id = t.trx_id
    WHERE trx_state = 'LOCK WAIT' \G
*************************** 1. row ***************************
                   lock_id: 840:40:3:2
               lock_trx_id: 840
                 lock_mode: X
                 lock_type: RECORD
                lock_table: `test`.`t`
                lock_index: PRIMARY
                lock_space: 40
                 lock_page: 3
                  lock_rec: 2
                 lock_data: 10
                    trx_id: 840
                 trx_state: LOCK WAIT
               trx_started: 2019-12-23 18:43:46
     trx_requested_lock_id: 840:40:3:2
          trx_wait_started: 2019-12-23 18:43:46
                trx_weight: 2
       trx_mysql_thread_id: 46
                 trx_query: DELETE FROM t WHERE id = 10
       trx_operation_state: starting index read
         trx_tables_in_use: 1
         trx_tables_locked: 1
          trx_lock_structs: 2
     trx_lock_memory_bytes: 1136
           trx_rows_locked: 1
         trx_rows_modified: 0
   trx_concurrency_tickets: 0
       trx_isolation_level: REPEATABLE READ
         trx_unique_checks: 1
    trx_foreign_key_checks: 1
trx_last_foreign_key_error: NULL
          trx_is_read_only: 0
trx_autocommit_non_locking: 0

1.1.1.2.9.1.1.1.35 Information Schema TEMP_TABLES_INFO Table

MariaDB 10.2.2 - 10.2.3

The TEMP_TABLES_INFO table was introduced in MariaDB 10.2.2 and was removed in MariaDB 10.2.4. See MDEV-12459 progress on an alternative.

The Information Schema TEMP_TABLES_INFO table contains information about active InnoDB temporary tables. All user and system-created temporary tables are reported when querying this table, with the exception of optimized internal temporary tables. The data is stored in memory.

Previously, InnoDB temp table metadata was rather stored in InnoDB system tables.

It has the following columns:

ColumnDescription
TABLE_IDTable ID.
NAMETable name.
N_COLSNumber of columns in the temporary table, including three hidden columns that InnoDB creates (DB_ROW_ID, DB_TRX_ID, and DB_ROLL_PTR).
SPACENumerical identifier for the tablespace identifier holding the temporary table. Compressed temporary tables are stored by default in separate per-table tablespaces in the temporary file directory. For non-compressed tables, the shared temporary table is named ibtmp1, found in the data directory. Always a non-zero value, and regenerated on server restart.
PER_TABLE_TABLESPACEIf TRUE, the temporary table resides in a separate per-table tablespace. If FALSE, it resides in the shared temporary tablespace.
IS_COMPRESSEDTRUE if the table is compressed.

The PROCESS privilege is required to view the table.

Examples

CREATE TEMPORARY TABLE t (i INT) ENGINE=INNODB;

SELECT * FROM INFORMATION_SCHEMA.INNODB_TEMP_TABLE_INFO;
+----------+--------------+--------+-------+----------------------+---------------+
| TABLE_ID | NAME         | N_COLS | SPACE | PER_TABLE_TABLESPACE | IS_COMPRESSED |
+----------+--------------+--------+-------+----------------------+---------------+
|       39 | #sql1c93_3_1 |      4 |    64 | FALSE                | FALSE         |
+----------+--------------+--------+-------+----------------------+---------------+

Adding a compressed table:

SET GLOBAL innodb_file_format="Barracuda";

CREATE TEMPORARY TABLE t2 (i INT) ROW_FORMAT=COMPRESSED ENGINE=INNODB;

SELECT * FROM INFORMATION_SCHEMA.INNODB_TEMP_TABLE_INFO;
+----------+--------------+--------+-------+----------------------+---------------+
| TABLE_ID | NAME         | N_COLS | SPACE | PER_TABLE_TABLESPACE | IS_COMPRESSED |
+----------+--------------+--------+-------+----------------------+---------------+
|       40 | #sql1c93_3_3 |      4 |    65 | TRUE                 | TRUE          |
|       39 | #sql1c93_3_1 |      4 |    64 | FALSE                | FALSE         |
+----------+--------------+--------+-------+----------------------+---------------+

1.1.1.2.9.1.1.2 Information Schema MyRocks Tables

List of Information Schema tables specifically related to MyRocks.

1.1.1.2.9.1.1.2.1 Information Schema ROCKSDB_CFSTATS Table

The Information Schema ROCKSDB_CFSTATS table is included as part of the MyRocks storage engine.

The PROCESS privilege is required to view the table.

It contains the following columns:

ColumnDescription
CF_NAME
STAT_TYPE
VALUE

1.1.1.2.9.1.1.2.2 Information Schema ROCKSDB_CF_OPTIONS Table

The Information Schema ROCKSDB_CF_OPTIONS table is included as part of the MyRocks storage engine, and contains infomation about MyRocks column families.

The PROCESS privilege is required to view the table.

It contains the following columns:

ColumnDescription
CF_NAMEColumn family name.
OPTION_TYPE
VALUE

1.1.1.2.9.1.1.2.3 Information Schema ROCKSDB_COMPACTION_STATS Table

The Information Schema ROCKSDB_COMPACTION_STATS table is included as part of the MyRocks storage engine.

The PROCESS privilege is required to view the table.

It contains the following columns:

ColumnDescription
CF_NAME
LEVEL
TYPE
VALUE

1.1.1.2.9.1.1.2.4 Information Schema ROCKSDB_DBSTATS Table

The Information Schema ROCKSDB_DBSTATS table is included as part of the MyRocks storage engine.

The PROCESS privilege is required to view the table.

It contains the following columns:

ColumnDescription
STAT_TYPE
VALUE

1.1.1.2.9.1.1.2.5 Information Schema ROCKSDB_DDL Table

The Information Schema ROCKSDB_DDL table is included as part of the MyRocks storage engine.

The PROCESS privilege is required to view the table.

It contains the following columns:

ColumnDescription
TABLE_SCHEMA
TABLE_NAME
PARTITION_NAME
INDEX_NAME
COLUMN_FAMILY
INDEX_NUMBER
INDEX_TYPE
KV_FORMAT_VERSION
TTL_DURATION
INDEX_FLAGS
CF
AUTO_INCREMENT

1.1.1.2.9.1.1.2.6 Information Schema ROCKSDB_DEADLOCK Table

The Information Schema ROCKSDB_DEADLOCK table is included as part of the MyRocks storage engine.

The PROCESS privilege is required to view the table.

It contains the following columns:

ColumnDescription
DEADLOCK_ID
TIMESTAMP
TRANSACTION_ID
CF_NAME
WAITING_KEY
LOCK_TYPE
INDEX_NAME
TABLE_NAME
ROLLED_BACK

1.1.1.2.9.1.1.2.7 Information Schema ROCKSDB_GLOBAL_INFO Table

The Information Schema ROCKSDB_GLOBAL_INFO table is included as part of the MyRocks storage engine.

The PROCESS privilege is required to view the table.

It contains the following columns:

ColumnDescription
TYPE
NAME
VALUE

1.1.1.2.9.1.1.2.8 Information Schema ROCKSDB_INDEX_FILE_MAP Table

The Information Schema ROCKSDB_INDEX_FILE_MAP table is included as part of the MyRocks storage engine.

The PROCESS privilege is required to view the table.

It contains the following columns:

ColumnDescription
COLUMN_FAMILY
INDEX_NUMBER
SST_NAME
NUM_ROWS
DATA_SIZE
ENTRY_DELETES
ENTRY_SINGLEDELETES
ENTRY_MERGES
ENTRY_OTHERS
DISTINCT_KEYS_PREFIX

1.1.1.2.9.1.1.2.9 Information Schema ROCKSDB_LOCKS Table

The Information Schema ROCKSDB_LOCKS table is included as part of the MyRocks storage engine.

The PROCESS privilege is required to view the table.

It contains the following columns:

ColumnDescription
COLUMN_FAMILY_ID
TRANSACTION_ID
KEY
MODE

1.1.1.2.9.1.1.2.10 Information Schema ROCKSDB_PERF_CONTEXT Table

The Information Schema ROCKSDB_PERF_CONTEXT table is included as part of the MyRocks storage engine and includes per-table/partition counters .

The PROCESS privilege is required to view the table.

It contains the following columns:

ColumnDescription
TABLE_SCHEMA
TABLE_NAME
PARTITION_NAME
STAT_TYPE
VALUE

Note: for multi-table queries, all counter increments are "billed" to the first table in the query: https://github.com/facebook/mysql-5.6/issues/1018

1.1.1.2.9.1.1.2.11 Information Schema ROCKSDB_PERF_CONTEXT_GLOBAL Table

The Information Schema ROCKSDB_PERF_CONTEXT_GLOBAL table is included as part of the MyRocks storage engine and includes global counter information.

The PROCESS privilege is required to view the table.

It contains the following columns:

ColumnDescription
STAT_TYPE
VALUE

1.1.1.2.9.1.1.2.12 Information Schema ROCKSDB_SST_PROPS Table

The Information Schema ROCKSDB_SST_PROPS table is included as part of the MyRocks storage engine.

The PROCESS privilege is required to view the table.

It contains the following columns:

ColumnDescription
SST_NAME
COLUMN_FAMILY
DATA_BLOCKS
ENTRIES
RAW_KEY_SIZE
RAW_VALUE_SIZE
DATA_BLOCK_SIZE
INDEX_BLOCK_SIZE
INDEX_PARTITIONS
TOP_LEVEL_INDEX_SIZE
FILTER_BLOCK_SIZE
COMPRESSION_ALGO
CREATION_TIME

1.1.1.2.9.1.1.2.13 Information Schema ROCKSDB_TRX Table

The Information Schema ROCKSDB_TRX table is included as part of the MyRocks storage engine.

The PROCESS privilege is required to view the table.

It contains the following columns:

ColumnDescription
TRANSACTION_ID
STATE
NAME
WRITE_COUNT
LOCK_COUNT
TIMEOUT_SEC
WAITING_KEY
WAITING_COLUMN_FAMILY_ID
IS_REPLICATION
SKIP_TRX_API
READ_ONLY
HAS_DEADLOCK_DETECTION
NUM_ONGOING_BULKLOAD
THREAD_ID
QUERY

1.1.1.2.9.1.1.3 ColumnStore Information Schema Tables

  1. COLUMNSTORE_TABLES
  2. COLUMNSTORE_COLUMNS
  3. COLUMNSTORE_EXTENTS
  4. COLUMNSTORE_FILES
  5. Stored Procedures
    1. total_usage()
    2. table_usage()
    3. compression_ratio()

MariaDB ColumnStore has four Information Schema tables that expose information about the table and column storage. These tables were added in version 1.0.5 of ColumnStore and were heavily modified for 1.0.6.

COLUMNSTORE_TABLES

The first table is the INFORMATION_SCHEMA.COLUMNSTORE_TABLES. This contains information about the tables inside ColumnStore. The table layout is as follows:

ColumnDescription
TABLE_SCHEMAThe database schema for the table
TABLE_NAMEThe table name
OBJECT_IDThe ColumnStore object ID for the table
CREATION_DATEThe date the table was created
COLUMN_COUNTThe number of columns in the table
AUTOINCREMENTThe start autoincrement value for the table set during CREATE TABLE

Note: Tables created with ColumnStore 1.0.4 or lower will have the year field of the creation data set incorrectly by 1900 years.

COLUMNSTORE_COLUMNS

The INFORMATION_SCHEMA.COLUMNSTORE_COLUMNS table contains information about every single column inside ColumnStore. The table layout is as follows:

ColumnDescription
TABLE_SCHEMAThe database schema for the table
TABLE_NAMEThe table name for the column
COLUMN_NAMEThe column name
OBJECT_IDThe object ID for the column
DICTIONARY_OBJECT_IDThe dictionary object ID for the column (NULL if there is no dictionary object
LIST_OBJECT_IDPlaceholder for future information
TREE_OBJECT_IDPlaceholder for future information
DATA_TYPEThe data type for the column
COLUMN_LENGTHThe data length for the column
COLUMN_POSITIONThe position of the column in the table, starting at 0
COLUMN_DEFAULTThe default value for the column
IS_NULLABLEWhether or not the column can be set to NULL
NUMERIC_PRECISIONThe numeric precision for the column
NUMERIC_SCALEThe numeric scale for the column
IS_AUTOINCREMENTSet to 1 if the column is an autoincrement column
COMPRESSION_TYPEThe type of compression (either "None" or "Snappy")

COLUMNSTORE_EXTENTS

This table displays the extent map in a user consumable form. An extent is a collection of details about a section of data related to a columnstore column. A majority of columns in ColumnStore will have multiple extents and the columns table above can be joined to this one to filter results by table or column. The table layout is as follows:

ColumnDescription
OBJECT_IDThe object ID for the extent
OBJECT_TYPEWhether this is a "Column" or "Dictionary" extent
LOGICAL_BLOCK_STARTColumnStore's internal start LBID for this extent
LOGICAL_BLOCK_ENDColumnStore's internal end LBID for this extent
MIN_VALUEThis minimum value stored in this extent
MAX_VALUEThe maximum value stored in this extent
WIDTHThe data width for the extent
DBROOTThe DBRoot number for the extent
PARTITION_IDThe parition ID for the extent
SEGMENT_IDThe segment ID for the extent
BLOCK_OFFSETThe block offset for the data file, each data file can contain multiple extents for a column
MAX_BLOCKSThe maximum number of blocks for the extent
HIGH_WATER_MARKThe last block committed to the extent (starting at 0)
STATEThe state of the extent (see below)
STATUSThe availability status for the column which is either "Available", "Unavailable" or "Out of service"
DATA_SIZEThe uncompressed data size for the extent calculated as (HWM + 1) * BLOCK_SIZE

Notes:

  1. The state is "Valid" for a normal state, "Invalid" if a cpimport has completed but the table has not yet been accessed (min/max values will be invalid) or "Updating" if there is a DML statement writing to the column
  2. In ColumnStore the block size is 8192 bytes
  3. By default ColumnStore will write create an extent file of 256*1024*WIDTH bytes for the first partition, if this is too small then for uncompressed data it will create a file of the maximum size for the extent (MAX_BLOCKS * BLOCK_SIZE). Snappy always compression adds a header block.
  4. Object IDs of less than 3000 are for internal tables and will not appear in any of the information schema tables
  5. Prior to 1.0.12 / 1.1.2 DATA_SIZE was incorrectly calculated
  6. HWM is set to zero for the lower segments when there are multiple segments in an extent file, these can be observed when BLOCK_OFFSET > 0
  7. When HWM is 0 the DATA_SIZE will show 0 instead of 8192 to avoid confusion when there is multiple segments in an extent file

COLUMNSTORE_FILES

The columnstore_files table provides information about each file associated with extensions. Each extension can reuse a file at different block offsets so this is not a 1:1 relationship to the columnstore_extents table.

ColumnDescription
OBJECT_IDThe object ID for the extent
SEGMENT_IDThe segment ID for the extent
PARTITION_IDThe partition ID for the extent
FILENAMEThe full path and filename for the extent file, multiple extents for the same column can point to this file with different BLOCK_OFFSETs
FILE_SIZEThe disk file size for the extent
COMPRESSED_DATA_SIZEThe amount of the compressed file used, NULL if this is an uncompressed file

Stored Procedures

A few stored procedures were added in 1.0.6 to provide summaries based on the information schema tables. These can be accessed from the COLUMNSTORE_INFO schema.

total_usage()

The total_usage() procedure gives a total disk usage summary for all the columns in ColumnStore with the exception of the columns used for internal maintenance. It is executed using the following query:

> call columnstore_info.total_usage();

table_usage()

The table_usage() procedure gives a the total data disk usage, dictionary disk usage and grand total disk usage per-table. It can be called in several ways, the first gives a total for each table:

> call columnstore_info.table_usage(NULL, NULL);

Or for a specific table, my_table in my_schema in this example:

> call columnstore_info.table_usage('my_schema', 'my_table');

You can also request all tables for a specified schema:

> call columnstore_info.table_usage('my_schema', NULL);

Note: The quotes around the table name are required, an error will occur without them.

compression_ratio()

The compression_ratio() procedure calculates the average compression ratio across all the compressed extents in ColumnStore. It is called using:

> call columnstore_info.compression_ratio();

Note: The compression ratio is incorrectly calculated before versions 1.0.12 / 1.1.2

1.1.1.2.9.1.1.4 Information Schema ALL_PLUGINS Table

Description

The Information Schema ALL_PLUGINS table contains information about server plugins, whether installed or not.

It contains the following columns:

ColumnDescription
PLUGIN_NAMEName of the plugin.
PLUGIN_VERSIONVersion from the plugin's general type descriptor.
PLUGIN_STATUSPlugin status, one of ACTIVE, INACTIVE, DISABLED, DELETED or NOT INSTALLED.
PLUGIN_TYPEPlugin type; STORAGE ENGINE, INFORMATION_SCHEMA, AUTHENTICATION, REPLICATION, DAEMON or AUDIT.
PLUGIN_TYPE_VERSIONVersion from the plugin's type-specific descriptor.
PLUGIN_LIBRARYPlugin's shared object file name, located in the directory specified by the plugin_dir system variable, and used by the INSTALL PLUGIN and UNINSTALL PLUGIN statements. NULL if the plugin is complied in and cannot be uninstalled.
PLUGIN_LIBRARY_VERSIONVersion from the plugin's API interface.
PLUGIN_AUTHORAuthor of the plugin.
PLUGIN_DESCRIPTIONDescription.
PLUGIN_LICENSEPlugin's licence.
LOAD_OPTIONHow the plugin was loaded; one of OFF, ON, FORCE or FORCE_PLUS_PERMANENT. See Installing Plugins.
PLUGIN_MATURITYPlugin's maturity level; one of Unknown, Experimental, Alpha, Beta,'Gamma, and Stable.
PLUGIN_AUTH_VERSIONPlugin's version as determined by the plugin author. An example would be '0.99 beta 1'.

It provides a superset of the information shown by the SHOW PLUGINS SONAME statement, as well as the information_schema.PLUGINS table. For specific information about storage engines (a particular type of plugin), see the Information Schema ENGINES table and the SHOW ENGINES statement.

The table is not a standard Information Schema table, and is a MariaDB extension.

Example

SELECT * FROM information_schema.all_plugins\G
*************************** 1. row ***************************
           PLUGIN_NAME: binlog
        PLUGIN_VERSION: 1.0
         PLUGIN_STATUS: ACTIVE
           PLUGIN_TYPE: STORAGE ENGINE
   PLUGIN_TYPE_VERSION: 100314.0
        PLUGIN_LIBRARY: NULL
PLUGIN_LIBRARY_VERSION: NULL
         PLUGIN_AUTHOR: MySQL AB
    PLUGIN_DESCRIPTION: This is a pseudo storage engine to represent the binlog in a transaction
        PLUGIN_LICENSE: GPL
           LOAD_OPTION: FORCE
       PLUGIN_MATURITY: Stable
   PLUGIN_AUTH_VERSION: 1.0
*************************** 2. row ***************************
           PLUGIN_NAME: mysql_native_password
        PLUGIN_VERSION: 1.0
         PLUGIN_STATUS: ACTIVE
           PLUGIN_TYPE: AUTHENTICATION
   PLUGIN_TYPE_VERSION: 2.1
        PLUGIN_LIBRARY: NULL
PLUGIN_LIBRARY_VERSION: NULL
         PLUGIN_AUTHOR: R.J.Silk, Sergei Golubchik
    PLUGIN_DESCRIPTION: Native MySQL authentication
        PLUGIN_LICENSE: GPL
           LOAD_OPTION: FORCE
       PLUGIN_MATURITY: Stable
   PLUGIN_AUTH_VERSION: 1.0
*************************** 3. row ***************************
           PLUGIN_NAME: mysql_old_password
        PLUGIN_VERSION: 1.0
         PLUGIN_STATUS: ACTIVE
           PLUGIN_TYPE: AUTHENTICATION
   PLUGIN_TYPE_VERSION: 2.1
        PLUGIN_LIBRARY: NULL
PLUGIN_LIBRARY_VERSION: NULL
         PLUGIN_AUTHOR: R.J.Silk, Sergei Golubchik
    PLUGIN_DESCRIPTION: Old MySQL-4.0 authentication
        PLUGIN_LICENSE: GPL
           LOAD_OPTION: FORCE
       PLUGIN_MATURITY: Stable
   PLUGIN_AUTH_VERSION: 1.0
...
*************************** 104. row ***************************
           PLUGIN_NAME: WSREP_MEMBERSHIP
        PLUGIN_VERSION: 1.0
         PLUGIN_STATUS: NOT INSTALLED
           PLUGIN_TYPE: INFORMATION SCHEMA
   PLUGIN_TYPE_VERSION: 100314.0
        PLUGIN_LIBRARY: wsrep_info.so
PLUGIN_LIBRARY_VERSION: 1.13
         PLUGIN_AUTHOR: Nirbhay Choubey
    PLUGIN_DESCRIPTION: Information about group members
        PLUGIN_LICENSE: GPL
           LOAD_OPTION: OFF
       PLUGIN_MATURITY: Stable
   PLUGIN_AUTH_VERSION: 1.0
*************************** 105. row ***************************
           PLUGIN_NAME: WSREP_STATUS
        PLUGIN_VERSION: 1.0
         PLUGIN_STATUS: NOT INSTALLED
           PLUGIN_TYPE: INFORMATION SCHEMA
   PLUGIN_TYPE_VERSION: 100314.0
        PLUGIN_LIBRARY: wsrep_info.so
PLUGIN_LIBRARY_VERSION: 1.13
         PLUGIN_AUTHOR: Nirbhay Choubey
    PLUGIN_DESCRIPTION: Group view information
        PLUGIN_LICENSE: GPL
           LOAD_OPTION: OFF
       PLUGIN_MATURITY: Stable

1.1.1.2.9.1.1.5 Information Schema APPLICABLE_ROLES Table

The Information Schema APPLICABLE_ROLES table shows the role authorizations that the current user may use.

It contains the following columns:

ColumnDescriptionAdded
GRANTEEAccount that the role was granted to.
ROLE_NAMEName of the role.
IS_GRANTABLEWhether the role can be granted or not.
IS_DEFAULTWhether the role is the user's default role or notMariaDB 10.1.3

The current role is in the ENABLED_ROLES Information Schema table.

Example

SELECT * FROM information_schema.APPLICABLE_ROLES;
+----------------+-------------+--------------+------------+
| GRANTEE        | ROLE_NAME   | IS_GRANTABLE | IS_DEFAULT |
+----------------+-------------+--------------+------------+
| root@localhost | journalist  | YES          | NO         |
| root@localhost | staff       | YES          | NO         |
| root@localhost | dd          | YES          | NO         |
| root@localhost | dog         | YES          | NO         |
+----------------+-------------+--------------+------------+

1.1.1.2.9.1.1.6 Information Schema CHARACTER_SETS Table

The Information Schema CHARACTER_SETS table contains a list of supported character sets, their default collations and maximum lengths.

It contains the following columns:

ColumnDescription
CHARACTER_SET_NAMEName of the character set.
DEFAULT_COLLATE_NAMEDefault collation used.
DESCRIPTIONCharacter set description.
MAXLENMaximum length.

The SHOW CHARACTER SET statement returns the same results (although in a different order), and both can be refined in the same way. For example, the following two statements return the same results:

SHOW CHARACTER SET WHERE Maxlen LIKE '2';

and

SELECT * FROM information_schema.CHARACTER_SETS 
WHERE MAXLEN LIKE '2';

See Setting Character Sets and Collations for details on specifying the character set at the server, database, table and column levels, and Supported Character Sets and Collations for a full list of supported characters sets and collations.

Example

SELECT CHARACTER_SET_NAME FROM information_schema.CHARACTER_SETS 
WHERE DEFAULT_COLLATE_NAME LIKE '%chinese%';
+--------------------+
| CHARACTER_SET_NAME |
+--------------------+
| big5               |
| gb2312             |
| gbk                |
+--------------------+

1.1.1.2.9.1.1.7 Information Schema CHECK_CONSTRAINTS Table

MariaDB starting with 10.2.22

The Information Schema CHECK_CONSTRAINTS Table was introduced in MariaDB 10.3.10 and MariaDB 10.2.22.

The Information Schema CHECK_CONSTRAINTS table stores metadata about the constraints defined for tables in all databases.

It contains the following columns:

ColumnDescription
CONSTRAINT_CATALOGAlways contains the string 'def'.
CONSTRAINT_SCHEMADatabase name.
TABLE_NAMETable name.
CONSTRAINT_NAMEConstraint name.
MariaDB starting with 10.5.10
LEVELType of the constraint ('Column' or 'Table').
CHECK_CLAUSEConstraint clause.

Example

A table with a numeric table check constraint and with a default check constraint name:

CREATE TABLE t ( a int, CHECK (a>10));

To see check constraint call check_constraints table from information schema.

SELECT * from INFORMATION_SCHEMA.CHECK_CONSTRAINTS\G

*************************** 1. row ***************************
CONSTRAINT_CATALOG: def
 CONSTRAINT_SCHEMA: test
   CONSTRAINT_NAME: CONSTRAINT_1
        TABLE_NAME: t
      CHECK_CLAUSE: `a` > 10

A new table check constraint called a_upper:

ALTER TABLE t ADD CONSTRAINT a_upper CHECK (a<100);

SELECT * from INFORMATION_SCHEMA.CHECK_CONSTRAINTS\G

*************************** 1. row ***************************
CONSTRAINT_CATALOG: def
 CONSTRAINT_SCHEMA: test
   CONSTRAINT_NAME: CONSTRAINT_1
        TABLE_NAME: t
      CHECK_CLAUSE: `a` > 10
*************************** 2. row ***************************
CONSTRAINT_CATALOG: def
 CONSTRAINT_SCHEMA: test
   CONSTRAINT_NAME: a_upper
        TABLE_NAME: t
      CHECK_CLAUSE: `a` < 100

A new table tt with a field check constraint called b , as well as a table check constraint called b_upper:

CREATE TABLE tt(b int CHECK(b>0),CONSTRAINT b_upper CHECK(b<50));

SELECT * from INFORMATION_SCHEMA.CHECK_CONSTRAINTS;
+--------------------+-------------------+-----------------+------------+--------------+
| CONSTRAINT_CATALOG | CONSTRAINT_SCHEMA | CONSTRAINT_NAME | TABLE_NAME | CHECK_CLAUSE |
+--------------------+-------------------+-----------------+------------+--------------+
| def                | test              | b               | tt         | `b` > 0      |
| def                | test              | b_upper         | tt         | `b` < 50     |
| def                | test              | CONSTRAINT_1    | t          | `a` > 10     |
| def                | test              | a_upper         | t          | `a` < 100    |
+--------------------+-------------------+-----------------+------------+--------------+

Note: The name of the field constraint is the same as the field name.

After dropping the default table constraint called CONSTRAINT_1:

ALTER TABLE t DROP CONSTRAINT CONSTRAINT_1;

SELECT * from INFORMATION_SCHEMA.CHECK_CONSTRAINTS;
+--------------------+-------------------+-----------------+------------+--------------+
| CONSTRAINT_CATALOG | CONSTRAINT_SCHEMA | CONSTRAINT_NAME | TABLE_NAME | CHECK_CLAUSE |
+--------------------+-------------------+-----------------+------------+--------------+
| def                | test              | b               | tt         | `b` > 0      |
| def                | test              | b_upper         | tt         | `b` < 50     |
| def                | test              | a_upper         | t          | `a` < 100    |
+--------------------+-------------------+-----------------+------------+--------------+

Trying to insert invalid arguments into table t and tt generates an error.

INSERT INTO t VALUES (10),(20),(100);
ERROR 4025 (23000): CONSTRAINT `a_upper` failed for `test`.`t`

INSERT INTO tt VALUES (10),(-10),(100);
ERROR 4025 (23000): CONSTRAINT `b` failed for `test`.`tt`

INSERT INTO tt VALUES (10),(20),(100);
ERROR 4025 (23000): CONSTRAINT `b_upper` failed for `test`.`tt`

From MariaDB 10.5.10:

create table majra(check(x>0), x int, y int check(y < 0), z int,
                              constraint z check(z>0), constraint xyz check(x<10 and y<10 and z<10));
Query OK, 0 rows affected (0.036 sec)

show create table majra;
+-------+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Table | Create Table                                                                                                                                                                                                                                                                                                   |
+-------+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| majra | CREATE TABLE `majra` (
  `x` int(11) DEFAULT NULL,
  `y` int(11) DEFAULT NULL CHECK (`y` < 0),
  `z` int(11) DEFAULT NULL,
  CONSTRAINT `CONSTRAINT_1` CHECK (`x` > 0),
  CONSTRAINT `z` CHECK (`z` > 0),
  CONSTRAINT `xyz` CHECK (`x` < 10 and `y` < 10 and `z` < 10)
) ENGINE=InnoDB DEFAULT CHARSET=latin1 |
+-------+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
1 row in set (0.000 sec)


select * from information_schema.check_constraints where table_name='majra';
+--------------------+-------------------+------------+-----------------+--------+------------------------------------+
| CONSTRAINT_CATALOG | CONSTRAINT_SCHEMA | TABLE_NAME | CONSTRAINT_NAME | LEVEL  | CHECK_CLAUSE                       |
+--------------------+-------------------+------------+-----------------+--------+------------------------------------+
| def                | test              | majra      | y               | Column | `y` < 0                            |
| def                | test              | majra      | CONSTRAINT_1    | Table  | `x` > 0                            |
| def                | test              | majra      | z               | Table  | `z` > 0                            |
| def                | test              | majra      | xyz             | Table  | `x` < 10 and `y` < 10 and `z` < 10 |
+--------------------+-------------------+------------+-----------------+--------+------------------------------------+
4 rows in set (0.001 sec)

1.1.1.2.9.1.1.8 Information Schema CLIENT_STATISTICS Table

The Information Schema CLIENT_STATISTICS table holds statistics about client connections. This is part of the User Statistics feature, which is not enabled by default.

It contains the following columns:

FieldTypeNotes
CLIENTVARCHAR(64)The IP address or hostname the connection originated from.
TOTAL_CONNECTIONSINT(21)The number of connections created for this client.
CONCURRENT_CONNECTIONSINT(21)The number of concurrent connections for this client.
CONNECTED_TIMEINT(21)The cumulative number of seconds elapsed while there were connections from this client.
BUSY_TIMEDOUBLEThe cumulative number of seconds there was activity on connections from this client.
CPU_TIMEDOUBLEThe cumulative CPU time elapsed while servicing this client's connections. Note that this number may be wrong on SMP system if there was a CPU migration for the thread during the execution of the query.
BYTES_RECEIVEDINT(21)The number of bytes received from this client's connections.
BYTES_SENTINT(21)The number of bytes sent to this client's connections.
BINLOG_BYTES_WRITTENINT(21)The number of bytes written to the binary log from this client's connections.
ROWS_READINT(21)The number of rows read by this client's connections.
ROWS_SENTINT(21)The number of rows sent by this client's connections.
ROWS_DELETEDINT(21)The number of rows deleted by this client's connections.
ROWS_INSERTEDINT(21)The number of rows inserted by this client's connections.
ROWS_UPDATEDINT(21)The number of rows updated by this client's connections.
SELECT_COMMANDSINT(21)The number of SELECT commands executed from this client's connections.
UPDATE_COMMANDSINT(21)The number of UPDATE commands executed from this client's connections.
OTHER_COMMANDSINT(21)The number of other commands executed from this client's connections.
COMMIT_TRANSACTIONSINT(21)The number of COMMIT commands issued by this client's connections.
ROLLBACK_TRANSACTIONSINT(21)The number of ROLLBACK commands issued by this client's connections.
DENIED_CONNECTIONSINT(21)The number of connections denied to this client.
LOST_CONNECTIONSINT(21)The number of this client's connections that were terminated uncleanly.
ACCESS_DENIEDINT(21)The number of times this client's connections issued commands that were denied.
EMPTY_QUERIESINT(21)The number of times this client's connections sent queries that returned no results to the server.
TOTAL_SSL_CONNECTIONSINT(21)The number of TLS connections created for this client. (>= MariaDB 10.1.1)
MAX_STATEMENT_TIME_EXCEEDEDINT(21)The number of times a statement was aborted, because it was executed longer than its MAX_STATEMENT_TIME threshold. (>= MariaDB 10.1.1)

Example

SELECT * FROM information_schema.CLIENT_STATISTICS\G
*************************** 1. row ***************************
                CLIENT: localhost
     TOTAL_CONNECTIONS: 3
CONCURRENT_CONNECTIONS: 0
        CONNECTED_TIME: 4883
             BUSY_TIME: 0.009722
              CPU_TIME: 0.0102131
        BYTES_RECEIVED: 841
            BYTES_SENT: 13897
  BINLOG_BYTES_WRITTEN: 0
             ROWS_READ: 0
             ROWS_SENT: 214
          ROWS_DELETED: 0
         ROWS_INSERTED: 207
          ROWS_UPDATED: 0
       SELECT_COMMANDS: 10
       UPDATE_COMMANDS: 0
        OTHER_COMMANDS: 13
   COMMIT_TRANSACTIONS: 0
 ROLLBACK_TRANSACTIONS: 0
    DENIED_CONNECTIONS: 0
      LOST_CONNECTIONS: 0
         ACCESS_DENIED: 0
         EMPTY_QUERIES: 1

1.1.1.2.9.1.1.9 Information Schema COLLATION_CHARACTER_SET_APPLICABILITY Table

The Information Schema COLLATION_CHARACTER_SET_APPLICABILITY table shows which character sets are associated with which collations.

It contains the following columns:

ColumnDescription
COLLATION_NAMECollation name.
CHARACTER_SET_NAMEName of the associated character set.

COLLATION_CHARACTER_SET_APPLICABILITY is essentially a subset of the COLLATIONS table.

SELECT COLLATION_NAME,CHARACTER_SET_NAME FROM information_schema.COLLATIONS;

and 

SELECT * FROM information_schema.COLLATION_CHARACTER_SET_APPLICABILITY;

will return identical results.

See Setting Character Sets and Collations for details on specifying the character set at the server, database, table and column levels.

Example

SELECT * FROM information_schema.COLLATION_CHARACTER_SET_APPLICABILITY 
WHERE CHARACTER_SET_NAME='utf32';
+---------------------+--------------------+
| COLLATION_NAME      | CHARACTER_SET_NAME |
+---------------------+--------------------+
| utf32_general_ci    | utf32              |
| utf32_bin           | utf32              |
| utf32_unicode_ci    | utf32              |
| utf32_icelandic_ci  | utf32              |
| utf32_latvian_ci    | utf32              |
| utf32_romanian_ci   | utf32              |
| utf32_slovenian_ci  | utf32              |
| utf32_polish_ci     | utf32              |
| utf32_estonian_ci   | utf32              |
| utf32_spanish_ci    | utf32              |
| utf32_swedish_ci    | utf32              |
| utf32_turkish_ci    | utf32              |
| utf32_czech_ci      | utf32              |
| utf32_danish_ci     | utf32              |
| utf32_lithuanian_ci | utf32              |
| utf32_slovak_ci     | utf32              |
| utf32_spanish2_ci   | utf32              |
| utf32_roman_ci      | utf32              |
| utf32_persian_ci    | utf32              |
| utf32_esperanto_ci  | utf32              |
| utf32_hungarian_ci  | utf32              |
| utf32_sinhala_ci    | utf32              |
| utf32_german2_ci    | utf32              |
| utf32_croatian_ci   | utf32              |
+---------------------+--------------------+

1.1.1.2.9.1.1.10 Information Schema COLLATIONS Table

Contents

  1. NO PAD collations
  2. Example
  3. See Also

The Information Schema COLLATIONS table contains a list of supported collations.

It contains the following columns:

ColumnDescription
COLLATION_NAMEName of the collation.
CHARACTER_SET_NAMEAssociated character set.
IDCollation id.
IS_DEFAULTWhether the collation is the character set's default.
IS_COMPILEDWhether the collation is compiled into the server.
SORTLENSort length, used for determining the memory used to sort strings in this collation.

The SHOW COLLATION statement returns the same results and both can be reduced in a similar way.

For example, in MariaDB Server 10.6, the following two statements return the same results:

SHOW COLLATION WHERE Charset LIKE 'utf8mb3';

and

SELECT * FROM information_schema.COLLATIONS 
WHERE CHARACTER_SET_NAME LIKE 'utf8mb3';

In MariaDB Server 10.5 and before, utf8 should be specified instead of utf8mb3.

NO PAD collations

MariaDB starting with 10.2

NO PAD collations regard trailing spaces as normal characters. You can get a list of all NO PAD collations as follows:

SELECT collation_name FROM information_schema.COLLATIONS
WHERE collation_name LIKE "%nopad%";  
+------------------------------+
| collation_name               |
+------------------------------+
| big5_chinese_nopad_ci        |
| big5_nopad_bin               |
...

Example

SELECT * FROM information_schema.COLLATIONS;
+------------------------------+--------------------+------+------------+-------------+---------+
| COLLATION_NAME               | CHARACTER_SET_NAME | ID   | IS_DEFAULT | IS_COMPILED | SORTLEN |
+------------------------------+--------------------+------+------------+-------------+---------+
| big5_chinese_ci              | big5               |    1 | Yes        | Yes         |       1 |
| big5_bin                     | big5               |   84 |            | Yes         |       1 |
| big5_chinese_nopad_ci        | big5               | 1025 |            | Yes         |       1 |
| big5_nopad_bin               | big5               | 1108 |            | Yes         |       1 |
| dec8_swedish_ci              | dec8               |    3 | Yes        | Yes         |       1 |
| dec8_bin                     | dec8               |   69 |            | Yes         |       1 |
| dec8_swedish_nopad_ci        | dec8               | 1027 |            | Yes         |       1 |
| dec8_nopad_bin               | dec8               | 1093 |            | Yes         |       1 |
| cp850_general_ci             | cp850              |    4 | Yes        | Yes         |       1 |
| cp850_bin                    | cp850              |   80 |            | Yes         |       1 |
...

See Also

1.1.1.2.9.1.1.11 Information Schema COLUMN_PRIVILEGES Table

The Information Schema COLUMN_PRIVILEGES table contains column privilege information derived from the mysql.columns_priv grant table.

It has the following columns:

ColumnDescription
GRANTEEIn the format user_name@host_name.
TABLE_CATALOGAlways def.
TABLE_SCHEMADatabase name.
TABLE_NAMETable name.
COLUMN_NAMEColumn name.
PRIVILEGE_TYPEOne of SELECT, INSERT, UPDATE or REFERENCES.
IS_GRANTABLEWhether the user has the GRANT OPTION for this privilege.

Similar information can be accessed with the SHOW FULL COLUMNS and SHOW GRANTS statements. See the GRANT article for more about privileges.

This information is also stored in the columns_priv table, in the mysql system database.

For a description of the privileges that are shown in this table, see column privileges.

Example

In the following example, no column-level privilege has been explicitly assigned:

SELECT * FROM information_schema.COLUMN_PRIVILEGES;
Empty set

1.1.1.2.9.1.1.12 Information Schema COLUMNS Table

The Information Schema COLUMNS table provides information about columns in each table on the server.

It contains the following columns:

ColumnDescriptionIntroduced
TABLE_CATALOGAlways contains the string 'def'.
TABLE_SCHEMADatabase name.
TABLE_NAMETable name.
COLUMN_NAMEColumn name.
ORDINAL_POSITIONColumn position in the table. Can be used for ordering.
COLUMN_DEFAULTDefault value for the column. From MariaDB 10.2.7, literals are quoted to distinguish them from expressions. NULL means that the column has no default. In MariaDB 10.2.6 and earlier, no quotes were used for any type of default and NULL can either mean that there is no default, or that the default column value is NULL.
IS_NULLABLEWhether the column can contain NULLs.
DATA_TYPEThe column's data type.
CHARACTER_MAXIMUM_LENGTHMaximum length.
CHARACTER_OCTET_LENGTHSame as the CHARACTER_MAXIMUM_LENGTH except for multi-byte character sets.
NUMERIC_PRECISIONFor numeric types, the precision (number of significant digits) for the column. NULL if not a numeric field.
NUMERIC_SCALEFor numeric types, the scale (significant digits to the right of the decimal point). NULL if not a numeric field.
DATETIME_PRECISIONFractional-seconds precision, or NULL if not a time data type.
CHARACTER_SET_NAMECharacter set if a non-binary string data type, otherwise NULL.
COLLATION_NAMECollation if a non-binary string data type, otherwise NULL.
COLUMN_TYPEColumn definition, a MySQL and MariaDB extension.
COLUMN_KEYIndex type. PRI for primary key, UNI for unique index, MUL for multiple index. A MySQL and MariaDB extension.
EXTRAAdditional information about a column, for example whether the column is an invisible column, or, from MariaDB 10.3.6, WITHOUT SYSTEM VERSIONING if the table is not a system-versioned table. A MySQL and MariaDB extension.
PRIVILEGESWhich privileges you have for the column. A MySQL and MariaDB extension.
COLUMN_COMMENTColumn comments.
IS_GENERATEDIndicates whether the column value is generated (virtual, or computed). Can be ALWAYS or NEVER.MariaDB 10.2.5
GENERATION_EXPRESSIONThe expression used for computing the column value in a generated (virtual, or computed) column.MariaDB 10.2.5

It provides information similar to, but more complete, than SHOW COLUMNS and mysqlshow.

Examples

SELECT * FROM information_schema.COLUMNS\G
...
*************************** 9. row ***************************
           TABLE_CATALOG: def
            TABLE_SCHEMA: test
              TABLE_NAME: t2
             COLUMN_NAME: j
        ORDINAL_POSITION: 1
          COLUMN_DEFAULT: NULL
             IS_NULLABLE: YES
               DATA_TYPE: longtext
CHARACTER_MAXIMUM_LENGTH: 4294967295
  CHARACTER_OCTET_LENGTH: 4294967295
       NUMERIC_PRECISION: NULL
           NUMERIC_SCALE: NULL
      DATETIME_PRECISION: NULL
      CHARACTER_SET_NAME: utf8mb4
          COLLATION_NAME: utf8mb4_bin
             COLUMN_TYPE: longtext
              COLUMN_KEY: 
                   EXTRA: 
              PRIVILEGES: select,insert,update,references
          COLUMN_COMMENT: 
            IS_GENERATED: NEVER
   GENERATION_EXPRESSION: NULL
...

CREATE TABLE t (
  s1 VARCHAR(20) DEFAULT 'ABC',
  s2 VARCHAR(20) DEFAULT (concat('A','B')),
  s3 VARCHAR(20) DEFAULT ("concat('A','B')"),
  s4 VARCHAR(20),
  s5 VARCHAR(20) DEFAULT NULL,
  s6 VARCHAR(20) NOT NULL,
  s7 VARCHAR(20) DEFAULT 'NULL' NULL,
  s8 VARCHAR(20) DEFAULT 'NULL' NOT NULL
);

SELECT 
  table_name, 
  column_name, 
  ordinal_position, 
  column_default,
  column_default IS NULL
FROM information_schema.COLUMNS
WHERE table_schema=DATABASE()
AND TABLE_NAME='t';

From MariaDB 10.2.7:

+------------+-------------+------------------+-----------------------+------------------------+
| table_name | column_name | ordinal_position | column_default        | column_default IS NULL |
+------------+-------------+------------------+-----------------------+------------------------+
| t          | s1          |                1 | 'ABC'                 |                      0 |
| t          | s2          |                2 | concat('A','B')       |                      0 |
| t          | s3          |                3 | 'concat(''A'',''B'')' |                      0 |
| t          | s4          |                4 | NULL                  |                      0 |
| t          | s5          |                5 | NULL                  |                      0 |
| t          | s6          |                6 | NULL                  |                      1 |
| t          | s7          |                7 | 'NULL'                |                      0 |
| t          | s8          |                8 | 'NULL'                |                      0 |
+------------+-------------+------------------+-----------------------+------------------------+

In the results above, the two single quotes in concat(''A'',''B'') indicate an escaped single quote - see string-literals. Note that while mysql-command-line-client appears to show the same default value for columns s5 and s6, the first is a 4-character string "NULL", while the second is the SQL NULL value.

MariaDB 10.2.6 and before:

+------------+-------------+------------------+-----------------+------------------------+
| table_name | column_name | ordinal_position | column_default  | column_default IS NULL |
+------------+-------------+------------------+-----------------+------------------------+
| t          | s1          |                1 | ABC             |                      0 |
| t          | s2          |                2 | concat('A','B') |                      0 |
| t          | s3          |                3 | concat('A','B') |                      0 |
| t          | s4          |                4 | NULL            |                      1 |
| t          | s5          |                5 | NULL            |                      1 |
| t          | s6          |                6 | NULL            |                      1 |
| t          | s7          |                7 | NULL            |                      0 |
| t          | s8          |                8 | NULL            |                      0 |
+------------+-------------+------------------+-----------------+------------------------+

1.1.1.2.9.1.1.13 Information Schema DISKS Table

MariaDB 10.1.32

The DISKS table was introduced in MariaDB 10.1.32, MariaDB 10.2.14, and MariaDB 10.3.6 as part of the DISKS plugin.

Contents

  1. Description
  2. Example
  3. See Also

Description

The DISKS table is created when the DISKS plugin is enabled, and shows metadata about disks on the system.

Before MariaDB 10.4.7, MariaDB 10.3.17, MariaDB 10.2.26 and MariaDB 10.1.41, this plugin did not check user privileges. When it is enabled, any user can query the INFORMATION_SCHEMA.DISKS table and see all the information it provides.

Since MariaDB 10.4.7, MariaDB 10.3.17, MariaDB 10.2.26 and MariaDB 10.1.41, it requires the FILE privilege.

The plugin only works on Linux.

The table contains the following columns:

ColumnDescription
DISKName of the disk itself.
PATHMount point of the disk.
TOTALTotal space in KiB.
USEDUsed amount of space in KiB.
AVAILABLEAmount of space in KiB available to non-root users.

Note that as the amount of space available to root (OS user) may be more that what is available to non-root users, 'available' + 'used' may be less than 'total'.

All paths to which a particular disk has been mounted are reported. The rationale is that someone might want to take different action e.g. depending on which disk is relevant for a particular path. This leads to the same disk being reported multiple times.

Example

SELECT * FROM information_schema.DISKS;

+-----------+-------+----------+---------+-----------+
| Disk      | Path  | Total    | Used    | Available |
+-----------+-------+----------+---------+-----------+
| /dev/vda1 | /     | 26203116 | 2178424 |  24024692 |
| /dev/vda1 | /boot | 26203116 | 2178424 |  24024692 |
| /dev/vda1 | /etc  | 26203116 | 2178424 |  24024692 |
+-----------+-------+----------+---------+-----------+

See Also

1.1.1.2.9.1.1.14 Information Schema ENABLED_ROLES Table

The Information Schema ENABLED_ROLES table shows the enabled roles for the current session.

It contains the following column:

ColumnDescription
ROLE_NAMEThe enabled role name, or NULL.

This table lists all roles that are currently enabled, one role per row — the current role, roles granted to the current role, roles granted to these roles and so on. If no role is set, the row contains a NULL value.

The roles that the current user can enable are listed in the APPLICABLE_ROLES Information Schema table.

See also CURRENT_ROLE().

Examples

SELECT * FROM information_schema.ENABLED_ROLES;
+-----------+
| ROLE_NAME |
+-----------+
| NULL      |
+-----------+

SET ROLE staff;

SELECT * FROM information_schema.ENABLED_ROLES;
+-----------+
| ROLE_NAME |
+-----------+
| staff     |
+-----------+

1.1.1.2.9.1.1.15 Information Schema ENGINES Table

The Information Schema ENGINES table displays status information about the server's storage engines.

It contains the following columns:

ColumnDescription
ENGINEName of the storage engine.
SUPPORTWhether the engine is the default, or is supported or not.
COMMENTStorage engine comments.
TRANSACTIONSWhether or not the engine supports transactions.
XAWhether or not the engine supports XA transactions.
SAVEPOINTSWhether or not savepoints are supported.

It provides identical information to the SHOW ENGINES statement. Since storage engines are plugins, different information about them is also shown in the information_schema.PLUGINS table and by the SHOW PLUGINS statement.

The table is not a standard Information Schema table, and is a MySQL and MariaDB extension.

Note that both MySQL's InnoDB and Percona's XtraDB replacement are labeled as InnoDB. However, if XtraDB is in use, it will be specified in the COMMENT field. See XtraDB and InnoDB. The same applies to FederatedX.

Example

SELECT * FROM information_schema.ENGINES\G;
*************************** 1. row ***************************
      ENGINE: InnoDB
     SUPPORT: DEFAULT
     COMMENT: Supports transactions, row-level locking, and foreign keys
TRANSACTIONS: YES
          XA: YES
  SAVEPOINTS: YES
*************************** 2. row ***************************
      ENGINE: CSV
     SUPPORT: YES
     COMMENT: CSV storage engine
TRANSACTIONS: NO
          XA: NO
  SAVEPOINTS: NO
*************************** 3. row ***************************
      ENGINE: MyISAM
     SUPPORT: YES
     COMMENT: MyISAM storage engine
TRANSACTIONS: NO
          XA: NO
  SAVEPOINTS: NO
*************************** 4. row ***************************
      ENGINE: BLACKHOLE
     SUPPORT: YES
     COMMENT: /dev/null storage engine (anything you write to it disappears)
TRANSACTIONS: NO
          XA: NO
  SAVEPOINTS: NO
*************************** 5. row ***************************
      ENGINE: FEDERATED
     SUPPORT: YES
     COMMENT: FederatedX pluggable storage engine
TRANSACTIONS: YES
          XA: NO
  SAVEPOINTS: YES
*************************** 6. row ***************************
      ENGINE: MRG_MyISAM
     SUPPORT: YES
     COMMENT: Collection of identical MyISAM tables
TRANSACTIONS: NO
          XA: NO
  SAVEPOINTS: NO
*************************** 7. row ***************************
      ENGINE: ARCHIVE
     SUPPORT: YES
     COMMENT: Archive storage engine
TRANSACTIONS: NO
          XA: NO
  SAVEPOINTS: NO
*************************** 8. row ***************************
      ENGINE: MEMORY
     SUPPORT: YES
     COMMENT: Hash based, stored in memory, useful for temporary tables
TRANSACTIONS: NO
          XA: NO
  SAVEPOINTS: NO
*************************** 9. row ***************************
      ENGINE: PERFORMANCE_SCHEMA
     SUPPORT: YES
     COMMENT: Performance Schema
TRANSACTIONS: NO
          XA: NO
  SAVEPOINTS: NO
*************************** 10. row ***************************
      ENGINE: Aria
     SUPPORT: YES
     COMMENT: Crash-safe tables with MyISAM heritage
TRANSACTIONS: NO
          XA: NO
  SAVEPOINTS: NO
10 rows in set (0.00 sec)

Check if a given storage engine is available:

SELECT SUPPORT FROM information_schema.ENGINES WHERE ENGINE LIKE 'tokudb';
Empty set

Check which storage engine supports XA transactions:

SELECT ENGINE FROM information_schema.ENGINES WHERE XA = 'YES';
+--------+
| ENGINE |
+--------+
| InnoDB |
+--------+

1.1.1.2.9.1.1.16 Information Schema EVENTS Table

The Information Schema EVENTS table stores information about Events on the server.

It contains the following columns:

ColumnDescription
EVENT_CATALOGAlways def.
EVENT_SCHEMADatabase where the event was defined.
EVENT_NAMEEvent name.
DEFINEREvent definer.
TIME_ZONETime zone used for the event's scheduling and execution, by default SYSTEM.
EVENT_BODYSQL.
EVENT_DEFINITIONThe SQL defining the event.
EVENT_TYPEEither ONE TIME or RECURRING.
EXECUTE_ATDATETIME when the event is set to execute, or NULL if recurring.
INTERVAL_VALUENumeric interval between event executions for a recurring event, or NULL if not recurring.
INTERVAL_FIELDInterval unit (e.g., HOUR)
SQL_MODEThe SQL_MODE at the time the event was created.
STARTSStart DATETIME for a recurring event, NULL if not defined or not recurring.
ENDSEnd DATETIME for a recurring event, NULL if not defined or not recurring.
STATUSOne of ENABLED, DISABLED or /SLAVESIDE_DISABLED.
ON_COMPLETIONThe ON COMPLETION clause, either PRESERVE or NOT PRESERVE .
CREATEDWhen the event was created.
LAST_ALTEREDWhen the event was last changed.
LAST_EXECUTEDWhen the event was last run.
EVENT_COMMENTThe comment provided in the CREATE EVENT statement, or an empty string if none.
ORIGINATORMariaDB server ID on which the event was created.
CHARACTER_SET_CLIENTcharacter_set_client system variable session value at the time the event was created.
COLLATION_CONNECTIONcollation_connection system variable session value at the time the event was created.
DATABASE_COLLATIONDatabase collation with which the event is linked.

The SHOW EVENTS and SHOW CREATE EVENT statements provide similar information.

1.1.1.2.9.1.1.17 Information Schema FEEDBACK Table

The Information Schema FEEDBACK table is created when the Feedback Plugin is enabled, and contains the complete contents submitted by the plugin.

It contains two columns:

ColumnDescription
VARIABLE_NAMEName of the item of information being collected.
VARIABLE_VALUEContents of the item of information being collected.

It is possible to disable automatic collection, by setting the feedback_url variable to an empty string, and to submit the contents manually, as follows:

$ mysql -e 'SELECT * FROM information_schema.FEEDBACK' > report.txt

Then you can send it by opening https://mariadb.org/feedback_plugin/post in your browser, and uploading your generated report.txt. Or you can do it from the command line with (for example):

$ curl -F data=@report.txt https://mariadb.org/feedback_plugin/post

Manual uploading allows you to be absolutely sure that we receive only the data shown in the information_schema.FEEDBACK table and that no private or sensitive information is being sent.

Example

SELECT * FROM information_schema.FEEDBACK\G
...
*************************** 906. row ***************************
 VARIABLE_NAME: Uname_sysname
VARIABLE_VALUE: Linux
*************************** 907. row ***************************
 VARIABLE_NAME: Uname_release
VARIABLE_VALUE: 3.13.0-53-generic
*************************** 908. row ***************************
 VARIABLE_NAME: Uname_version
VARIABLE_VALUE: #89-Ubuntu SMP Wed May 20 10:34:39 UTC 2015
*************************** 909. row ***************************
 VARIABLE_NAME: Uname_machine
VARIABLE_VALUE: x86_64
*************************** 910. row ***************************
 VARIABLE_NAME: Uname_distribution
VARIABLE_VALUE: lsb: Ubuntu 14.04.2 LTS
*************************** 911. row ***************************
 VARIABLE_NAME: Collation used latin1_german1_ci
VARIABLE_VALUE: 1
*************************** 912. row ***************************
 VARIABLE_NAME: Collation used latin1_swedish_ci
VARIABLE_VALUE: 18
*************************** 913. row ***************************
 VARIABLE_NAME: Collation used utf8_general_ci
VARIABLE_VALUE: 567
*************************** 914. row ***************************
 VARIABLE_NAME: Collation used latin1_bin
VARIABLE_VALUE: 1
*************************** 915. row ***************************
 VARIABLE_NAME: Collation used binary
VARIABLE_VALUE: 16
*************************** 916. row ***************************
 VARIABLE_NAME: Collation used utf8_bin
VARIABLE_VALUE: 4044

1.1.1.2.9.1.1.18 Information Schema FILES Table

The FILES tables is unused in MariaDB. See MDEV-11426.

1.1.1.2.9.1.1.19 Information Schema GEOMETRY_COLUMNS Table

Description

The Information Schema GEOMETRY_COLUMNS table provides support for Spatial Reference systems for GIS data.

It contains the following columns:

ColumnTypeNullDescription
F_TABLE_CATALOGVARCHAR(512)NOTogether with F_TABLE_SCHEMA and F_TABLE_NAME, the fully qualified name of the featured table containing the geometry column.
F_TABLE_SCHEMAVARCHAR(64)NOTogether with F_TABLE_CATALOG and F_TABLE_NAME, the fully qualified name of the featured table containing the geometry column.
F_TABLE_NAMEVARCHAR(64)NOTogether with F_TABLE_CATALOG and F_TABLE_SCHEMA, the fully qualified name of the featured table containing the geometry column.
F_GEOMETRY_COLUMNVARCHAR(64)NOName of the column in the featured table that is the geometry golumn.
G_TABLE_CATALOGVARCHAR(512)NO
G_TABLE_SCHEMAVARCHAR(64)NODatabase name of the table implementing the geometry column.
G_TABLE_NAMEVARCHAR(64)NOTable name that is implementing the geometry column.
G_GEOMETRY_COLUMNVARCHAR(64)NO
STORAGE_TYPETINYINT(2)NOBinary geometry implementation. Always 1 in MariaDB.
GEOMETRY_TYPEINT(7)NOInteger reflecting the type of geometry stored in this column (see table below).
COORD_DIMENSIONTINYINT(2)NONumber of dimensions in the spatial reference system. Always 2 in MariaDB.
MAX_PPRTINYINT(2)NOAlways 0 in MariaDB.
SRIDSMALLINT(5)NOID of the Spatial Reference System used for the coordinate geometry in this table. It is a foreign key reference to the SPATIAL_REF_SYS table.

Storage_type

The integers in the storage_type field match the geometry types as follows:

IntegerType
0GEOMETRY
1POINT
3LINESTRING
5POLYGON
7MULTIPOINT
9MULTILINESTRING
11MULTIPOLYGON

Example

CREATE TABLE g1(g GEOMETRY(9,4) REF_SYSTEM_ID=101);

SELECT * FROM information_schema.GEOMETRY_COLUMNS\G
*************************** 1. row ***************************
  F_TABLE_CATALOG: def
   F_TABLE_SCHEMA: test
     F_TABLE_NAME: g1
F_GEOMETRY_COLUMN: 
  G_TABLE_CATALOG: def
   G_TABLE_SCHEMA: test
     G_TABLE_NAME: g1
G_GEOMETRY_COLUMN: g
     STORAGE_TYPE: 1
    GEOMETRY_TYPE: 0
  COORD_DIMENSION: 2
          MAX_PPR: 0
             SRID: 101

See also

1.1.1.2.9.1.1.20 Information Schema GLOBAL_STATUS and SESSION_STATUS Tables

The Information Schema GLOBAL_STATUS and SESSION_STATUS tables store a record of all status variables and their global and session values respectively. This is the same information as displayed by the SHOW STATUS commands SHOW GLOBAL STATUS and SHOW SESSION STATUS.

They contain the following columns:

ColumnDescription
VARIABLE_NAMEStatus variable name.
VARIABLE_VALUEGlobal or session value.

Example

SELECT * FROM information_schema.GLOBAL_STATUS;
+-----------------------------------------------+--------------------+
| VARIABLE_NAME                                 | VARIABLE_VALUE     |
+-----------------------------------------------+--------------------+
...
| BINLOG_SNAPSHOT_FILE                          | mariadb-bin.000208 |
| BINLOG_SNAPSHOT_POSITION                      | 369                |
...
| THREADS_CONNECTED                             | 1                  |
| THREADS_CREATED                               | 1                  |
| THREADS_RUNNING                               | 1                  |
| UPTIME                                        | 57358              |
| UPTIME_SINCE_FLUSH_STATUS                     | 57358              |
+-----------------------------------------------+--------------------+

1.1.1.2.9.1.1.21 Information Schema GLOBAL_VARIABLES and SESSION_VARIABLES Tables

The Information Schema GLOBAL_VARIABLES and SESSION_VARIABLES tables stores a record of all system variables and their global and session values respectively. This is the same information as displayed by the SHOW VARIABLES commands SHOW GLOBAL VARIABLES and SHOW SESSION VARIABLES.

It contains the following columns:

ColumnDescription
VARIABLE_NAMESystem variable name.
VARIABLE_VALUEGlobal or session value.

Example

SELECT * FROM information_schema.GLOBAL_VARIABLES ORDER BY VARIABLE_NAME\G
*************************** 1. row *****************************
 VARIABLE_NAME: ARIA_BLOCK_SIZE
VARIABLE_VALUE: 8192
*************************** 2. row *****************************
 VARIABLE_NAME: ARIA_CHECKPOINT_LOG_ACTIVITY
VARIABLE_VALUE: 1048576
*************************** 3. row *****************************
 VARIABLE_NAME: ARIA_CHECKPOINT_INTERVAL
VARIABLE_VALUE: 30
...
*************************** 455. row ***************************
 VARIABLE_NAME: VERSION_COMPILE_MACHINE
VARIABLE_VALUE: x86_64
*************************** 456. row ***************************
 VARIABLE_NAME: VERSION_COMPILE_OS
VARIABLE_VALUE: debian-linux-gnu
*************************** 457. row ***************************
 VARIABLE_NAME: WAIT_TIMEOUT
VARIABLE_VALUE: 600

1.1.1.2.9.1.1.22 Information Schema INDEX_STATISTICS Table

The Information Schema INDEX_STATISTICS table shows statistics on index usage and makes it possible to do such things as locating unused indexes and generating the commands to remove them.

This is part of the User Statistics feature, which is not enabled by default.

It contains the following columns:

FieldTypeNotes
TABLE_SCHEMAVARCHAR(192)The schema (database) name.
TABLE_NAMEVARCHAR(192)The table name.
INDEX_NAMEVARCHAR(192)The index name (as visible in SHOW CREATE TABLE).
ROWS_READINT(21)The number of rows read from this index.

Example

SELECT * FROM information_schema.INDEX_STATISTICS 
WHERE TABLE_NAME = "author";
+--------------+------------+------------+-----------+
| TABLE_SCHEMA | TABLE_NAME | INDEX_NAME | ROWS_READ |
+--------------+------------+------------+-----------+
| books        | author     | by_name    |        15 |
+--------------+------------+------------+-----------+

1.1.1.2.9.1.1.23 Information Schema KEY_CACHES Table

The Information Schema KEY_CACHES table shows statistics about the segmented key cache,.

It contains the following columns:

Column NameDescription
KEY_CACHE_NAMEThe name of the key cache
SEGMENTStotal number of segments (set to NULL for regular key caches)
SEGMENT_NUMBERsegment number (set to NULL for any regular key caches and for rows containing aggregation statistics for segmented key caches)
FULL_SIZEmemory for cache buffers/auxiliary structures
BLOCK_SIZEsize of the blocks
USED_BLOCKSnumber of currently used blocks
UNUSED_BLOCKSnumber of currently unused blocks
DIRTY_BLOCKSnumber of currently dirty blocks
READ_REQUESTSnumber of read requests
READSnumber of actual reads from files into buffers
WRITE_REQUESTSnumber of write requests
WRITESnumber of actual writes from buffers into files

Example

SELECT * FROM information_schema.KEY_CACHES \G
********************** 1. row **********************
KEY_CACHE_NAME: default
SEGMENTS: NULL
SEGMENT_NUMBER: NULL
     FULL_SIZE: 134217728
    BLOCK_SIZE: 1024
   USED_BLOCKS: 36
 UNUSED_BLOCKS: 107146
  DIRTY_BLOCKS: 0
 READ_REQUESTS: 40305
         READS: 21
WRITE_REQUESTS: 19239
        WRITES: 358

1.1.1.2.9.1.1.24 Information Schema KEY_COLUMN_USAGE Table

The Information Schema KEY_COLUMN_USAGE table shows which key columns have constraints.

It contains the following columns:

ColumnDescription
CONSTRAINT_CATALOGAlways def.
CONSTRAINT_SCHEMADatabase name of the constraint.
CONSTRAINT_NAMEName of the constraint (PRIMARY for the primary key).
TABLE_CATALOGAlways #def.
TABLE_SCHEMADatabase name of the column constraint.
TABLE_NAMETable name of the column constraint.
COLUMN_NAMEColumn name of the constraint.
ORDINAL_POSITIONPosition of the column within the constraint.
POSITION_IN_UNIQUE_CONSTRAINTFor foreign keys, the position in the unique constraint.
REFERENCED_TABLE_SCHEMAFor foreign keys, the referenced database name.
REFERENCED_TABLE_NAMEFor foreign keys, the referenced table name.
REFERENCED_COLUMN_NAMEFor foreign keys, the referenced column name.

Example

SELECT * FROM information_schema.KEY_COLUMN_USAGE LIMIT 1 \G
********************** 1. row **********************
           CONSTRAINT_CATALOG: def
            CONSTRAINT_SCHEMA: my_website
              CONSTRAINT_NAME: PRIMARY
                TABLE_CATALOG: def
                 TABLE_SCHEMA: users
                  COLUMN_NAME: user_id
             ORDINAL_POSITION: 1
POSITION_IN_UNIQUE_CONSTRAINT: NULL
      REFERENCED_TABLE_SCHEMA: NULL
        REFERENCED_TABLE_NAME: NULL
       REFERENCED_COLUMN_NAME: NULL

See Also

1.1.1.2.9.1.1.25 Information Schema KEYWORDS Table

MariaDB starting with 10.6.3

The KEYWORDS table was added in MariaDB 10.6.3.

Description

The Information Schema KEYWORDS table contains the list of MariaDB keywords.

It contains a single column:

ColumnDescription
WORDKeyword

The table is not a standard Information Schema table, and is a MariaDB extension.

Example

SELECT * FROM INFORMATION_SCHEMA.KEYWORDS;
+-------------------------------+
| WORD                          |
+-------------------------------+
| &&                            |
| <=                            |
| <>                            |
| !=                            |
| >=                            |
| <<                            |
| >>                            |
| <=>                           |
| ACCESSIBLE                    |
| ACCOUNT                       |
| ACTION                        |
| ADD                           |
| ADMIN                         |
| AFTER                         |
| AGAINST                       |
| AGGREGATE                     |
| ALL                           |
| ALGORITHM                     |
| ALTER                         |
| ALWAYS                        |
| ANALYZE                       |
| AND                           |
| ANY                           |
| AS                            |
| ASC                           |
| ASCII                         |
| ASENSITIVE                    |
| AT                            |
| ATOMIC                        |
| AUTHORS                       |
| AUTO_INCREMENT                |
| AUTOEXTEND_SIZE               |
| AUTO                          |
| AVG                           |
| AVG_ROW_LENGTH                |
| BACKUP                        |
| BEFORE                        |
| BEGIN                         |
| BETWEEN                       |
| BIGINT                        |
| BINARY                        |
| BINLOG                        |
| BIT                           |
| BLOB                          |
| BLOCK                         |
| BODY                          |
| BOOL                          |
| BOOLEAN                       |
| BOTH                          |
| BTREE                         |
| BY                            |
| BYTE                          |
| CACHE                         |
| CALL                          |
| CASCADE                       |
| CASCADED                      |
| CASE                          |
| CATALOG_NAME                  |
| CHAIN                         |
| CHANGE                        |
| CHANGED                       |
| CHAR                          |
| CHARACTER                     |
| CHARSET                       |
| CHECK                         |
| CHECKPOINT                    |
| CHECKSUM                      |
| CIPHER                        |
| CLASS_ORIGIN                  |
| CLIENT                        |
| CLOB                          |
| CLOSE                         |
| COALESCE                      |
| CODE                          |
| COLLATE                       |
| COLLATION                     |
| COLUMN                        |
| COLUMN_NAME                   |
| COLUMNS                       |
| COLUMN_ADD                    |
| COLUMN_CHECK                  |
| COLUMN_CREATE                 |
| COLUMN_DELETE                 |
| COLUMN_GET                    |
| COMMENT                       |
| COMMIT                        |
| COMMITTED                     |
| COMPACT                       |
| COMPLETION                    |
| COMPRESSED                    |
| CONCURRENT                    |
| CONDITION                     |
| CONNECTION                    |
| CONSISTENT                    |
| CONSTRAINT                    |
| CONSTRAINT_CATALOG            |
| CONSTRAINT_NAME               |
| CONSTRAINT_SCHEMA             |
| CONTAINS                      |
| CONTEXT                       |
| CONTINUE                      |
| CONTRIBUTORS                  |
| CONVERT                       |
| CPU                           |
| CREATE                        |
| CROSS                         |
| CUBE                          |
| CURRENT                       |
| CURRENT_DATE                  |
| CURRENT_POS                   |
| CURRENT_ROLE                  |
| CURRENT_TIME                  |
| CURRENT_TIMESTAMP             |
| CURRENT_USER                  |
| CURSOR                        |
| CURSOR_NAME                   |
| CYCLE                         |
| DATA                          |
| DATABASE                      |
| DATABASES                     |
| DATAFILE                      |
| DATE                          |
| DATETIME                      |
| DAY                           |
| DAY_HOUR                      |
| DAY_MICROSECOND               |
| DAY_MINUTE                    |
| DAY_SECOND                    |
| DEALLOCATE                    |
| DEC                           |
| DECIMAL                       |
| DECLARE                       |
| DEFAULT                       |
| DEFINER                       |
| DELAYED                       |
| DELAY_KEY_WRITE               |
| DELETE                        |
| DELETE_DOMAIN_ID              |
| DESC                          |
| DESCRIBE                      |
| DES_KEY_FILE                  |
| DETERMINISTIC                 |
| DIAGNOSTICS                   |
| DIRECTORY                     |
| DISABLE                       |
| DISCARD                       |
| DISK                          |
| DISTINCT                      |
| DISTINCTROW                   |
| DIV                           |
| DO                            |
| DOUBLE                        |
| DO_DOMAIN_IDS                 |
| DROP                          |
| DUAL                          |
| DUMPFILE                      |
| DUPLICATE                     |
| DYNAMIC                       |
| EACH                          |
| ELSE                          |
| ELSEIF                        |
| ELSIF                         |
| EMPTY                         |
| ENABLE                        |
| ENCLOSED                      |
| END                           |
| ENDS                          |
| ENGINE                        |
| ENGINES                       |
| ENUM                          |
| ERROR                         |
| ERRORS                        |
| ESCAPE                        |
| ESCAPED                       |
| EVENT                         |
| EVENTS                        |
| EVERY                         |
| EXAMINED                      |
| EXCEPT                        |
| EXCHANGE                      |
| EXCLUDE                       |
| EXECUTE                       |
| EXCEPTION                     |
| EXISTS                        |
| EXIT                          |
| EXPANSION                     |
| EXPIRE                        |
| EXPORT                        |
| EXPLAIN                       |
| EXTENDED                      |
| EXTENT_SIZE                   |
| FALSE                         |
| FAST                          |
| FAULTS                        |
| FEDERATED                     |
| FETCH                         |
| FIELDS                        |
| FILE                          |
| FIRST                         |
| FIXED                         |
| FLOAT                         |
| FLOAT4                        |
| FLOAT8                        |
| FLUSH                         |
| FOLLOWING                     |
| FOLLOWS                       |
| FOR                           |
| FORCE                         |
| FOREIGN                       |
| FORMAT                        |
| FOUND                         |
| FROM                          |
| FULL                          |
| FULLTEXT                      |
| FUNCTION                      |
| GENERAL                       |
| GENERATED                     |
| GET_FORMAT                    |
| GET                           |
| GLOBAL                        |
| GOTO                          |
| GRANT                         |
| GRANTS                        |
| GROUP                         |
| HANDLER                       |
| HARD                          |
| HASH                          |
| HAVING                        |
| HELP                          |
| HIGH_PRIORITY                 |
| HISTORY                       |
| HOST                          |
| HOSTS                         |
| HOUR                          |
| HOUR_MICROSECOND              |
| HOUR_MINUTE                   |
| HOUR_SECOND                   |
| ID                            |
| IDENTIFIED                    |
| IF                            |
| IGNORE                        |
| IGNORED                       |
| IGNORE_DOMAIN_IDS             |
| IGNORE_SERVER_IDS             |
| IMMEDIATE                     |
| IMPORT                        |
| INTERSECT                     |
| IN                            |
| INCREMENT                     |
| INDEX                         |
| INDEXES                       |
| INFILE                        |
| INITIAL_SIZE                  |
| INNER                         |
| INOUT                         |
| INSENSITIVE                   |
| INSERT                        |
| INSERT_METHOD                 |
| INSTALL                       |
| INT                           |
| INT1                          |
| INT2                          |
| INT3                          |
| INT4                          |
| INT8                          |
| INTEGER                       |
| INTERVAL                      |
| INVISIBLE                     |
| INTO                          |
| IO                            |
| IO_THREAD                     |
| IPC                           |
| IS                            |
| ISOLATION                     |
| ISOPEN                        |
| ISSUER                        |
| ITERATE                       |
| INVOKER                       |
| JOIN                          |
| JSON                          |
| JSON_TABLE                    |
| KEY                           |
| KEYS                          |
| KEY_BLOCK_SIZE                |
| KILL                          |
| LANGUAGE                      |
| LAST                          |
| LAST_VALUE                    |
| LASTVAL                       |
| LEADING                       |
| LEAVE                         |
| LEAVES                        |
| LEFT                          |
| LESS                          |
| LEVEL                         |
| LIKE                          |
| LIMIT                         |
| LINEAR                        |
| LINES                         |
| LIST                          |
| LOAD                          |
| LOCAL                         |
| LOCALTIME                     |
| LOCALTIMESTAMP                |
| LOCK                          |
| LOCKED                        |
| LOCKS                         |
| LOGFILE                       |
| LOGS                          |
| LONG                          |
| LONGBLOB                      |
| LONGTEXT                      |
| LOOP                          |
| LOW_PRIORITY                  |
| MASTER                        |
| MASTER_CONNECT_RETRY          |
| MASTER_DELAY                  |
| MASTER_GTID_POS               |
| MASTER_HOST                   |
| MASTER_LOG_FILE               |
| MASTER_LOG_POS                |
| MASTER_PASSWORD               |
| MASTER_PORT                   |
| MASTER_SERVER_ID              |
| MASTER_SSL                    |
| MASTER_SSL_CA                 |
| MASTER_SSL_CAPATH             |
| MASTER_SSL_CERT               |
| MASTER_SSL_CIPHER             |
| MASTER_SSL_CRL                |
| MASTER_SSL_CRLPATH            |
| MASTER_SSL_KEY                |
| MASTER_SSL_VERIFY_SERVER_CERT |
| MASTER_USER                   |
| MASTER_USE_GTID               |
| MASTER_HEARTBEAT_PERIOD       |
| MATCH                         |
| MAX_CONNECTIONS_PER_HOUR      |
| MAX_QUERIES_PER_HOUR          |
| MAX_ROWS                      |
| MAX_SIZE                      |
| MAX_STATEMENT_TIME            |
| MAX_UPDATES_PER_HOUR          |
| MAX_USER_CONNECTIONS          |
| MAXVALUE                      |
| MEDIUM                        |
| MEDIUMBLOB                    |
| MEDIUMINT                     |
| MEDIUMTEXT                    |
| MEMORY                        |
| MERGE                         |
| MESSAGE_TEXT                  |
| MICROSECOND                   |
| MIDDLEINT                     |
| MIGRATE                       |
| MINUS                         |
| MINUTE                        |
| MINUTE_MICROSECOND            |
| MINUTE_SECOND                 |
| MINVALUE                      |
| MIN_ROWS                      |
| MOD                           |
| MODE                          |
| MODIFIES                      |
| MODIFY                        |
| MONITOR                       |
| MONTH                         |
| MUTEX                         |
| MYSQL                         |
| MYSQL_ERRNO                   |
| NAME                          |
| NAMES                         |
| NATIONAL                      |
| NATURAL                       |
| NCHAR                         |
| NESTED                        |
| NEVER                         |
| NEW                           |
| NEXT                          |
| NEXTVAL                       |
| NO                            |
| NOMAXVALUE                    |
| NOMINVALUE                    |
| NOCACHE                       |
| NOCYCLE                       |
| NO_WAIT                       |
| NOWAIT                        |
| NODEGROUP                     |
| NONE                          |
| NOT                           |
| NOTFOUND                      |
| NO_WRITE_TO_BINLOG            |
| NULL                          |
| NUMBER                        |
| NUMERIC                       |
| NVARCHAR                      |
| OF                            |
| OFFSET                        |
| OLD_PASSWORD                  |
| ON                            |
| ONE                           |
| ONLINE                        |
| ONLY                          |
| OPEN                          |
| OPTIMIZE                      |
| OPTIONS                       |
| OPTION                        |
| OPTIONALLY                    |
| OR                            |
| ORDER                         |
| ORDINALITY                    |
| OTHERS                        |
| OUT                           |
| OUTER                         |
| OUTFILE                       |
| OVER                          |
| OVERLAPS                      |
| OWNER                         |
| PACKAGE                       |
| PACK_KEYS                     |
| PAGE                          |
| PAGE_CHECKSUM                 |
| PARSER                        |
| PARSE_VCOL_EXPR               |
| PATH                          |
| PERIOD                        |
| PARTIAL                       |
| PARTITION                     |
| PARTITIONING                  |
| PARTITIONS                    |
| PASSWORD                      |
| PERSISTENT                    |
| PHASE                         |
| PLUGIN                        |
| PLUGINS                       |
| PORT                          |
| PORTION                       |
| PRECEDES                      |
| PRECEDING                     |
| PRECISION                     |
| PREPARE                       |
| PRESERVE                      |
| PREV                          |
| PREVIOUS                      |
| PRIMARY                       |
| PRIVILEGES                    |
| PROCEDURE                     |
| PROCESS                       |
| PROCESSLIST                   |
| PROFILE                       |
| PROFILES                      |
| PROXY                         |
| PURGE                         |
| QUARTER                       |
| QUERY                         |
| QUICK                         |
| RAISE                         |
| RANGE                         |
| RAW                           |
| READ                          |
| READ_ONLY                     |
| READ_WRITE                    |
| READS                         |
| REAL                          |
| REBUILD                       |
| RECOVER                       |
| RECURSIVE                     |
| REDO_BUFFER_SIZE              |
| REDOFILE                      |
| REDUNDANT                     |
| REFERENCES                    |
| REGEXP                        |
| RELAY                         |
| RELAYLOG                      |
| RELAY_LOG_FILE                |
| RELAY_LOG_POS                 |
| RELAY_THREAD                  |
| RELEASE                       |
| RELOAD                        |
| REMOVE                        |
| RENAME                        |
| REORGANIZE                    |
| REPAIR                        |
| REPEATABLE                    |
| REPLACE                       |
| REPLAY                        |
| REPLICA                       |
| REPLICAS                      |
| REPLICA_POS                   |
| REPLICATION                   |
| REPEAT                        |
| REQUIRE                       |
| RESET                         |
| RESIGNAL                      |
| RESTART                       |
| RESTORE                       |
| RESTRICT                      |
| RESUME                        |
| RETURNED_SQLSTATE             |
| RETURN                        |
| RETURNING                     |
| RETURNS                       |
| REUSE                         |
| REVERSE                       |
| REVOKE                        |
| RIGHT                         |
| RLIKE                         |
| ROLE                          |
| ROLLBACK                      |
| ROLLUP                        |
| ROUTINE                       |
| ROW                           |
| ROWCOUNT                      |
| ROWNUM                        |
| ROWS                          |
| ROWTYPE                       |
| ROW_COUNT                     |
| ROW_FORMAT                    |
| RTREE                         |
| SAVEPOINT                     |
| SCHEDULE                      |
| SCHEMA                        |
| SCHEMA_NAME                   |
| SCHEMAS                       |
| SECOND                        |
| SECOND_MICROSECOND            |
| SECURITY                      |
| SELECT                        |
| SENSITIVE                     |
| SEPARATOR                     |
| SEQUENCE                      |
| SERIAL                        |
| SERIALIZABLE                  |
| SESSION                       |
| SERVER                        |
| SET                           |
| SETVAL                        |
| SHARE                         |
| SHOW                          |
| SHUTDOWN                      |
| SIGNAL                        |
| SIGNED                        |
| SIMPLE                        |
| SKIP                          |
| SLAVE                         |
| SLAVES                        |
| SLAVE_POS                     |
| SLOW                          |
| SNAPSHOT                      |
| SMALLINT                      |
| SOCKET                        |
| SOFT                          |
| SOME                          |
| SONAME                        |
| SOUNDS                        |
| SOURCE                        |
| STAGE                         |
| STORED                        |
| SPATIAL                       |
| SPECIFIC                      |
| REF_SYSTEM_ID                 |
| SQL                           |
| SQLEXCEPTION                  |
| SQLSTATE                      |
| SQLWARNING                    |
| SQL_BIG_RESULT                |
| SQL_BUFFER_RESULT             |
| SQL_CACHE                     |
| SQL_CALC_FOUND_ROWS           |
| SQL_NO_CACHE                  |
| SQL_SMALL_RESULT              |
| SQL_THREAD                    |
| SQL_TSI_SECOND                |
| SQL_TSI_MINUTE                |
| SQL_TSI_HOUR                  |
| SQL_TSI_DAY                   |
| SQL_TSI_WEEK                  |
| SQL_TSI_MONTH                 |
| SQL_TSI_QUARTER               |
| SQL_TSI_YEAR                  |
| SSL                           |
| START                         |
| STARTING                      |
| STARTS                        |
| STATEMENT                     |
| STATS_AUTO_RECALC             |
| STATS_PERSISTENT              |
| STATS_SAMPLE_PAGES            |
| STATUS                        |
| STOP                          |
| STORAGE                       |
| STRAIGHT_JOIN                 |
| STRING                        |
| SUBCLASS_ORIGIN               |
| SUBJECT                       |
| SUBPARTITION                  |
| SUBPARTITIONS                 |
| SUPER                         |
| SUSPEND                       |
| SWAPS                         |
| SWITCHES                      |
| SYSDATE                       |
| SYSTEM                        |
| SYSTEM_TIME                   |
| TABLE                         |
| TABLE_NAME                    |
| TABLES                        |
| TABLESPACE                    |
| TABLE_CHECKSUM                |
| TEMPORARY                     |
| TEMPTABLE                     |
| TERMINATED                    |
| TEXT                          |
| THAN                          |
| THEN                          |
| TIES                          |
| TIME                          |
| TIMESTAMP                     |
| TIMESTAMPADD                  |
| TIMESTAMPDIFF                 |
| TINYBLOB                      |
| TINYINT                       |
| TINYTEXT                      |
| TO                            |
| TRAILING                      |
| TRANSACTION                   |
| TRANSACTIONAL                 |
| THREADS                       |
| TRIGGER                       |
| TRIGGERS                      |
| TRUE                          |
| TRUNCATE                      |
| TYPE                          |
| TYPES                         |
| UNBOUNDED                     |
| UNCOMMITTED                   |
| UNDEFINED                     |
| UNDO_BUFFER_SIZE              |
| UNDOFILE                      |
| UNDO                          |
| UNICODE                       |
| UNION                         |
| UNIQUE                        |
| UNKNOWN                       |
| UNLOCK                        |
| UNINSTALL                     |
| UNSIGNED                      |
| UNTIL                         |
| UPDATE                        |
| UPGRADE                       |
| USAGE                         |
| USE                           |
| USER                          |
| USER_RESOURCES                |
| USE_FRM                       |
| USING                         |
| UTC_DATE                      |
| UTC_TIME                      |
| UTC_TIMESTAMP                 |
| VALUE                         |
| VALUES                        |
| VARBINARY                     |
| VARCHAR                       |
| VARCHARACTER                  |
| VARCHAR2                      |
| VARIABLES                     |
| VARYING                       |
| VIA                           |
| VIEW                          |
| VIRTUAL                       |
| VISIBLE                       |
| VERSIONING                    |
| WAIT                          |
| WARNINGS                      |
| WEEK                          |
| WEIGHT_STRING                 |
| WHEN                          |
| WHERE                         |
| WHILE                         |
| WINDOW                        |
| WITH                          |
| WITHIN                        |
| WITHOUT                       |
| WORK                          |
| WRAPPER                       |
| WRITE                         |
| X509                          |
| XOR                           |
| XA                            |
| XML                           |
| YEAR                          |
| YEAR_MONTH                    |
| ZEROFILL                      |
| ||                            |
+-------------------------------+
694 rows in set (0.000 sec)

See Also

1.1.1.2.9.1.1.26 Information Schema LOCALES Table

Description

The Information Schema LOCALES table contains a list of all compiled-in locales. It is only available if the LOCALES plugin has been installed.

It contains the following columns:

ColumnDescription
IDRow ID.
NAMELocale name, for example en_GB.
DESCRIPTIONLocale description, for example English - United Kingdom.
MAX_MONTH_NAME_LENGTHNumeric length of the longest month in the locale
MAX_DAY_NAME_LENGTHNumeric length of the longest day name in the locale.
DECIMAL_POINTDecimal point character (some locales use a comma).
THOUSAND_SEPThousand's character separator,
ERROR_MESSAGE_LANGUAGEError message language.

The table is not a standard Information Schema table, and is a MariaDB extension.

The SHOW LOCALES statement returns a subset of the information.

Example

SELECT * FROM information_schema.LOCALES;
+-----+-------+-------------------------------------+-----------------------+---------------------+---------------+--------------+------------------------+
| ID  | NAME  | DESCRIPTION                         | MAX_MONTH_NAME_LENGTH | MAX_DAY_NAME_LENGTH | DECIMAL_POINT | THOUSAND_SEP | ERROR_MESSAGE_LANGUAGE |
+-----+-------+-------------------------------------+-----------------------+---------------------+---------------+--------------+------------------------+
|   0 | en_US | English - United States             |                     9 |                   9 | .             | ,            | english                |
|   1 | en_GB | English - United Kingdom            |                     9 |                   9 | .             | ,            | english                |
|   2 | ja_JP | Japanese - Japan                    |                     3 |                   3 | .             | ,            | japanese               |
|   3 | sv_SE | Swedish - Sweden                    |                     9 |                   7 | ,             |              | swedish                |
|   4 | de_DE | German - Germany                    |                     9 |                  10 | ,             | .            | german                 |
|   5 | fr_FR | French - France                     |                     9 |                   8 | ,             |              | french                 |
|   6 | ar_AE | Arabic - United Arab Emirates       |                     6 |                   8 | .             | ,            | english                |
|   7 | ar_BH | Arabic - Bahrain                    |                     6 |                   8 | .             | ,            | english                |
|   8 | ar_JO | Arabic - Jordan                     |                    12 |                   8 | .             | ,            | english                |
...
| 106 | no_NO | Norwegian - Norway                  |                     9 |                   7 | ,             | .            | norwegian              |
| 107 | sv_FI | Swedish - Finland                   |                     9 |                   7 | ,             |              | swedish                |
| 108 | zh_HK | Chinese - Hong Kong SAR             |                     3 |                   3 | .             | ,            | english                |
| 109 | el_GR | Greek - Greece                      |                    11 |                   9 | ,             | .            | greek                  |
+-----+-------+-------------------------------------+-----------------------+---------------------+---------------+--------------+------------------------+

1.1.1.2.9.1.1.27 Information Schema METADATA_LOCK_INFO Table

The Information Schema METADATA_LOCK_INFO table is created by the metadata_lock_info plugin. It shows active metadata locks and user locks (the locks acquired with GET_LOCK).

It has the following columns:

ColumnDescription
THREAD_ID
LOCK_MODEOne of MDL_INTENTION_EXCLUSIVE, MDL_SHARED, MDL_SHARED_HIGH_PRIO, MDL_SHARED_READ, MDL_SHARED_READ_ONLY, MDL_SHARED_WRITE, MDL_SHARED_NO_WRITE, MDL_SHARED_NO_READ_WRITE, MDL_SHARED_UPGRADABLE or MDL_EXCLUSIVE.
LOCK_DURATIONOne of MDL_STATEMENT, MDL_TRANSACTION or MDL_EXPLICIT
LOCK_TYPEOne of Global read lock, Schema metadata lock, Table metadata lock, Stored function metadata lock, Stored procedure metadata lock, Trigger metadata lock, Event metadata lock, Commit lock or User lock.
TABLE_SCHEMA
TABLE_NAME

"LOCK_MODE" Descriptions

The LOCK_MODE column can have the following values:

ValueDescription
MDL_INTENTION_EXCLUSIVEAn intention exclusive metadata lock (IX). Used only for scoped locks. Owner of this type of lock can acquire upgradable exclusive locks on individual objects. Compatible with other IX locks, but is incompatible with scoped S and X locks. IX lock is taken in SCHEMA namespace when we intend to modify object metadata. Object may refer table, stored procedure, trigger, view/etc.
MDL_SHAREDA shared metadata lock (S). To be used in cases when we are interested in object metadata only and there is no intention to access object data (e.g. for stored routines or during preparing prepared statements). We also mis-use this type of lock for open HANDLERs, since lock acquired by this statement has to be compatible with lock acquired by LOCK TABLES ... WRITE statement, i.e. SNRW (We can't get by by acquiring S lock at HANDLER ... OPEN time and upgrading it to SR lock for HANDLER ... READ as it doesn't solve problem with need to abort DML statements which wait on table level lock while having open HANDLER in the same connection). To avoid deadlock which may occur when SNRW lock is being upgraded to X lock for table on which there is an active S lock which is owned by thread which waits in its turn for table-level lock owned by thread performing upgrade we have to use thr_abort_locks_for_thread() facility in such situation. This problem does not arise for locks on stored routines as we don't use SNRW locks for them. It also does not arise when S locks are used during PREPARE calls as table-level locks are not acquired in this case. This lock is taken for global read lock, when caching a stored procedure in memory for the duration of the transaction and for tables used by prepared statements.
MDL_SHARED_HIGH_PRIOA high priority shared metadata lock. Used for cases when there is no intention to access object data (i.e. data in the table). "High priority" means that, unlike other shared locks, it is granted ignoring pending requests for exclusive locks. Intended for use in cases when we only need to access metadata and not data, e.g. when filling an INFORMATION_SCHEMA table. Since SH lock is compatible with SNRW lock, the connection that holds SH lock lock should not try to acquire any kind of table-level or row-level lock, as this can lead to a deadlock. Moreover, after acquiring SH lock, the connection should not wait for any other resource, as it might cause starvation for X locks and a potential deadlock during upgrade of SNW or SNRW to X lock (e.g. if the upgrading connection holds the resource that is being waited for).
MDL_SHARED_READA shared metadata lock (SR) for cases when there is an intention to read data from table. A connection holding this kind of lock can read table metadata and read table data (after acquiring appropriate table and row-level locks). This means that one can only acquire TL_READ, TL_READ_NO_INSERT, and similar table-level locks on table if one holds SR MDL lock on it. To be used for tables in SELECTs, subqueries, and LOCK TABLE ... READ statements.
MDL_SHARED_WRITEA shared metadata lock (SW) for cases when there is an intention to modify (and not just read) data in the table. A connection holding SW lock can read table metadata and modify or read table data (after acquiring appropriate table and row-level locks). To be used for tables to be modified by INSERT, UPDATE, DELETE statements, but not LOCK TABLE ... WRITE or DDL). Also taken by SELECT ... FOR UPDATE.
MDL_SHARED_UPGRADABLEAn upgradable shared metadata lock for cases when there is an intention to modify (and not just read) data in the table. Can be upgraded to MDL_SHARED_NO_WRITE and MDL_EXCLUSIVE. A connection holding SU lock can read table metadata and modify or read table data (after acquiring appropriate table and row-level locks). To be used for the first phase of ALTER TABLE.
MDL_SHARED_READ_ONLYA shared metadata lock for cases when we need to read data from table and block all concurrent modifications to it (for both data and metadata). Used by LOCK TABLES READ statement.
MDL_SHARED_NO_WRITEAn upgradable shared metadata lock which blocks all attempts to update table data, allowing reads. A connection holding this kind of lock can read table metadata and read table data. Can be upgraded to X metadata lock. Note, that since this type of lock is not compatible with SNRW or SW lock types, acquiring appropriate engine-level locks for reading (TL_READ* for MyISAM, shared row locks in InnoDB) should be contention-free. To be used for the first phase of ALTER TABLE, when copying data between tables, to allow concurrent SELECTs from the table, but not UPDATEs.
MDL_SHARED_NO_READ_WRITEAn upgradable shared metadata lock which allows other connections to access table metadata, but not data. It blocks all attempts to read or update table data, while allowing INFORMATION_SCHEMA and SHOW queries. A connection holding this kind of lock can read table metadata modify and read table data. Can be upgraded to X metadata lock. To be used for LOCK TABLES WRITE statement. Not compatible with any other lock type except S and SH.
MDL_EXCLUSIVEAn exclusive metadata lock (X). A connection holding this lock can modify both table's metadata and data. No other type of metadata lock can be granted while this lock is held. To be used for CREATE/DROP/RENAME TABLE statements and for execution of certain phases of other DDL statements.

Examples

User lock:

SELECT GET_LOCK('abc',1000);
+----------------------+
| GET_LOCK('abc',1000) |
+----------------------+
|                    1 |
+----------------------+

SELECT * FROM information_schema.METADATA_LOCK_INFO;
+-----------+--------------------------+---------------+-----------+--------------+------------+
| THREAD_ID | LOCK_MODE                | LOCK_DURATION | LOCK_TYPE | TABLE_SCHEMA | TABLE_NAME |
+-----------+--------------------------+---------------+-----------+--------------+------------+
|        61 | MDL_SHARED_NO_READ_WRITE | MDL_EXPLICIT  | User lock | abc          |            |
+-----------+--------------------------+---------------+-----------+--------------+------------+

Table metadata lock:

START TRANSACTION;

INSERT INTO t VALUES (1,2);

SELECT * FROM information_schema.METADATA_LOCK_INFO \G
*************************** 1. row ***************************
    THREAD_ID: 4
    LOCK_MODE: MDL_SHARED_WRITE
LOCK_DURATION: MDL_TRANSACTION
    LOCK_TYPE: Table metadata lock
 TABLE_SCHEMA: test
   TABLE_NAME: t

SELECT * FROM information_schema.METADATA_LOCK_INFO;
+-----------+--------------------------+---------------+----------------------+-----------------+-------------+
| THREAD_ID | LOCK_MODE | LOCK_DURATION | LOCK_TYPE | TABLE_SCHEMA | TABLE_NAME |
+-----------+--------------------------+---------------+----------------------+-----------------+-------------+ 
| 31 | MDL_INTENTION_EXCLUSIVE | MDL_EXPLICIT | Global read lock | | |
| 31 | MDL_INTENTION_EXCLUSIVE | MDL_EXPLICIT | Commit lock | | |
| 31 | MDL_INTENTION_EXCLUSIVE | MDL_EXPLICIT | Schema metadata lock | dbname | |
| 31 | MDL_SHARED_NO_READ_WRITE | MDL_EXPLICIT | Table metadata lock | dbname | exotics |
+-----------+--------------------------+---------------+----------------------+-----------------+-------------+

See also

1.1.1.2.9.1.1.28 Information Schema MROONGA_STATS Table

The Information Schema MROONGA_STATS table only exists if the Mroonga storage engine is installed, and contains information about its activities.

ColumnDescription
VERSIONMroonga version.
rows_writtenNumber of rows written into Mroonga tables.
rows_readNumber of rows read from all Mroonga tables.

This table always contains 1 row.

1.1.1.2.9.1.1.29 Information Schema OPTIMIZER_TRACE Table

MariaDB starting with 10.4.3

Optimizer Trace was introduced in MariaDB 10.4.3.

Description

The Information Schema OPTIMIZER_TRACE table contains Optimizer Trace information.

It contains the following columns:

ColumnDescription
QUERYDisplays the query that was asked to be traced.
TRACEA JSON document displaying the stats we collected when the query was run.
MISSING_BYTES_BEYOND_MAX_MEM_SIZEFor huge trace, where the trace is truncated due to the optimizer_trace_max_mem_size limit being reached, displays the bytes that are missing in the trace
INSUFFICENT_PRIVILEGESSet to 1 if the user running the trace does not have the privileges to see the trace.

Structure:

SHOW CREATE TABLE INFORMATION_SCHEMA.OPTIMIZER_TRACE \G
*************************** 1. row ***************************
       Table: OPTIMIZER_TRACE
Create Table: CREATE TEMPORARY TABLE `OPTIMIZER_TRACE` (
  `QUERY` longtext NOT NULL DEFAULT '',
  `TRACE` longtext NOT NULL DEFAULT '',
  `MISSING_BYTES_BEYOND_MAX_MEM_SIZE` int(20) NOT NULL DEFAULT 0,
  `INSUFFICIENT_PRIVILEGES` tinyint(1) NOT NULL DEFAULT 0
) ENGINE=Aria DEFAULT CHARSET=utf8 PAGE_CHECKSUM=0

1.1.1.2.9.1.1.30 Information Schema PARAMETERS Table

The Information Schema PARAMETERS table stores information about stored procedures and stored functions parameters.

It contains the following columns:

ColumnDescription
SPECIFIC_CATALOGAlways def.
SPECIFIC_SCHEMADatabase name containing the stored routine parameter.
SPECIFIC_NAMEStored routine name.
ORDINAL_POSITIONOrdinal position of the parameter, starting at 1. 0 for a function RETURNS clause.
PARAMETER_MODEOne of IN, OUT, INOUT or NULL for RETURNS.
PARAMETER_NAMEName of the parameter, or NULL for RETURNS.
DATA_TYPEThe column's data type.
CHARACTER_MAXIMUM_LENGTHMaximum length.
CHARACTER_OCTET_LENGTHSame as the CHARACTER_MAXIMUM_LENGTH except for multi-byte character sets.
NUMERIC_PRECISIONFor numeric types, the precision (number of significant digits) for the column. NULL if not a numeric field.
NUMERIC_SCALEFor numeric types, the scale (significant digits to the right of the decimal point). NULL if not a numeric field.
DATETIME_PRECISIONFractional-seconds precision, or NULL if not a time data type.
CHARACTER_SET_NAMECharacter set if a non-binary string data type, otherwise NULL.
COLLATION_NAMECollation if a non-binary string data type, otherwise NULL.
DTD_IDENTIFIERDescription of the data type.
ROUTINE_TYPEPROCEDURE or FUNCTION.

Information from this table is similar to that found in the param_list column in the mysql.proc table, and the output of the SHOW CREATE PROCEDURE and SHOW CREATE FUNCTION statements.

To obtain information about the routine itself, you can query the Information Schema ROUTINES table.

Example

SELECT * FROM information_schema.PARAMETERS
LIMIT 1 \G
********************** 1. row **********************
        SPECIFIC_CATALOG: def
         SPECIFIC_SCHEMA: accounts
           SPECIFIC_NAME: user_counts
        ORDINAL_POSITION: 1
          PARAMETER_MODE: IN
          PARAMETER_NAME: user_order
               DATA_TYPE: varchar
CHARACTER_MAXIMUM_LENGTH: 255
  CHARACTER_OCTET_LENGTH: 765
       NUMERIC_PRECISION: NULL
           NUMERIC_SCALE: NULL
      DATETIME_PRECISION: NULL
      CHARACTER_SET_NAME: utf8
          COLLATION_NAME: utf8_general_ci
          DTD_IDENTIFIER: varchar(255)
            ROUTINE_TYPE: PROCEDURE

1.1.1.2.9.1.1.31 Information Schema PARTITIONS Table

The Information Schema PARTITIONS contains information about table partitions, with each record corresponding to a single partition or subpartition of a partitioned table. Each non-partitioned table also has a record in the PARTITIONS table, but most of the values are NULL.

It contains the following columns:

ColumnDescription
TABLE_CATALOGAlways def.
TABLE_SCHEMADatabase name.
TABLE_NAMETable name containing the partition.
PARTITION_NAMEPartition name.
SUBPARTITION_NAMESubpartition name, or NULL if not a subpartition.
PARTITION_ORDINAL_POSITIONOrder of the partition starting from 1.
SUBPARTITION_ORDINAL_POSITIONOrder of the subpartition starting from 1.
PARTITION_METHODThe partitioning type; one of RANGE, LIST, HASH, LINEAR HASH, KEY or LINEAR KEY.
SUBPARTITION_METHODSubpartition type; one of HASH, LINEAR HASH, KEY or LINEAR KEY, or NULL if not a subpartition.
PARTITION_EXPRESSIONExpression used to create the partition by the CREATE TABLE or ALTER TABLE statement.
SUBPARTITION_EXPRESSIONExpression used to create the subpartition by the CREATE TABLE or ALTER TABLE statement, or NULL if not a subpartition.
PARTITION_DESCRIPTIONFor a RANGE partition, contains either MAXINTEGER or an integer, as set in the VALUES LESS THAN clause. For a LIST partition, contains a comma-separated list of integers, as set in the VALUES IN. NULL if another type of partition.
TABLE_ROWSNumber of rows in the table (may be an estimate for some storage engines).
AVG_ROW_LENGTHAverage row length, that is DATA_LENGTH divided by TABLE_ROWS
DATA_LENGTHTotal number of bytes stored in all rows of the partition.
MAX_DATA_LENGTHMaximum bytes that could be stored in the partition.
INDEX_LENGTHSize in bytes of the partition index file.
DATA_FREEUnused bytes allocated to the partition.
CREATE_TIMETime the partition was created
UPDATE_TIMETime the partition was last modified.
CHECK_TIMETime the partition was last checked, or NULL for storage engines that don't record this information.
CHECKSUMChecksum value, or NULL if none.
PARTITION_COMMENTPartition comment, truncated to 80 characters, or an empty string if no comment.
NODEGROUPNode group, only used for MySQL Cluster, defaults to 0.
TABLESPACE_NAMEAlways default.

1.1.1.2.9.1.1.32 Information Schema PLUGINS Table

The Information Schema PLUGINS table contains information about server plugins.

It contains the following columns:

ColumnDescription
PLUGIN_NAMEName of the plugin.
PLUGIN_VERSIONVersion from the plugin's general type descriptor.
PLUGIN_STATUSPlugin status, one of ACTIVE, INACTIVE, DISABLED or DELETED.
PLUGIN_TYPEPlugin type; STORAGE ENGINE, INFORMATION_SCHEMA, AUTHENTICATION, REPLICATION, DAEMON or AUDIT.
PLUGIN_TYPE_VERSIONVersion from the plugin's type-specific descriptor.
PLUGIN_LIBRARYPlugin's shared object file name, located in the directory specified by the plugin_dir system variable, and used by the INSTALL PLUGIN and UNINSTALL PLUGIN statements. NULL if the plugin is complied in and cannot be uninstalled.
PLUGIN_LIBRARY_VERSIONVersion from the plugin's API interface.
PLUGIN_AUTHORAuthor of the plugin.
PLUGIN_DESCRIPTIONDescription.
PLUGIN_LICENSEPlugin's licence.
LOAD_OPTIONHow the plugin was loaded; one of OFF, ON, FORCE or FORCE_PLUS_PERMANENT. See Installing Plugins.
PLUGIN_MATURITYPlugin's maturity level; one of Unknown, Experimental, Alpha, Beta,'Gamma, and Stable.
PLUGIN_AUTH_VERSIONPlugin's version as determined by the plugin author. An example would be '0.99 beta 1'.

It provides a superset of the information shown by the SHOW PLUGINS statement. For specific information about storage engines (a particular type of plugins), see the information_schema.ENGINES table and the SHOW ENGINES statement.

This table provides a subset of the Information Schema information_schema.ALL_PLUGINS table, which contains all available plugins, installed or not.

The table is not a standard Information Schema table, and is a MariaDB extension.

Examples

The easiest way to get basic information on plugins is with SHOW PLUGINS:

SHOW PLUGINS;

+----------------------------+----------+--------------------+-------------+---------+
| Name                       | Status   | Type               | Library     | License |
+----------------------------+----------+--------------------+-------------+---------+
| binlog                     | ACTIVE   | STORAGE ENGINE     | NULL        | GPL     |
| mysql_native_password      | ACTIVE   | AUTHENTICATION     | NULL        | GPL     |
| mysql_old_password         | ACTIVE   | AUTHENTICATION     | NULL        | GPL     |
| MRG_MyISAM                 | ACTIVE   | STORAGE ENGINE     | NULL        | GPL     |
| MyISAM                     | ACTIVE   | STORAGE ENGINE     | NULL        | GPL     |
| CSV                        | ACTIVE   | STORAGE ENGINE     | NULL        | GPL     |
| MEMORY                     | ACTIVE   | STORAGE ENGINE     | NULL        | GPL     |
| FEDERATED                  | ACTIVE   | STORAGE ENGINE     | NULL        | GPL     |
| PERFORMANCE_SCHEMA         | ACTIVE   | STORAGE ENGINE     | NULL        | GPL     |
| Aria                       | ACTIVE   | STORAGE ENGINE     | NULL        | GPL     |
| InnoDB                     | ACTIVE   | STORAGE ENGINE     | NULL        | GPL     |
| INNODB_TRX                 | ACTIVE   | INFORMATION SCHEMA | NULL        | GPL     |
| INNODB_LOCKS               | ACTIVE   | INFORMATION SCHEMA | NULL        | GPL     |
| INNODB_LOCK_WAITS          | ACTIVE   | INFORMATION SCHEMA | NULL        | GPL     |
| INNODB_CMP                 | ACTIVE   | INFORMATION SCHEMA | NULL        | GPL     |
| INNODB_CMP_RESET           | ACTIVE   | INFORMATION SCHEMA | NULL        | GPL     |
| INNODB_CMPMEM              | ACTIVE   | INFORMATION SCHEMA | NULL        | GPL     |
| INNODB_CMPMEM_RESET        | ACTIVE   | INFORMATION SCHEMA | NULL        | GPL     |
| INNODB_BUFFER_PAGE         | ACTIVE   | INFORMATION SCHEMA | NULL        | GPL     |
| INNODB_BUFFER_PAGE_LRU     | ACTIVE   | INFORMATION SCHEMA | NULL        | GPL     |
| INNODB_BUFFER_POOL_STATS   | ACTIVE   | INFORMATION SCHEMA | NULL        | GPL     |
| INNODB_METRICS             | ACTIVE   | INFORMATION SCHEMA | NULL        | GPL     |
| INNODB_FT_DEFAULT_STOPWORD | ACTIVE   | INFORMATION SCHEMA | NULL        | GPL     |
| INNODB_FT_INSERTED         | ACTIVE   | INFORMATION SCHEMA | NULL        | GPL     |
| INNODB_FT_DELETED          | ACTIVE   | INFORMATION SCHEMA | NULL        | GPL     |
| INNODB_FT_BEING_DELETED    | ACTIVE   | INFORMATION SCHEMA | NULL        | GPL     |
| INNODB_FT_CONFIG           | ACTIVE   | INFORMATION SCHEMA | NULL        | GPL     |
| INNODB_FT_INDEX_CACHE      | ACTIVE   | INFORMATION SCHEMA | NULL        | GPL     |
| INNODB_FT_INDEX_TABLE      | ACTIVE   | INFORMATION SCHEMA | NULL        | GPL     |
| INNODB_SYS_TABLES          | ACTIVE   | INFORMATION SCHEMA | NULL        | GPL     |
| INNODB_SYS_TABLESTATS      | ACTIVE   | INFORMATION SCHEMA | NULL        | GPL     |
| INNODB_SYS_INDEXES         | ACTIVE   | INFORMATION SCHEMA | NULL        | GPL     |
| INNODB_SYS_COLUMNS         | ACTIVE   | INFORMATION SCHEMA | NULL        | GPL     |
| INNODB_SYS_FIELDS          | ACTIVE   | INFORMATION SCHEMA | NULL        | GPL     |
| INNODB_SYS_FOREIGN         | ACTIVE   | INFORMATION SCHEMA | NULL        | GPL     |
| INNODB_SYS_FOREIGN_COLS    | ACTIVE   | INFORMATION SCHEMA | NULL        | GPL     |
| SPHINX                     | ACTIVE   | STORAGE ENGINE     | NULL        | GPL     |
| ARCHIVE                    | ACTIVE   | STORAGE ENGINE     | NULL        | GPL     |
| BLACKHOLE                  | ACTIVE   | STORAGE ENGINE     | NULL        | GPL     |
| FEEDBACK                   | DISABLED | INFORMATION SCHEMA | NULL        | GPL     |
| partition                  | ACTIVE   | STORAGE ENGINE     | NULL        | GPL     |
| pam                        | ACTIVE   | AUTHENTICATION     | auth_pam.so | GPL     |
+----------------------------+----------+--------------------+-------------+---------+

SELECT LOAD_OPTION 
FROM INFORMATION_SCHEMA.PLUGINS 
WHERE PLUGIN_NAME LIKE 'tokudb';
Empty set

The equivalent SELECT query would be:

SELECT PLUGIN_NAME, PLUGIN_STATUS, 
PLUGIN_TYPE, PLUGIN_LIBRARY, PLUGIN_LICENSE
FROM INFORMATION_SCHEMA.PLUGINS;

Other SELECT queries can be used to see additional information. For example:

SELECT PLUGIN_NAME, PLUGIN_DESCRIPTION, 
PLUGIN_MATURITY, PLUGIN_AUTH_VERSION
FROM INFORMATION_SCHEMA.PLUGINS
WHERE PLUGIN_TYPE='STORAGE ENGINE'
ORDER BY PLUGIN_MATURITY \G

*************************** 1. row ***************************
        PLUGIN_NAME: FEDERATED
 PLUGIN_DESCRIPTION: FederatedX pluggable storage engine
    PLUGIN_MATURITY: Beta
PLUGIN_AUTH_VERSION: 2.1
*************************** 2. row ***************************
        PLUGIN_NAME: Aria
 PLUGIN_DESCRIPTION: Crash-safe tables with MyISAM heritage
    PLUGIN_MATURITY: Gamma
PLUGIN_AUTH_VERSION: 1.5
*************************** 3. row ***************************
        PLUGIN_NAME: PERFORMANCE_SCHEMA
 PLUGIN_DESCRIPTION: Performance Schema
    PLUGIN_MATURITY: Gamma
PLUGIN_AUTH_VERSION: 0.1
*************************** 4. row ***************************
        PLUGIN_NAME: binlog
 PLUGIN_DESCRIPTION: This is a pseudo storage engine to represent the binlog in a transaction
    PLUGIN_MATURITY: Stable
PLUGIN_AUTH_VERSION: 1.0
*************************** 5. row ***************************
        PLUGIN_NAME: MEMORY
 PLUGIN_DESCRIPTION: Hash based, stored in memory, useful for temporary tables
    PLUGIN_MATURITY: Stable
PLUGIN_AUTH_VERSION: 1.0
*************************** 6. row ***************************
        PLUGIN_NAME: MyISAM
 PLUGIN_DESCRIPTION: MyISAM storage engine
    PLUGIN_MATURITY: Stable
PLUGIN_AUTH_VERSION: 1.0
*************************** 7. row ***************************
        PLUGIN_NAME: MRG_MyISAM
 PLUGIN_DESCRIPTION: Collection of identical MyISAM tables
    PLUGIN_MATURITY: Stable
PLUGIN_AUTH_VERSION: 1.0
*************************** 8. row ***************************
        PLUGIN_NAME: CSV
 PLUGIN_DESCRIPTION: CSV storage engine
    PLUGIN_MATURITY: Stable
PLUGIN_AUTH_VERSION: 1.0
*************************** 9. row ***************************
        PLUGIN_NAME: InnoDB
 PLUGIN_DESCRIPTION: Supports transactions, row-level locking, and foreign keys
    PLUGIN_MATURITY: Stable
PLUGIN_AUTH_VERSION: 1.2.5
*************************** 10. row ***************************
        PLUGIN_NAME: BLACKHOLE
 PLUGIN_DESCRIPTION: /dev/null storage engine (anything you write to it disappears)
    PLUGIN_MATURITY: Stable
PLUGIN_AUTH_VERSION: 1.0
*************************** 11. row ***************************
        PLUGIN_NAME: ARCHIVE
 PLUGIN_DESCRIPTION: Archive storage engine
    PLUGIN_MATURITY: Stable
PLUGIN_AUTH_VERSION: 1.0
*************************** 12. row ***************************
        PLUGIN_NAME: partition
 PLUGIN_DESCRIPTION: Partition Storage Engine Helper
    PLUGIN_MATURITY: Stable
PLUGIN_AUTH_VERSION: 1.0

Check if a given plugin is available:

SELECT LOAD_OPTION 
FROM INFORMATION_SCHEMA.PLUGINS 
WHERE PLUGIN_NAME LIKE 'tokudb';
Empty set

Show authentication plugins:

SELECT PLUGIN_NAME, LOAD_OPTION 
FROM INFORMATION_SCHEMA.PLUGINS 
WHERE PLUGIN_TYPE LIKE 'authentication' \G

*************************** 1. row ***************************
PLUGIN_NAME: mysql_native_password
LOAD_OPTION: FORCE
*************************** 2. row ***************************
PLUGIN_NAME: mysql_old_password
LOAD_OPTION: FORCE

See Also

1.1.1.2.9.1.1.33 Information Schema PROCESSLIST Table

Contents

  1. Example
  2. See Also

The Information Schema PROCESSLIST table contains information about running threads.

Similar information can also be returned with the SHOW [FULL] PROCESSLIST statement, or the mysqladmin processlist command.

It contains the following columns:

ColumnDescription
IDConnection identifier.
USERMariaDB User.
HOSTConnecting host.
DBDefault database, or NULL if none.
COMMANDType of command running, corresponding to the Com_ status variables. See Thread Command Values.
TIMESeconds that the thread has spent on the current COMMAND so far.
STATECurrent state of the thread. See Thread States.
INFOStatement the thread is executing, or NULL if none.
TIME_MSTime in milliseconds with microsecond precision that the thread has spent on the current COMMAND so far (see more).
STAGEThe stage the process is currently in.
MAX_STAGEThe maximum number of stages.
PROGRESSThe progress of the process within the current stage (0-100%).
MEMORY_USEDMemory in bytes used by the thread.
EXAMINED_ROWSRows examined by the thread. Only updated by UPDATE, DELETE, and similar statements. For SELECT and other statements, the value remains zero.
QUERY_IDQuery ID.
INFO_BINARYBinary data information
TIDThread ID (MDEV-6756)

Note that as a difference to MySQL, in MariaDB the TIME column (and also the TIME_MS column) are not affected by any setting of @TIMESTAMP. This means that it can be reliably used also for threads that change @TIMESTAMP (such as the replication SQL thread). See also MySQL Bug #22047.

As a consequence of this, the TIME column of SHOW FULL PROCESSLIST and INFORMATION_SCHEMA.PROCESSLIST can not be used to determine if a slave is lagging behind. For this, use instead the Seconds_Behind_Master column in the output of SHOW SLAVE STATUS.

Note that the PROGRESS field from the information schema, and the PROGRESS field from SHOW PROCESSLIST display different results. SHOW PROCESSLIST shows the total progress, while the information schema shows the progress for the current stage only.. To retrieve a similar "total" Progress value from information_schema.PROCESSLIST as the one from SHOW PROCESSLIST, use 

SELECT CASE WHEN Max_Stage < 2 THEN Progress ELSE (Stage-1)/Max_Stage*100+Progress/Max_Stage END 
  AS Progress FROM INFORMATION_SCHEMA.PROCESSLIST;

Example

SELECT * FROM INFORMATION_SCHEMA.PROCESSLIST\G
*************************** 1. row ***************************
           ID: 9
         USER: msandbox
         HOST: localhost
           DB: NULL
      COMMAND: Query
         TIME: 0
        STATE: Filling schema table
         INFO: SELECT * FROM INFORMATION_SCHEMA.PROCESSLIST
      TIME_MS: 0.351
        STAGE: 0
    MAX_STAGE: 0
     PROGRESS: 0.000
  MEMORY_USED: 85392
EXAMINED_ROWS: 0
     QUERY_ID: 15
  INFO_BINARY: SELECT * FROM INFORMATION_SCHEMA.PROCESSLIST
          TID: 11838
*************************** 2. row ***************************
           ID: 5
         USER: system user
         HOST: 
           DB: NULL
      COMMAND: Daemon
         TIME: 0
        STATE: InnoDB shutdown handler
         INFO: NULL
      TIME_MS: 0.000
        STAGE: 0
    MAX_STAGE: 0
     PROGRESS: 0.000
  MEMORY_USED: 24160
EXAMINED_ROWS: 0
     QUERY_ID: 0
  INFO_BINARY: NULL
          TID: 3856
...

See Also

1.1.1.2.9.1.1.34 Information Schema PROFILING Table

The Information Schema PROFILING table contains information about statement resource usage. Profiling information is only recorded if the profiling session variable is set to 1.

It contains the following columns:

Column NameDescription
QUERY_IDQuery_ID.
SEQSequence number showing the display order for rows with the same QUERY_ID.
STATEProfiling state.
DURATIONTime in seconds that the statement has been in the current state.
CPU_USERUser CPU usage in seconds.
CPU_SYSTEMSystem CPU usage in seconds.
CONTEXT_VOLUNTARYNumber of voluntary context switches.
CONTEXT_INVOLUNTARYNumber of involuntary context switches.
BLOCK_OPS_INNumber of block input operations.
BLOCK_OPS_OUTNumber of block output operations.
MESSAGES_SENTNumber of communications sent.
MESSAGES_RECEIVEDNumber of communications received.
PAGE_FAULTS_MAJORNumber of major page faults.
PAGE_FAULTS_MINORNumber of minor page faults.
SWAPSNumber of swaps.
SOURCE_FUNCTIONFunction in the source code executed by the profiled state.
SOURCE_FILEFile in the source code executed by the profiled state.
SOURCE_LINELine in the source code executed by the profiled state.

It contains similar information to the SHOW PROFILE and SHOW PROFILES statements.

Profiling is enabled per session. When a session ends, its profiling information is lost.

1.1.1.2.9.1.1.35 Information Schema QUERY_CACHE_INFO Table

Description

The table is not a standard Information Schema table, and is a MariaDB extension.

The QUERY_CACHE_INFO table is created by the QUERY_CACHE_INFO plugin, and allows you to see the contents of the query cache. It creates a table in the information_schema database that shows all queries that are in the cache. You must have the PROCESS privilege (see GRANT) to use this table.

It contains the following columns:

ColumnDescription
STATEMENT_SCHEMADatabase used when query was included
STATEMENT_TEXTQuery text
RESULT_BLOCKS_COUNTNumber of result blocks
RESULT_BLOCKS_SIZESize in bytes of result blocks
RESULT_BLOCKS_SIZE_USEDSize in bytes of used blocks
LIMITAdded MariaDB 10.1.8.
MAX_SORT_LENGTHAdded MariaDB 10.1.8.
GROUP_CONCAT_MAX_LENGTHAdded MariaDB 10.1.8.
CHARACTER_SET_CLIENTAdded MariaDB 10.1.8.
CHARACTER_SET_RESULTAdded MariaDB 10.1.8.
COLLATION Added MariaDB 10.1.8.
TIMEZONEAdded MariaDB 10.1.8.
DEFAULT_WEEK_FORMATAdded MariaDB 10.1.8.
DIV_PRECISION_INCREMENTAdded MariaDB 10.1.8.
SQL_MODEAdded MariaDB 10.1.8.
LC_TIME_NAMESAdded MariaDB 10.1.8.
CLIENT_LONG_FLAGAdded MariaDB 10.1.8.
CLIENT_PROTOCOL_41Added MariaDB 10.1.8.
PROTOCOL_TYPEAdded MariaDB 10.1.8.
MORE_RESULTS_EXISTSAdded MariaDB 10.1.8.
IN_TRANSAdded MariaDB 10.1.8.
AUTOCOMMITAdded MariaDB 10.1.8.
PACKET_NUMBERAdded MariaDB 10.1.8.
HITSIncremented each time the query cache is hit. Added MariaDB 10.3.2.

For example:

SELECT * FROM information_schema.QUERY_CACHE_INFO;
+------------------+-----------------+---------------------+--------------------+-------------------------+
| STATEMENT_SCHEMA | STATEMENT_TEXT  | RESULT_BLOCKS_COUNT | RESULT_BLOCKS_SIZE | RESULT_BLOCKS_SIZE_USED |
+------------------+-----------------+---------------------+--------------------+-------------------------+
...
| test             | SELECT * FROM a |                   1 |                512 |                     143 |
| test             | select * FROM a |                   1 |                512 |                     143 |
...
+------------------+-----------------+---------------------+--------------------+-------------------------

1.1.1.2.9.1.1.36 Information Schema QUERY_RESPONSE_TIME Table

Description

The Information Schema QUERY_RESPONSE_TIME table contains information about queries that take a long time to execute . It is only available if the QUERY_RESPONSE_TIME plugin has been installed.

It contains the following columns:

ColumnDescription
TIMETime interval
COUNTCount of queries falling into the time interval
TOTALTotal execution time of all queries for this interval

See QUERY_RESPONSE_TIME plugin for a full description.

The table is not a standard Information Schema table, and is a MariaDB extension.

SHOW QUERY_RESPONSE_TIME is available from MariaDB 10.1.1 as an alternative for retrieving the data.

Example

SELECT * FROM information_schema.QUERY_RESPONSE_TIME;
+----------------+-------+----------------+
| TIME           | COUNT | TOTAL          |
+----------------+-------+----------------+
|       0.000001 |     0 |       0.000000 |
|       0.000010 |    17 |       0.000094 |
|       0.000100 |  4301         0.236555 |
|       0.001000 |  1499 |       0.824450 |
|       0.010000 | 14851 |      81.680502 |
|       0.100000 |  8066 |     443.635693 |
|       1.000000 |     0 |       0.000000 |
|      10.000000 |     0 |       0.000000 |
|     100.000000 |     1 |      55.937094 |
|    1000.000000 |     0 |       0.000000 |
|   10000.000000 |     0 |       0.000000 |
|  100000.000000 |     0 |       0.000000 |
| 1000000.000000 |     0 |       0.000000 |
| TOO LONG       |     0 | TOO LONG       |
+----------------+-------+----------------+

1.1.1.2.9.1.1.37 Information Schema REFERENTIAL_CONSTRAINTS Table

The Information Schema REFERENTIAL_CONSTRAINTS table contains information about foreign keys. The single columns are listed in the KEY_COLUMN_USAGE table.

It has the following columns:

ColumnDescription
CONSTRAINT_CATALOGAlways def.
CONSTRAINT_SCHEMADatabase name, together with CONSTRAINT_NAME identifies the foreign key.
CONSTRAINT_NAMEForeign key name, together with CONSTRAINT_SCHEMA identifies the foreign key.
UNIQUE_CONSTRAINT_CATALOGAlways def.
UNIQUE_CONSTRAINT_SCHEMADatabase name, together with UNIQUE_CONSTRAINT_NAME and REFERENCED_TABLE_NAME identifies the referenced key.
UNIQUE_CONSTRAINT_NAMEReferenced key name, together with UNIQUE_CONSTRAINT_SCHEMA and REFERENCED_TABLE_NAME identifies the referenced key.
MATCH_OPTIONAlways NONE.
UPDATE_RULEThe Update Rule; one of CASCADE, SET NULL, SET DEFAULT, RESTRICT, NO ACTION.
DELETE_RULEThe Delete Rule; one of CASCADE, SET NULL, SET DEFAULT, RESTRICT, NO ACTION.
TABLE_NAMETable name from the TABLE_CONSTRAINTS table.
REFERENCED_TABLE_NAMEReferenced key table name, together with UNIQUE_CONSTRAINT_SCHEMA and UNIQUE_CONSTRAINT_NAME identifies the referenced key.

1.1.1.2.9.1.1.38 Information Schema ROUTINES Table

The Information Schema ROUTINES table stores information about stored procedures and stored functions.

It contains the following columns:

ColumnDescription
SPECIFIC_NAME
ROUTINE_CATALOGAlways def.
ROUTINE_SCHEMADatabase name associated with the routine.
ROUTINE_NAMEName of the routine.
ROUTINE_TYPEWhether the routine is a PROCEDURE or a FUNCTION.
DATA_TYPEThe return value's data type (for stored functions).
CHARACTER_MAXIMUM_LENGTHMaximum length.
CHARACTER_OCTET_LENGTHSame as the CHARACTER_MAXIMUM_LENGTH except for multi-byte character sets.
NUMERIC_PRECISIONFor numeric types, the precision (number of significant digits) for the column. NULL if not a numeric field.
NUMERIC_SCALEFor numeric types, the scale (significant digits to the right of the decimal point). NULL if not a numeric field.
DATETIME_PRECISIONFractional-seconds precision, or NULL if not a time data type.
CHARACTER_SET_NAMECharacter set if a non-binary string data type, otherwise NULL.
COLLATION_NAMECollation if a non-binary string data type, otherwise NULL.
DATA_TYPEThe column's data type.
ROUTINE_BODYAlways SQL.
ROUTINE_DEFINITIONDefinition of the routine.
EXTERNAL_NAMEAlways NULL.
EXTERNAL_LANGUAGEAlways SQL.
PARAMETER_STYLEAlways SQL.
IS_DETERMINISTICWhether the routine is deterministic (can produce only one result for a given list of parameters) or not.
SQL_DATA_ACCESSOne of READS SQL DATA, MODIFIES SQL DATA, CONTAINS SQL, or NO SQL.
SQL_PATHAlways NULL.
SECURITY_TYPEINVOKER or DEFINER. Indicates which user's privileges apply to this routine.
CREATEDDate and time the routine was created.
LAST_ALTEREDDate and time the routine was last changed.
SQL_MODEThe SQL_MODE at the time the routine was created.
ROUTINE_COMMENTComment associated with the routine.
DEFINERIf the SECURITY_TYPE is DEFINER, this value indicates which user defined this routine.
CHARACTER_SET_CLIENTThe character set used by the client that created the routine.
COLLATION_CONNECTIONThe collation (and character set) used by the connection that created the routine.
DATABASE_COLLATIONThe default collation (and character set) for the database, at the time the routine was created.

It provides information similar to, but more complete, than the SHOW PROCEDURE STATUS and SHOW FUNCTION STATUS statements.

For information about the parameters accepted by the routine, you can query the information_schema.PARAMETERS table.

See also

1.1.1.2.9.1.1.39 Information Schema SCHEMA_PRIVILEGES Table

The Information Schema SCHEMA_PRIVILEGES table contains information about database privileges.

It contains the following columns:

ColumnDescription
GRANTEEAccount granted the privilege in the format user_name@host_name.
TABLE_CATALOGAlways def
TABLE_SCHEMADatabase name.
PRIVILEGE_TYPEThe granted privilege.
IS_GRANTABLEWhether the privilege can be granted.

The same information in a different format can be found in the mysql.db table.

1.1.1.2.9.1.1.40 Information Schema SCHEMATA Table

The Information Schema SCHEMATA table stores information about databases on the server.

It contains the following columns:

ColumnDescription
CATALOG_NAMEAlways def.
SCHEMA_NAMEDatabase name.
DEFAULT_CHARACTER_SET_NAMEDefault character set for the database.
DEFAULT_COLLATION_NAMEDefault collation.
SQL_PATHAlways NULL.
SCHEMA_COMMENTDatabase comment. From MariaDB 10.5.0.

Example

SELECT * FROM INFORMATION_SCHEMA.SCHEMATA\G
*************************** 1. row ***************************
              CATALOG_NAME: def
               SCHEMA_NAME: information_schema
DEFAULT_CHARACTER_SET_NAME: utf8
    DEFAULT_COLLATION_NAME: utf8_general_ci
                  SQL_PATH: NULL
*************************** 2. row ***************************
              CATALOG_NAME: def
               SCHEMA_NAME: mysql
DEFAULT_CHARACTER_SET_NAME: latin1
    DEFAULT_COLLATION_NAME: latin1_swedish_ci
                  SQL_PATH: NULL
*************************** 3. row ***************************
              CATALOG_NAME: def
               SCHEMA_NAME: performance_schema
DEFAULT_CHARACTER_SET_NAME: utf8
    DEFAULT_COLLATION_NAME: utf8_general_ci
                  SQL_PATH: NULL
*************************** 4. row ***************************
              CATALOG_NAME: def
               SCHEMA_NAME: test
DEFAULT_CHARACTER_SET_NAME: latin1
    DEFAULT_COLLATION_NAME: latin1_swedish_ci
                  SQL_PATH: NULL
...

From MariaDB 10.5.0:

SELECT * FROM INFORMATION_SCHEMA.SCHEMATA\G
...
*************************** 2. row ***************************
              CATALOG_NAME: def
               SCHEMA_NAME: presentations
DEFAULT_CHARACTER_SET_NAME: latin1
    DEFAULT_COLLATION_NAME: latin1_swedish_ci
                  SQL_PATH: NULL
            SCHEMA_COMMENT: Presentations for conferences
...

See Also

1.1.1.2.9.1.1.41 Information Schema SPATIAL_REF_SYS Table

MariaDB starting with 10.1.2

The SPATIAL_REF_SYS table was introduced in MariaDB 10.1.2

Description

The Information Schema SPATIAL_REF_SYS table stores information on each spatial reference system used in the database.

It contains the following columns:

ColumnTypeNullDescription
SRIDsmallint(5)NOAn integer value that uniquely identifies each Spatial Reference System within a database.
AUTH_NAMEvarchar(512)NOThe name of the standard or standards body that is being cited for this reference system.
AUTH_SRIDsmallint(5)NOThe numeric ID of the coordinate system in the above authority's catalog.
SRTEXTvarchar(2048)NOThe Well-known Text Representation of the Spatial Reference System.

Note: See MDEV-7540.

See also

1.1.1.2.9.1.1.42 Information Schema SPIDER_ALLOC_MEM Table

The Information Schema SPIDER_ALLOC_MEM table is installed along with the Spider storage engine. It shows information about Spider's memory usage.

It contains the following columns:

ColumnDescription
ID
FUNC_NAME
FILE_NAME
LINE_NO
TOTAL_ALLOC_MEM
CURRENT_ALLOC_MEM
ALLOC_MEM_COUNT
FREE_MEM_COUNT

1.1.1.2.9.1.1.43 Information Schema SPIDER_WRAPPER_PROTOCOLS Table

MariaDB starting with 10.5.4

The Information Schema SPIDER_WRAPPER_PROTOCOLS table is installed along with the Spider storage engine from MariaDB 10.5.4.

It contains the following columns:

ColumnTypeDescription
WRAPPER_NAMEvarchar(64)
WRAPPER_VERSIONvarchar(20)
WRAPPER_DESCRIPTIONlongtext
WRAPPER_MATURITYvarchar(12)

1.1.1.2.9.1.1.44 Information Schema SQL_FUNCTIONS Table

MariaDB starting with 10.6.3

The SQL_FUNCTIONS table was added in MariaDB 10.6.3.

Description

The Information Schema SQL_FUNCTIONS table contains the list of MariaDB functions.

It contains a single column:

ColumnDescription
FUNCTIONFunction name

The table is not a standard Information Schema table, and is a MariaDB extension.

Example

SELECT * FROM INFORMATION_SCHEMA.SQL_FUNCTIONS;
+---------------------------+
| FUNCTION                  |
+---------------------------+
| ADDDATE                   |
| ADD_MONTHS                |
| BIT_AND                   |
| BIT_OR                    |
| BIT_XOR                   |
| CAST                      |
| COUNT                     |
| CUME_DIST                 |
| CURDATE                   |
| CURTIME                   |
| DATE_ADD                  |
| DATE_SUB                  |
| DATE_FORMAT               |
| DECODE                    |
| DENSE_RANK                |
| EXTRACT                   |
| FIRST_VALUE               |
| GROUP_CONCAT              |
| JSON_ARRAYAGG             |
| JSON_OBJECTAGG            |
| LAG                       |
| LEAD                      |
| MAX                       |
| MEDIAN                    |
| MID                       |
| MIN                       |
| NOW                       |
| NTH_VALUE                 |
| NTILE                     |
| POSITION                  |
| PERCENT_RANK              |
| PERCENTILE_CONT           |
| PERCENTILE_DISC           |
| RANK                      |
| ROW_NUMBER                |
| SESSION_USER              |
| STD                       |
| STDDEV                    |
| STDDEV_POP                |
| STDDEV_SAMP               |
| SUBDATE                   |
| SUBSTR                    |
| SUBSTRING                 |
| SUM                       |
| SYSTEM_USER               |
| TRIM                      |
| TRIM_ORACLE               |
| VARIANCE                  |
| VAR_POP                   |
| VAR_SAMP                  |
| ABS                       |
| ACOS                      |
| ADDTIME                   |
| AES_DECRYPT               |
| AES_ENCRYPT               |
| ASIN                      |
| ATAN                      |
| ATAN2                     |
| BENCHMARK                 |
| BIN                       |
| BINLOG_GTID_POS           |
| BIT_COUNT                 |
| BIT_LENGTH                |
| CEIL                      |
| CEILING                   |
| CHARACTER_LENGTH          |
| CHAR_LENGTH               |
| CHR                       |
| COERCIBILITY              |
| COLUMN_CHECK              |
| COLUMN_EXISTS             |
| COLUMN_LIST               |
| COLUMN_JSON               |
| COMPRESS                  |
| CONCAT                    |
| CONCAT_OPERATOR_ORACLE    |
| CONCAT_WS                 |
| CONNECTION_ID             |
| CONV                      |
| CONVERT_TZ                |
| COS                       |
| COT                       |
| CRC32                     |
| DATEDIFF                  |
| DAYNAME                   |
| DAYOFMONTH                |
| DAYOFWEEK                 |
| DAYOFYEAR                 |
| DEGREES                   |
| DECODE_HISTOGRAM          |
| DECODE_ORACLE             |
| DES_DECRYPT               |
| DES_ENCRYPT               |
| ELT                       |
| ENCODE                    |
| ENCRYPT                   |
| EXP                       |
| EXPORT_SET                |
| EXTRACTVALUE              |
| FIELD                     |
| FIND_IN_SET               |
| FLOOR                     |
| FORMAT                    |
| FOUND_ROWS                |
| FROM_BASE64               |
| FROM_DAYS                 |
| FROM_UNIXTIME             |
| GET_LOCK                  |
| GREATEST                  |
| HEX                       |
| IFNULL                    |
| INSTR                     |
| ISNULL                    |
| IS_FREE_LOCK              |
| IS_USED_LOCK              |
| JSON_ARRAY                |
| JSON_ARRAY_APPEND         |
| JSON_ARRAY_INSERT         |
| JSON_COMPACT              |
| JSON_CONTAINS             |
| JSON_CONTAINS_PATH        |
| JSON_DEPTH                |
| JSON_DETAILED             |
| JSON_EXISTS               |
| JSON_EXTRACT              |
| JSON_INSERT               |
| JSON_KEYS                 |
| JSON_LENGTH               |
| JSON_LOOSE                |
| JSON_MERGE                |
| JSON_MERGE_PATCH          |
| JSON_MERGE_PRESERVE       |
| JSON_QUERY                |
| JSON_QUOTE                |
| JSON_OBJECT               |
| JSON_REMOVE               |
| JSON_REPLACE              |
| JSON_SET                  |
| JSON_SEARCH               |
| JSON_TYPE                 |
| JSON_UNQUOTE              |
| JSON_VALID                |
| JSON_VALUE                |
| LAST_DAY                  |
| LAST_INSERT_ID            |
| LCASE                     |
| LEAST                     |
| LENGTH                    |
| LENGTHB                   |
| LN                        |
| LOAD_FILE                 |
| LOCATE                    |
| LOG                       |
| LOG10                     |
| LOG2                      |
| LOWER                     |
| LPAD                      |
| LPAD_ORACLE               |
| LTRIM                     |
| LTRIM_ORACLE              |
| MAKEDATE                  |
| MAKETIME                  |
| MAKE_SET                  |
| MASTER_GTID_WAIT          |
| MASTER_POS_WAIT           |
| MD5                       |
| MONTHNAME                 |
| NAME_CONST                |
| NVL                       |
| NVL2                      |
| NULLIF                    |
| OCT                       |
| OCTET_LENGTH              |
| ORD                       |
| PERIOD_ADD                |
| PERIOD_DIFF               |
| PI                        |
| POW                       |
| POWER                     |
| QUOTE                     |
| REGEXP_INSTR              |
| REGEXP_REPLACE            |
| REGEXP_SUBSTR             |
| RADIANS                   |
| RAND                      |
| RELEASE_ALL_LOCKS         |
| RELEASE_LOCK              |
| REPLACE_ORACLE            |
| REVERSE                   |
| ROUND                     |
| RPAD                      |
| RPAD_ORACLE               |
| RTRIM                     |
| RTRIM_ORACLE              |
| SEC_TO_TIME               |
| SHA                       |
| SHA1                      |
| SHA2                      |
| SIGN                      |
| SIN                       |
| SLEEP                     |
| SOUNDEX                   |
| SPACE                     |
| SQRT                      |
| STRCMP                    |
| STR_TO_DATE               |
| SUBSTR_ORACLE             |
| SUBSTRING_INDEX           |
| SUBTIME                   |
| SYS_GUID                  |
| TAN                       |
| TIMEDIFF                  |
| TIME_FORMAT               |
| TIME_TO_SEC               |
| TO_BASE64                 |
| TO_CHAR                   |
| TO_DAYS                   |
| TO_SECONDS                |
| UCASE                     |
| UNCOMPRESS                |
| UNCOMPRESSED_LENGTH       |
| UNHEX                     |
| UNIX_TIMESTAMP            |
| UPDATEXML                 |
| UPPER                     |
| UUID                      |
| UUID_SHORT                |
| VERSION                   |
| WEEKDAY                   |
| WEEKOFYEAR                |
| WSREP_LAST_WRITTEN_GTID   |
| WSREP_LAST_SEEN_GTID      |
| WSREP_SYNC_WAIT_UPTO_GTID |
| YEARWEEK                  |
+---------------------------+
234 rows in set (0.001 sec)

See Also

1.1.1.2.9.1.1.45 Information Schema STATISTICS Table

The Information Schema STATISTICS table provides information about table indexes.

It contains the following columns:

ColumnDescription
TABLE_CATALOGAlways def.
TABLE_SCHEMADatabase name.
TABLE_NAMETable name.
NON_UNIQUE1 if the index can have duplicates, 0 if not.
INDEX_SCHEMADatabase name.
INDEX_NAMEIndex name. The primary key is always named PRIMARY.
SEQ_IN_INDEXThe column sequence number, starting at 1.
COLUMN_NAMEColumn name.
COLLATIONA for sorted in ascending order, or NULL for unsorted.
CARDINALITYEstimate of the number of unique values stored in the index based on statistics stored as integers. Higher cardinalities usually mean a greater chance of the index being used in a join. Updated by the ANALYZE TABLE statement or myisamchk -a.
SUB_PARTNULL if the whole column is indexed, or the number of indexed characters if partly indexed.
PACKEDNULL if not packed, otherwise how the index is packed.
NULLABLEYES if the column may contain NULLs, empty string if not.
INDEX_TYPEIndex type, one of BTREE, RTREE, HASH or FULLTEXT. See Storage Engine Index Types.
COMMENTIndex comments from the CREATE INDEX statement.
IGNOREDWhether or not an index will be ignored by the optimizer. See Ignored Indexes. From MariaDB 10.6.0.

The SHOW INDEX statement produces similar output.

Example

SELECT * FROM INFORMATION_SCHEMA.STATISTICS\G
...
*************************** 85. row ***************************
TABLE_CATALOG: def
 TABLE_SCHEMA: test
   TABLE_NAME: table1
   NON_UNIQUE: 1
 INDEX_SCHEMA: test
   INDEX_NAME: col2
 SEQ_IN_INDEX: 1
  COLUMN_NAME: col2
    COLLATION: A
  CARDINALITY: 6
     SUB_PART: NULL
       PACKED: NULL
     NULLABLE: 
   INDEX_TYPE: BTREE
      COMMENT: 
INDEX_COMMENT:
...

1.1.1.2.9.1.1.46 Information Schema SYSTEM_VARIABLES Table

MariaDB starting with 10.1.1

The information_schema.SYSTEM_VARIABLES table was introduced in MariaDB 10.1.1

The Information Schema SYSTEM_VARIABLES table shows current values and various metadata of all system variables.

It contains the following columns:

ColumnDescription
VARIABLE_NAMESystem variable name.
SESSION_VALUESession value of the variable or NULL if the variable only has a global scope.
GLOBAL_VALUEGlobal value of the variable or NULL if the variable only has a session scope.
GLOBAL_VALUE_ORIGINHow the global value was set — a compile-time default, auto-configured by the server, configuration file (or a command line), with the SQL statement.
DEFAULT_VALUECompile-time default value of the variable.
VARIABLE_SCOPEGlobal, session, or session-only.
VARIABLE_TYPEData type of the variable value.
VARIABLE_COMMENTHelp text, usually shown in mysqld --help --verbose.
NUMERIC_MIN_VALUEFor numeric variables — minimal allowed value.
NUMERIC_MAX_VALUEFor numeric variables — maximal allowed value.
NUMERIC_BLOCK_SIZEFor numeric variables — a valid value must be a multiple of the "block size".
ENUM_VALUE_LISTFor ENUM, SET, and FLAGSET variables — the list of recognized values.
READ_ONLYWhether a variable can be set with the SQL statement. Note that many "read only" variables can still be set on the command line.
COMMAND_LINE_ARGUMENTWhether an argument is required when setting the variable on the command line. NULL when a variable can not be set on the command line.
GLOBAL_VALUE_PATHWhich config file the variable got its value from. NULL if not set in any config file. Added in MariaDB 10.5.0.

Example

SELECT * FROM information_schema.SYSTEM_VARIABLES 
  WHERE VARIABLE_NAME='JOIN_BUFFER_SIZE'\G
*************************** 1. row *****************************
        VARIABLE_NAME: JOIN_BUFFER_SIZE
        SESSION_VALUE: 131072
         GLOBAL_VALUE: 131072
  GLOBAL_VALUE_ORIGIN: COMPILE-TIME
        DEFAULT_VALUE: 131072
       VARIABLE_SCOPE: SESSION
        VARIABLE_TYPE: BIGINT UNSIGNED
     VARIABLE_COMMENT: The size of the buffer that is used for joins
    NUMERIC_MIN_VALUE: 128
    NUMERIC_MAX_VALUE: 18446744073709551615
   NUMERIC_BLOCK_SIZE: 128
      ENUM_VALUE_LIST: NULL
            READ_ONLY: NO
COMMAND_LINE_ARGUMENT: REQUIRED

1.1.1.2.9.1.1.47 Information Schema TABLE_CONSTRAINTS Table

The Information Schema TABLE_CONSTRAINTS table contains information about tables that have constraints.

It has the following columns:

ColumnDescription
CONSTRAINT_CATALOGAlways def.
CONSTRAINT_SCHEMADatabase name containing the constraint.
CONSTRAINT_NAMEConstraint name.
TABLE_SCHEMADatabase name.
TABLE_NAMETable name.
CONSTRAINT_TYPEType of constraint; one of UNIQUE, PRIMARY KEY, FOREIGN KEY or CHECK.

The REFERENTIAL_CONSTRAINTS table has more information about foreign keys.

1.1.1.2.9.1.1.48 Information Schema TABLE_PRIVILEGES Table

The Information Schema TABLE_PRIVILEGES table contains table privilege information derived from the mysql.tables_priv grant table.

It has the following columns:

ColumnDescription
GRANTEEIn the format user_name@host_name.
TABLE_CATALOGAlways def.
TABLE_SCHEMADatabase name.
TABLE_NAMETable name.
PRIVILEGE_TYPEOne of SELECT, INSERT, UPDATE, REFERENCES, ALTER, INDEX, DROP or CREATE VIEW.
IS_GRANTABLEWhether the user has the GRANT OPTION for this privilege.

Similar information can be accessed with the SHOW GRANTS statement. See the GRANT article for more about privileges.

For a description of the privileges that are shown in this table, see table privileges.

1.1.1.2.9.1.1.49 Information Schema TABLE_STATISTICS Table

The Information Schema TABLE_STATISTICS table shows statistics on table usage.

This is part of the User Statistics feature, which is not enabled by default.

It contains the following columns:

FieldTypeNotes
TABLE_SCHEMAvarchar(192)The schema (database) name.
TABLE_NAMEvarchar(192)The table name.
ROWS_READint(21)The number of rows read from the table.
ROWS_CHANGEDint(21)The number of rows changed in the table.
ROWS_CHANGED_X_INDEXESint(21)The number of rows changed in the table, multiplied by the number of indexes changed.

Example

SELECT * FROM INFORMATION_SCHEMA.TABLE_STATISTICS WHERE TABLE_NAME='user';
+--------------+------------+-----------+--------------+------------------------+
| TABLE_SCHEMA | TABLE_NAME | ROWS_READ | ROWS_CHANGED | ROWS_CHANGED_X_INDEXES |
+--------------+------------+-----------+--------------+------------------------+
| mysql        | user       |         5 |            2 |                      2 |
+--------------+------------+-----------+--------------+------------------------+

1.1.1.2.9.1.1.50 Information Schema TABLES Table

Contents

  1. Examples
    1. View Tables in Order of Size
  2. See Also

The Information Schema table shows information about the various non-TEMPORARY tables (except tables from the Information Schema database) and views on the server.

It contains the following columns:

ColumnDescription
TABLE_CATALOGAlways def.
TABLE_SCHEMADatabase name.
TABLE_NAMETable name.
TABLE_TYPEOne of BASE TABLE for a regular table, VIEW for a view, SYSTEM VIEW for Information Schema tables, SYSTEM VERSIONED for system-versioned tables or SEQUENCE for sequences.
ENGINEStorage Engine.
VERSIONVersion number from the table's .frm file
ROW_FORMATRow format (see InnoDB, Aria and MyISAM row formats).
TABLE_ROWSNumber of rows in the table. Some engines, such as XtraDB and InnoDB may store an estimate.
AVG_ROW_LENGTHAverage row length in the table.
DATA_LENGTHFor InnoDB/XtraDB, the index size, in pages, multiplied by the page size. For Aria and MyISAM, length of the data file, in bytes. For MEMORY, the approximate allocated memory.
MAX_DATA_LENGTHMaximum length of the data file, ie the total number of bytes that could be stored in the table. Not used in XtraDB and InnoDB.
INDEX_LENGTHLength of the index file.
DATA_FREEBytes allocated but unused. For InnoDB tables in a shared tablespace, the free space of the shared tablespace with small safety margin. An estimate in the case of partitioned tables - see the PARTITIONS table.
AUTO_INCREMENTNext AUTO_INCREMENT value.
CREATE_TIMETime the table was created.
UPDATE_TIMETime the table was last updated. On Windows, the timestamp is not updated on update, so MyISAM values will be inaccurate. In InnoDB, if shared tablespaces are used, will be NULL, while buffering can also delay the update, so the value will differ from the actual time of the last UPDATE, INSERT or DELETE.
CHECK_TIMETime the table was last checked. Not kept by all storage engines, in which case will be NULL.
TABLE_COLLATIONCharacter set and collation.
CHECKSUMLive checksum value, if any.
CREATE_OPTIONSExtra CREATE TABLE options.
TABLE_COMMENTTable comment provided when MariaDB created the table.
MAX_INDEX_LENGTHMaximum index length (supported by MyISAM and Aria tables). Added in MariaDB 10.3.5.
TEMPORARYPlaceholder to signal that a table is a temporary table. Currently always "N", except "Y" for generated information_schema tables and NULL for views. Added in MariaDB 10.3.5.

Although the table is standard in the Information Schema, all but TABLE_CATALOG, TABLE_SCHEMA, TABLE_NAME, TABLE_TYPE, ENGINE and VERSION are MySQL and MariaDB extensions.

SHOW TABLES lists all tables in a database.

Examples

From MariaDB 10.3.5:

SELECT * FROM information_schema.tables WHERE table_schema='test'\G
*************************** 1. row ***************************
   TABLE_CATALOG: def
    TABLE_SCHEMA: test
      TABLE_NAME: xx5
      TABLE_TYPE: BASE TABLE
          ENGINE: InnoDB
         VERSION: 10
      ROW_FORMAT: Dynamic
      TABLE_ROWS: 0
  AVG_ROW_LENGTH: 0
     DATA_LENGTH: 16384
 MAX_DATA_LENGTH: 0
    INDEX_LENGTH: 0
       DATA_FREE: 0
  AUTO_INCREMENT: NULL
     CREATE_TIME: 2020-11-18 15:57:10
     UPDATE_TIME: NULL
      CHECK_TIME: NULL
 TABLE_COLLATION: latin1_swedish_ci
        CHECKSUM: NULL
  CREATE_OPTIONS: 
   TABLE_COMMENT: 
MAX_INDEX_LENGTH: 0
       TEMPORARY: N
*************************** 2. row ***************************
   TABLE_CATALOG: def
    TABLE_SCHEMA: test
      TABLE_NAME: xx4
      TABLE_TYPE: BASE TABLE
          ENGINE: MyISAM
         VERSION: 10
      ROW_FORMAT: Fixed
      TABLE_ROWS: 0
  AVG_ROW_LENGTH: 0
     DATA_LENGTH: 0
 MAX_DATA_LENGTH: 1970324836974591
    INDEX_LENGTH: 1024
       DATA_FREE: 0
  AUTO_INCREMENT: NULL
     CREATE_TIME: 2020-11-18 15:56:57
     UPDATE_TIME: 2020-11-18 15:56:57
      CHECK_TIME: NULL
 TABLE_COLLATION: latin1_swedish_ci
        CHECKSUM: NULL
  CREATE_OPTIONS: 
   TABLE_COMMENT: 
MAX_INDEX_LENGTH: 17179868160
       TEMPORARY: N
...

Example with temporary = 'y', from MariaDB 10.3.5:

SELECT * FROM information_schema.tables WHERE temporary='y'\G
 *************************** 1. row ***************************
   TABLE_CATALOG: def
    TABLE_SCHEMA: information_schema
      TABLE_NAME: INNODB_FT_DELETED
      TABLE_TYPE: SYSTEM VIEW
          ENGINE: MEMORY
         VERSION: 11
      ROW_FORMAT: Fixed
      TABLE_ROWS: NULL
  AVG_ROW_LENGTH: 9
     DATA_LENGTH: 0
 MAX_DATA_LENGTH: 9437184
    INDEX_LENGTH: 0
       DATA_FREE: 0
  AUTO_INCREMENT: NULL
     CREATE_TIME: 2020-11-17 21:54:02
     UPDATE_TIME: NULL
      CHECK_TIME: NULL
 TABLE_COLLATION: utf8_general_ci
        CHECKSUM: NULL
  CREATE_OPTIONS: max_rows=1864135
   TABLE_COMMENT: 
MAX_INDEX_LENGTH: 0
       TEMPORARY: Y
...

View Tables in Order of Size

Returns a list of all tables in the database, ordered by size:

SELECT table_schema as `DB`, table_name AS `Table`, 
  ROUND(((data_length + index_length) / 1024 / 1024), 2) `Size (MB)` 
  FROM information_schema.TABLES 
  ORDER BY (data_length + index_length) DESC;

+--------------------+---------------------------------------+-----------+
| DB                 | Table                                 | Size (MB) |
+--------------------+---------------------------------------+-----------+
| wordpress          | wp_simple_history_contexts            |      7.05 |
| wordpress          | wp_posts                              |      6.59 |
| wordpress          | wp_simple_history                     |      3.05 |
| wordpress          | wp_comments                           |      2.73 |
| wordpress          | wp_commentmeta                        |      2.47 |
| wordpress          | wp_simple_login_log                   |      2.03 |
...

See Also

1.1.1.2.9.1.1.51 Information Schema TABLESPACES Table

The Information Schema TABLESPACES table contains information about active tablespaces..

The table is a MariaDB and MySQL extension, and does not include information about InnoDB tablespaces.

ColumnDescription
TABLESPACE_NAME
ENGINE
TABLESPACE_TYPE
LOGFILE_GROUP_NAME
EXTENT_SIZE
AUTOEXTEND_SIZE
MAXIMUM_SIZE
NODEGROUP_ID
TABLESPACE_COMMENT

1.1.1.2.9.1.1.52 Information Schema THREAD_POOL_GROUPS Table

MariaDB starting with 10.5

The Information Schema THREAD_POOL_GROUPS table was introduced in MariaDB 10.5.0.

The table provides information about thread pool groups, and contains the following columns:

ColumnDescription
GROUP_ID
CONNECTIONS
THREADS
ACTIVE_THREADS
STANDBY_THREADS
QUEUE_LENGTH
HAS_LISTENER
IS_STALLED

Setting thread_pool_dedicated_listener will give each group its own dedicated listener, and the listener thread will not pick up work items. As a result, the actual queue size in the table will be more exact, since IO requests are immediately dequeued from poll, without delay.

1.1.1.2.9.1.1.53 Information Schema THREAD_POOL_STATS Table

MariaDB starting with 10.5

The Information Schema THREAD_POOL_STATS table was introduced in MariaDB 10.5.0.

The table provides performance counter information for the thread pool, and contains the following columns:

ColumnDescription
GROUP_ID
THREAD_CREATIONS
THREAD_CREATIONS_DUE_TO_STALL
WAKES
WAKES_DUE_TO_STALL
THROTTLES
STALLS
POLLS_BY_LISTENER
POLLS_BY_WORKER
DEQUEUES_BY_LISTENER
DEQUEUES_BY_WORKER

1.1.1.2.9.1.1.54 Information Schema THREAD_POOL_WAITS Table

MariaDB starting with 10.5

The Information Schema THREAD_POOL_WAITS table was introduced in MariaDB 10.5.0.

The table provides wait counters for the thread pool, and contains the following columns:

ColumnDescription
REASON
COUNT

1.1.1.2.9.1.1.55 Information Schema TRIGGERS Table

Contents

  1. See also

The Information Schema TRIGGERS table contains information about triggers.

It has the following columns:

ColumnDescription
TRIGGER_CATALOGAlways def.
TRIGGER_SCHEMADatabase name in which the trigger occurs.
TRIGGER_NAMEName of the trigger.
EVENT_MANIPULATIONThe event that activates the trigger. One of INSERT, UPDATE or 'DELETE.
EVENT_OBJECT_CATALOGAlways def.
EVENT_OBJECT_SCHEMADatabase name on which the trigger acts.
EVENT_OBJECT_TABLETable name on which the trigger acts.
ACTION_ORDERIndicates the order that the action will be performed in (of the list of a table's triggers with identical EVENT_MANIPULATION and ACTION_TIMING values). Before MariaDB 10.2.3 introduced the FOLLOWS and PRECEDES clauses, always 0
ACTION_CONDITIONNULL
ACTION_STATEMENTTrigger body, UTF-8 encoded.
ACTION_ORIENTATIONAlways ROW.
ACTION_TIMINGWhether the trigger acts BEFORE or AFTER the event that triggers it.
ACTION_REFERENCE_OLD_TABLEAlways NULL.
ACTION_REFERENCE_NEW_TABLEAlways NULL.
ACTION_REFERENCE_OLD_ROWAlways OLD.
ACTION_REFERENCE_NEW_ROWAlways NEW.
CREATEDAlways NULL.
SQL_MODEThe SQL_MODE when the trigger was created, and which it uses for execution.
DEFINERThe account that created the trigger, in the form user_name@host_name
CHARACTER_SET_CLIENTThe client character set when the trigger was created, from the session value of the character_set_client system variable.
COLLATION_CONNECTIONThe client collation when the trigger was created, from the session value of the collation_connection system variable.
DATABASE_COLLATIONCollation of the associated database.

Queries to the TRIGGERS table will return information only for databases and tables for which you have the TRIGGER privilege. Similar information is returned by the SHOW TRIGGERS statement.

See also

1.1.1.2.9.1.1.56 Information Schema USER_PRIVILEGES Table

The Information Schema USER_PRIVILEGES table contains global user privilege information derived from the mysql.user grant table.

It contains the following columns:

ColumnDescription
GRANTEEIn the format user_name@host_name.
TABLE_CATALOGAlways def.
PRIVILEGE_TYPEThe specific privilege, for example SELECT, INSERT, UPDATE or REFERENCES.
IS_GRANTABLEWhether the user has the GRANT OPTION for this privilege.

Similar information can be accessed with the SHOW GRANTS statement. See the GRANT article for more about privileges.

This information is also stored in the user table, in the mysql system database.

1.1.1.2.9.1.1.57 Information Schema USER_STATISTICS Table

The Information Schema USER_STATISTICS table holds statistics about user activity. This is part of the User Statistics feature, which is not enabled by default.

You can use this table to find out such things as which user is causing the most load and which users are being abusive. You can also use this table to measure how close to capacity the server may be.

It contains the following columns:

FieldTypeNotes
USERvarchar(48)The username. The value '#mysql_system_user#' appears when there is no username (such as for the slave SQL thread).
TOTAL_CONNECTIONSint(21)The number of connections created for this user.
CONCURRENT_CONNECTIONSint(21)The number of concurrent connections for this user.
CONNECTED_TIMEint(21)The cumulative number of seconds elapsed while there were connections from this user.
BUSY_TIMEdoubleThe cumulative number of seconds there was activity on connections from this user.
CPU_TIMEdoubleThe cumulative CPU time elapsed while servicing this user's connections.
BYTES_RECEIVEDint(21)The number of bytes received from this user's connections.
BYTES_SENTint(21)The number of bytes sent to this user's connections.
BINLOG_BYTES_WRITTENint(21)The number of bytes written to the binary log from this user's connections.
ROWS_READint(21)The number of rows read by this user's connections.
ROWS_SENTint(21)The number of rows sent by this user's connections.
ROWS_DELETEDint(21)The number of rows deleted by this user's connections.
ROWS_INSERTEDint(21)The number of rows inserted by this user's connections.
ROWS_UPDATEDint(21)The number of rows updated by this user's connections.
SELECT_COMMANDSint(21)The number of SELECT commands executed from this user's connections.
UPDATE_COMMANDSint(21)The number of UPDATE commands executed from this user's connections.
OTHER_COMMANDSint(21)The number of other commands executed from this user's connections.
COMMIT_TRANSACTIONSint(21)The number of COMMIT commands issued by this user's connections.
ROLLBACK_TRANSACTIONSint(21)The number of ROLLBACK commands issued by this user's connections.
DENIED_CONNECTIONSint(21)The number of connections denied to this user.
LOST_CONNECTIONSint(21)The number of this user's connections that were terminated uncleanly.
ACCESS_DENIEDint(21)The number of times this user's connections issued commands that were denied.
EMPTY_QUERIESint(21)The number of times this user's connections sent empty queries to the server.
TOTAL_SSL_CONNECTIONSint(21)The number of TLS connections created for this user. (>= MariaDB 10.1.1)
MAX_STATEMENT_TIME_EXCEEDEDint(21)The number of times a statement was aborted, because it was executed longer than its MAX_STATEMENT_TIME threshold. (>= MariaDB 10.1.1)

Example

SELECT * FROM information_schema.USER_STATISTICS\G
*************************** 1. row ***************************
                  USER: root
     TOTAL_CONNECTIONS: 1
CONCURRENT_CONNECTIONS: 0
        CONNECTED_TIME: 297
             BUSY_TIME: 0.001725
              CPU_TIME: 0.001982
        BYTES_RECEIVED: 388
            BYTES_SENT: 2327
  BINLOG_BYTES_WRITTEN: 0
             ROWS_READ: 0
             ROWS_SENT: 12
          ROWS_DELETED: 0
         ROWS_INSERTED: 13
          ROWS_UPDATED: 0
       SELECT_COMMANDS: 4
       UPDATE_COMMANDS: 0
        OTHER_COMMANDS: 3
   COMMIT_TRANSACTIONS: 0
 ROLLBACK_TRANSACTIONS: 0
    DENIED_CONNECTIONS: 0
      LOST_CONNECTIONS: 0
         ACCESS_DENIED: 0
         EMPTY_QUERIES: 1

1.1.1.2.9.1.1.58 Information Schema USER_VARIABLES Table

MariaDB 10.2.0

The USER_VARIABLES table was introduced in MariaDB 10.2.0 as part of the user_variables plugin.

Description

The USER_VARIABLES table is created when the user_variables plugin is enabled, and contains information about user-defined variables.

The table contains the following columns:

ColumnDescription
VARIABLE_NAMEVariable name.
VARIABLE_VALUEVariable value.
VARIABLE_TYPEVariable type.
CHARACTER_SET_NAMECharacter set.

Example

SELECT * FROM information_schema.USER_VARIABLES ORDER BY VARIABLE_NAME;
+---------------+----------------+---------------+--------------------+
| VARIABLE_NAME | VARIABLE_VALUE | VARIABLE_TYPE | CHARACTER_SET_NAME |
+---------------+----------------+---------------+--------------------+
| var           | 0              | INT           | utf8               |
| var2          | abc            | VARCHAR       | utf8               |
+---------------+----------------+---------------+--------------------+

1.1.1.2.9.1.1.59 Information Schema VIEWS Table

The Information Schema VIEWS table contains information about views. The SHOW VIEW privilege is required to view the table.

It has the following columns:

ColumnDescriptionAdded
TABLE_CATALOGAways def.
TABLE_SCHEMADatabase name containing the view.
TABLE_NAMEView table name.
VIEW_DEFINITIONDefinition of the view.
CHECK_OPTIONYES if the WITH CHECK_OPTION clause has been specified, NO otherwise.
IS_UPDATABLEWhether the view is updatable or not.
DEFINERAccount specified in the DEFINER clause (or the default when created).
SECURITY_TYPESQL SECURITY characteristic, either DEFINER or INVOKER.
CHARACTER_SET_CLIENTThe client character set when the view was created, from the session value of the character_set_client system variable.
COLLATION_CONNECTIONThe client collation when the view was created, from the session value of the collation_connection system variable.
ALGORITHMThe algorithm used in the view. See View Algorithms.MariaDB 10.1.3

Example

SELECT * FROM information_schema.VIEWS\G
*************************** 1. row ***************************
       TABLE_CATALOG: def
        TABLE_SCHEMA: test
          TABLE_NAME: v
     VIEW_DEFINITION: select `test`.`t`.`qty` AS `qty`,`test`.`t`.`price` AS `price`,(`test`.`t`.`qty` * `test`.`t`.`price`) AS `value` from `test`.`t`
        CHECK_OPTION: NONE
        IS_UPDATABLE: YES
             DEFINER: root@localhost
       SECURITY_TYPE: DEFINER
CHARACTER_SET_CLIENT: utf8
COLLATION_CONNECTION: utf8_general_ci
           ALGORITHM: UNDEFINED

See also

1.1.1.2.9.1.1.60 Information Schema WSREP_MEMBERSHIP Table

The WSREP_STATUS table makes Galera node cluster membership information available through the Information Schema. The same information can be returned using the SHOW WSREP_MEMBERSHIP statement. Only users with the SUPER can access information from this table.

The WSREP_MEMBERSHIP table is part of the WSREP_INFO plugin.

Example

SELECT * FROM information_schema.WSREP_MEMBERSHIP;
+-------+--------------------------------------+-------+-----------------+
| INDEX | UUID                                 | NAME  | ADDRESS         |
+-------+--------------------------------------+-------+-----------------+
|     0 | 46da96e3-6e9e-11e4-95a2-f609aa5444b3 | node1 | 10.0.2.15:16000 |
|     1 | 5f6bc72a-6e9e-11e4-84ed-57ec6780a3d3 | node2 | 10.0.2.15:16001 |
|     2 | 7473fd75-6e9e-11e4-91de-0b541ad91bd0 | node3 | 10.0.2.15:16002 |
+-------+--------------------------------------+-------+-----------------+

1.1.1.2.9.1.1.61 Information Schema WSREP_STATUS Table

The WSREP_STATUS table makes Galera node cluster status information available through the Information Schema. The same information can be returned using the SHOW WSREP_STATUS statement. Only users with the SUPER privilege can access information from this table.

The WSREP_STATUS table is part of the WSREP_INFO plugin.

Example

SELECT * FROM information_schema.WSREP_STATUS\G
*************************** 1. row ***************************
         NODE_INDEX: 0
        NODE_STATUS: Synced
     CLUSTER_STATUS: Primary
       CLUSTER_SIZE: 3
 CLUSTER_STATE_UUID: 00b0fbad-6e84-11e4-8a8b-376f19ce8ee7
CLUSTER_STATE_SEQNO: 2
    CLUSTER_CONF_ID: 3
                GAP: NO
   PROTOCOL_VERSION: 3

1.1.1.2.9.1.2 Extended SHOW

1.1.1.2.9.1.3 TIME_MS column in INFORMATION_SCHEMA.PROCESSLIST

In MariaDB, an extra column TIME_MS has been added to the INFORMATION_SCHEMA.PROCESSLIST table. This column shows the same information as the column 'TIME', but in units of milliseconds with microsecond precision (the unit and precision of the TIME column is one second).

For details about microseconds support in MariaDB, see microseconds in MariaDB.

The value displayed in the TIME and TIME_MS columns is the period of time that the given thread has been in its current state. Thus it can be used to check for example how long a thread has been executing the current query, or for how long it has been idle.

select id, time, time_ms, command, state from
   information_schema.processlist, (select sleep(2)) t;
+----+------+----------+---------+-----------+
| id | time | time_ms  | command | state     |
+----+------+----------+---------+-----------+
| 37 |    2 | 2000.493 | Query   | executing |
+----+------+----------+---------+-----------+

Note that as a difference to MySQL, in MariaDB the TIME column (and also the TIME_MS column) are not affected by any setting of @TIMESTAMP. This means that it can be reliably used also for threads that change @TIMESTAMP (such as the replication SQL thread). See also MySQL Bug #22047.

As a consequence of this, the TIME column of SHOW FULL PROCESSLIST and INFORMATION_SCHEMA.PROCESSLIST can not be used to determine if a slave is lagging behind. For this, use instead the Seconds_Behind_Master column in the output of SHOW SLAVE STATUS.

The addition of the TIME_MS column is based on the microsec_process patch, developed by Percona.

1.1.1.2.9.2 Performance Schema

The MariaDB Performance Schema is a feature for monitoring the performance of your MariaDB server.

There are 4 related questions.

1.1.1.2.9.2.1 Performance Schema Tables

Tables that are part of the MariaDB Performance Schema, a feature for monitoring the performance of MariaDB server.

1.1.1.2.9.2.1.1 List of Performance Schema Tables

Below is a list of all Performance Schema tables as well as a brief description of each of them.

TableDescription
accountsClient account connection statistics.
cond_instancesSynchronization object instances.
events_stages_currentCurrent stage events.
events_stages_historyTen most recent stage events per thread.
events_stages_history_longTen thousand most recent stage events.
events_stages_summary_by_account_by_event_nameSummarized stage events per account and event name.
events_stages_summary_by_host_by_event_nameSummarized stage events per host and event name.
events_stages_summary_by_thread_by_event_nameSummarized stage events per thread and event name.
events_stages_summary_by_user_by_event_nameSummarized stage events per user name and event name.
events_stages_summary_global_by_event_nameSummarized stage events per event name.
events_statements_currentCurrent statement events.
events_statements_historyTen most recent events per thread.
events_statements_history_longTen thousand most recent stage events.
events_statements_summary_by_account_by_event_nameSummarized statement events per account and event name.
events_statements_summary_by_digestSummarized statement events by scheme and digest.
events_statements_summary_by_host_by_event_nameSummarized statement events by host and event name.
events_statements_summary_by_program
events_statements_summary_by_thread_by_event_nameSummarized statement events by thread and event name.
events_statements_summary_by_user_by_event_nameSummarized statement events by user and event name.
events_statements_summary_global_by_event_nameSummarized statement events by event name.
events_transactions_currentCurrent transaction events for each thread.
events_transactions_historyMost recent completed transaction events for each thread.
events_transactions_history_longMost recent completed transaction events that have ended globally.
events_transactions_summary_by_account_by_event_nameTransaction events aggregated by account and event.
events_transactions_summary_by_host_by_event_nameTransaction events aggregated by host and event..
events_transactions_summary_by_thread_by_event_nameTransaction events aggregated by thread and event..
events_transactions_summary_by_user_by_event_nameTransaction events aggregated by user and event..
events_transactions_summary_global_by_event_nameTransaction events aggregated by event name.
events_waits_currentCurrent wait events.
events_waits_historyTen most recent wait events per thread.
events_waits_history_longTen thousand most recent wait events per thread.
events_waits_summary_by_account_by_event_nameSummarized wait events by account and event name.
events_waits_summary_by_host_by_event_nameSummarized wait events by host and event name.
events_waits_summary_by_instanceSummarized wait events by instance.
events_waits_summary_by_thread_by_event_nameSummarized wait events by thread and event name.
events_waits_summary_by_user_by_event_nameSummarized wait events by user and event name.
events_waits_summary_global_by_event_nameSummarized wait events by event name.
file_instancesSeen files.
file_summary_by_event_nameFile events summarized by event name.
file_summary_by_instanceFile events summarized by instance.
global_statusGlobal status variables and values.
host_cacheHost and IP information.
hostsConnections by host.
memory_summary_by_account_by_event_nameMemory usage statistics aggregated by account and event.
memory_summary_by_host_by_event_nameMemory usage statistics aggregated by host. and event.
memory_summary_by_thread_by_event_nameMemory usage statistics aggregated by thread and event..
memory_summary_by_user_by_event_nameMemory usage statistics aggregated by user and event..
memory_summary_global_by_event_nameMemory usage statistics aggregated by event.
metadata_locksMetadata locks.
mutex_instancesSeen mutexes.
objects_summary_global_by_typeObject wait events.
performance_timersAvailable event timers.
prepared_statements_instancesAggregate statistics of prepared statements.
replication_applier_configurationConfiguration settings affecting replica transactions.
replication_applier_statusGeneral transaction execution status on the replica.
replication_applier_status_by_coordinatorCoordinator thread specific information.
replication_applier_status_by_workerReplica worker thread specific information.
replication_connection_configurationRreplica's configuration settings used for connecting to the primary.
rwlock_instancesSeen read-write locks.
session_account_connect_attrsCurrent session connection attributes.
session_connect_attrsAll session connection attributes.
session_statusSession status variables and values.
setup_actorsDetails on foreground thread monitoring.
setup_consumersConsumers for which event information is stored.
setup_instrumentsInstrumented objects for which events are collected.
setup_objectsObjects to be monitored.
setup_timersCurrently selected event timers.
socket_instancesActive connections.
socket_summary_by_event_nameTimer and byte count statistics by socket instrument.
socket_summary_by_instanceTimer and byte count statistics by socket instance.
status_by_threadStatus variable info about active foreground threads.
table_io_waits_summary_by_index_usageAggregate table I/O wait events by index.
table_io_waits_summary_by_tableAggregate table I/O wait events by table.
table_lock_waits_summary_by_tableAggregate table lock wait events by table.
threadsServer thread information.
usersConnection statistics by user.

1.1.1.2.9.2.1.2 Performance Schema accounts Table

Description

Each account that connects to the server is stored as a row in the accounts table, along with current and total connections.

The table size is determined at startup by the value of the performance_schema_accounts_size system variable. If this is set to 0, account statistics will be disabled.

ColumnDescription
USERThe connection's client user name for the connection, or NULL if an internal thread.
HOSTThe connection client's host name, or NULL if an internal thread.
CURRENT_CONNECTIONSCurrent connections for the account.
TOTAL_CONNECTIONSTotal connections for the account.

The USER and HOST values shown here are the username and host used for user connections, not the patterns used to check permissions.

Example

SELECT * FROM performance_schema.accounts;
+------------------+-----------+---------------------+-------------------+
| USER             | HOST      | CURRENT_CONNECTIONS | TOTAL_CONNECTIONS |
+------------------+-----------+---------------------+-------------------+
| root             | localhost |                   1 |                 2 |
| NULL             | NULL      |                  20 |                23 |
| debian-sys-maint | localhost |                   0 |                35 |
+------------------+-----------+---------------------+-------------------+

1.1.1.2.9.2.1.3 Performance Schema cond_instances Table

Description

The cond_instances table lists all conditions while the server is executing. A condition, or instrumented condition object, is an internal code mechanism used for signalling that a specific event has occurred so that any threads waiting for this condition can continue.

The maximum number of conditions stored in the performance schema is determined by the performance_schema_max_cond_instances system variable.

ColumnDescription
NAMEClient user name for the connection, or NULL if an internal thread.
OBJECT_INSTANCE_BEGINAddress in memory of the instrumented condition.

1.1.1.2.9.2.1.4 Performance Schema events_stages_current Table

The events_stages_current table contains current stage events, with each row being a record of a thread and its most recent stage event.

The table contains the following columns:

ColumnDescription
THREAD_IDThread associated with the event. Together with EVENT_ID uniquely identifies the row.
EVENT_IDThread's current event number at the start of the event. Together with THREAD_ID uniquely identifies the row.
END_EVENT_IDNULL when the event starts, set to the thread's current event number at the end of the event.
EVENT_NAMEEvent instrument name and a NAME from the setup_instruments table
SOURCEName and line number of the source file containing the instrumented code that produced the event.
TIMER_STARTValue in picoseconds when the event timing started or NULL if timing is not collected.
TIMER_ENDValue in picoseconds when the event timing ended, or NULL if the event has not ended or timing is not collected.
TIMER_WAITValue in picoseconds of the event's duration or NULL if the event has not ended or timing is not collected.
NESTING_EVENT_IDEVENT_ID of event within which this event nests.
NESTING_EVENT_TYPENesting event type. One of transaction, statement, stage or wait.

It is possible to empty this table with a TRUNCATE TABLE statement.

The related tables, events_stages_history and events_stages_history_long derive their values from the current events.

1.1.1.2.9.2.1.5 Performance Schema events_stages_history Table

The events_stages_history table by default contains the ten most recent completed stage events per thread. This number can be adjusted by setting the performance_schema_events_stages_history_size system variable when the server starts up.

The table structure is identical to the events_stage_current table structure, and contains the following columns:

ColumnDescription
THREAD_IDThread associated with the event. Together with EVENT_ID uniquely identifies the row.
EVENT_IDThread's current event number at the start of the event. Together with THREAD_ID uniquely identifies the row.
END_EVENT_IDNULL when the event starts, set to the thread's current event number at the end of the event.
EVENT_NAMEEvent instrument name and a NAME from the setup_instruments table
SOURCEName and line number of the source file containing the instrumented code that produced the event.
TIMER_STARTValue in picoseconds when the event timing started or NULL if timing is not collected.
TIMER_ENDValue in picoseconds when the event timing ended, or NULL if timing is not collected.
TIMER_WAITValue in picoseconds of the event's duration or NULL if timing is not collected.
NESTING_EVENT_IDEVENT_ID of event within which this event nests.
NESTING_EVENT_TYPENesting event type. One of transaction, statement, stage or wait.

It is possible to empty this table with a TRUNCATE TABLE statement.

events_stages_current and events_stages_history_long are related tables.

1.1.1.2.9.2.1.6 Performance Schema events_stages_history_long Table

The events_stages_history_long table by default contains the ten thousand most recent completed stage events. This number can be adjusted by setting the performance_schema_events_stages_history_long_size system variable when the server starts up.

The table structure is identical to the events_stage_current table structure, and contains the following columns:

ColumnDescription
THREAD_IDThread associated with the event. Together with EVENT_ID uniquely identifies the row.
EVENT_IDThread's current event number at the start of the event. Together with THREAD_ID uniquely identifies the row.
END_EVENT_IDNULL when the event starts, set to the thread's current event number at the end of the event.
EVENT_NAMEEvent instrument name and a NAME from the setup_instruments table
SOURCEName and line number of the source file containing the instrumented code that produced the event.
TIMER_STARTValue in picoseconds when the event timing started or NULL if timing is not collected.
TIMER_ENDValue in picoseconds when the event timing ended, or NULL if timing is not collected.
TIMER_WAITValue in picoseconds of the event's duration or NULL if timing is not collected.
NESTING_EVENT_IDEVENT_ID of event within which this event nests.
NESTING_EVENT_TYPENesting event type. One of transaction, statement, stage or wait.

It is possible to empty this table with a TRUNCATE TABLE statement.

events_stages_current and events_stages_history are related tables.

1.1.1.2.9.2.1.7 Performance Schema events_stages_summary_by_account_by_event_name Table

The table lists stage events, summarized by account and event name.

It contains the following columns:

ColumnDescription
USERUser. Used together with HOST and EVENT_NAME for grouping events.
HOSTHost. Used together with USER and EVENT_NAME for grouping events.
EVENT_NAMEEvent name. Used together with USER and HOST for grouping events.
COUNT_STARNumber of summarized events, which includes all timed and untimed events.
SUM_TIMER_WAITTotal wait time of the timed summarized events.
MIN_TIMER_WAITMinimum wait time of the timed summarized events.
AVG_TIMER_WAITAverage wait time of the timed summarized events.
MAX_TIMER_WAITMaximum wait time of the timed summarized events.

Example

SELECT * FROM events_stages_summary_by_account_by_event_name\G
...
*************************** 325. row ***************************
          USER: NULL
          HOST: NULL
    EVENT_NAME: stage/sql/Waiting for event metadata lock
    COUNT_STAR: 0
SUM_TIMER_WAIT: 0
MIN_TIMER_WAIT: 0
AVG_TIMER_WAIT: 0
MAX_TIMER_WAIT: 0
*************************** 326. row ***************************
          USER: NULL
          HOST: NULL
    EVENT_NAME: stage/sql/Waiting for commit lock
    COUNT_STAR: 0
SUM_TIMER_WAIT: 0
MIN_TIMER_WAIT: 0
AVG_TIMER_WAIT: 0
MAX_TIMER_WAIT: 0
*************************** 327. row ***************************
          USER: NULL
          HOST: NULL
    EVENT_NAME: stage/aria/Waiting for a resource
    COUNT_STAR: 0
SUM_TIMER_WAIT: 0
MIN_TIMER_WAIT: 0
AVG_TIMER_WAIT: 0
MAX_TIMER_WAIT: 0

1.1.1.2.9.2.1.8 Performance Schema events_stages_summary_by_host_by_event_name Table

The table lists stage events, summarized by host and event name.

It contains the following columns:

ColumnDescription
HOSTHost. Used together with EVENT_NAME for grouping events.
EVENT_NAMEEvent name. Used together with HOST for grouping events.
COUNT_STARNumber of summarized events, which includes all timed and untimed events.
SUM_TIMER_WAITTotal wait time of the timed summarized events.
MIN_TIMER_WAITMinimum wait time of the timed summarized events.
AVG_TIMER_WAITAverage wait time of the timed summarized events.
MAX_TIMER_WAITMaximum wait time of the timed summarized events.

Example

SELECT * FROM events_stages_summary_by_host_by_event_name\G
...
*************************** 216. row ***************************
          HOST: NULL
    EVENT_NAME: stage/sql/Waiting for event metadata lock
    COUNT_STAR: 0
SUM_TIMER_WAIT: 0
MIN_TIMER_WAIT: 0
AVG_TIMER_WAIT: 0
MAX_TIMER_WAIT: 0
*************************** 217. row ***************************
          HOST: NULL
    EVENT_NAME: stage/sql/Waiting for commit lock
    COUNT_STAR: 0
SUM_TIMER_WAIT: 0
MIN_TIMER_WAIT: 0
AVG_TIMER_WAIT: 0
MAX_TIMER_WAIT: 0
*************************** 218. row ***************************
          HOST: NULL
    EVENT_NAME: stage/aria/Waiting for a resource
    COUNT_STAR: 0
SUM_TIMER_WAIT: 0
MIN_TIMER_WAIT: 0
AVG_TIMER_WAIT: 0
MAX_TIMER_WAIT: 0

1.1.1.2.9.2.1.9 Performance Schema events_stages_summary_by_thread_by_event_name Table

The table lists stage events, summarized by thread and event name.

It contains the following columns:

ColumnDescription
THREAD_IDThread associated with the event. Together with EVENT_NAME uniquely identifies the row.
EVENT_NAMEEvent name. Used together with THREAD_ID for grouping events.
COUNT_STARNumber of summarized events, which includes all timed and untimed events.
SUM_TIMER_WAITTotal wait time of the timed summarized events.
MIN_TIMER_WAITMinimum wait time of the timed summarized events.
AVG_TIMER_WAITAverage wait time of the timed summarized events.
MAX_TIMER_WAITMaximum wait time of the timed summarized events.

Example

SELECT * FROM events_stages_summary_by_thread_by_event_name\G
...
*************************** 2287. row ***************************
     THREAD_ID: 64
    EVENT_NAME: stage/sql/Waiting for event metadata lock
    COUNT_STAR: 0
SUM_TIMER_WAIT: 0
MIN_TIMER_WAIT: 0
AVG_TIMER_WAIT: 0
MAX_TIMER_WAIT: 0
*************************** 2288. row ***************************
     THREAD_ID: 64
    EVENT_NAME: stage/sql/Waiting for commit lock
    COUNT_STAR: 0
SUM_TIMER_WAIT: 0
MIN_TIMER_WAIT: 0
AVG_TIMER_WAIT: 0
MAX_TIMER_WAIT: 0
*************************** 2289. row ***************************
     THREAD_ID: 64
    EVENT_NAME: stage/aria/Waiting for a resource
    COUNT_STAR: 0
SUM_TIMER_WAIT: 0
MIN_TIMER_WAIT: 0
AVG_TIMER_WAIT: 0
MAX_TIMER_WAIT: 0

1.1.1.2.9.2.1.10 Performance Schema events_stages_summary_by_user_by_event_name Table

The table lists stage events, summarized by user and event name.

It contains the following columns:

ColumnDescription
USERUser. Used together with EVENT_NAME for grouping events.
EVENT_NAMEEvent name. Used together with USER for grouping events.
COUNT_STARNumber of summarized events, which includes all timed and untimed events.
SUM_TIMER_WAITTotal wait time of the timed summarized events.
MIN_TIMER_WAITMinimum wait time of the timed summarized events.
AVG_TIMER_WAITAverage wait time of the timed summarized events.
MAX_TIMER_WAITMaximum wait time of the timed summarized events.

Example

SELECT * FROM events_stages_summary_by_user_by_event_name\G
...
*************************** 325. row ***************************
          USER: NULL
    EVENT_NAME: stage/sql/Waiting for event metadata lock
    COUNT_STAR: 0
SUM_TIMER_WAIT: 0
MIN_TIMER_WAIT: 0
AVG_TIMER_WAIT: 0
MAX_TIMER_WAIT: 0
*************************** 326. row ***************************
          USER: NULL
    EVENT_NAME: stage/sql/Waiting for commit lock
    COUNT_STAR: 0
SUM_TIMER_WAIT: 0
MIN_TIMER_WAIT: 0
AVG_TIMER_WAIT: 0
MAX_TIMER_WAIT: 0
*************************** 327. row ***************************
          USER: NULL
    EVENT_NAME: stage/aria/Waiting for a resource
    COUNT_STAR: 0
SUM_TIMER_WAIT: 0
MIN_TIMER_WAIT: 0
AVG_TIMER_WAIT: 0
MAX_TIMER_WAIT: 0

1.1.1.2.9.2.1.11 Performance Schema events_stages_summary_global_by_event_name Table

The table lists stage events, summarized by thread and event name.

It contains the following columns:

ColumnDescription
EVENT_NAMEEvent name.
COUNT_STARNumber of summarized events, which includes all timed and untimed events.
SUM_TIMER_WAITTotal wait time of the timed summarized events.
MIN_TIMER_WAITMinimum wait time of the timed summarized events.
AVG_TIMER_WAITAverage wait time of the timed summarized events.
MAX_TIMER_WAITMaximum wait time of the timed summarized events.

Example

SELECT * FROM events_stages_summary_global_by_event_name\G
...
*************************** 106. row ***************************
    EVENT_NAME: stage/sql/Waiting for trigger metadata lock
    COUNT_STAR: 0
SUM_TIMER_WAIT: 0
MIN_TIMER_WAIT: 0
AVG_TIMER_WAIT: 0
MAX_TIMER_WAIT: 0
*************************** 107. row ***************************
    EVENT_NAME: stage/sql/Waiting for event metadata lock
    COUNT_STAR: 0
SUM_TIMER_WAIT: 0
MIN_TIMER_WAIT: 0
AVG_TIMER_WAIT: 0
MAX_TIMER_WAIT: 0
*************************** 108. row ***************************
    EVENT_NAME: stage/sql/Waiting for commit lock
    COUNT_STAR: 0
SUM_TIMER_WAIT: 0
MIN_TIMER_WAIT: 0
AVG_TIMER_WAIT: 0
MAX_TIMER_WAIT: 0
*************************** 109. row ***************************
    EVENT_NAME: stage/aria/Waiting for a resource
    COUNT_STAR: 0
SUM_TIMER_WAIT: 0
MIN_TIMER_WAIT: 0
AVG_TIMER_WAIT: 0
MAX_TIMER_WAIT: 0

1.1.1.2.9.2.1.12 Performance Schema events_statements_history Table

The events_statements_history table by default contains the ten most recent completed statement events per thread. This number can be adjusted by setting the performance_schema_events_statements_history_size system variable when the server starts up.

The table structure is identical to the events_statements_current table structure, and contains the following columns:

The table contains the following columns:

ColumnDescription
THREAD_IDThread associated with the event. Together with EVENT_ID uniquely identifies the row.
EVENT_IDThread's current event number at the start of the event. Together with THREAD_ID uniquely identifies the row.
END_EVENT_IDNULL when the event starts, set to the thread's current event number at the end of the event.
EVENT_NAMEEvent instrument name and a NAME from the setup_instruments table
SOURCEName and line number of the source file containing the instrumented code that produced the event.
TIMER_STARTValue in picoseconds when the event timing started or NULL if timing is not collected.
TIMER_ENDValue in picoseconds when the event timing ended, or NULL if timing is not collected.
TIMER_WAITValue in picoseconds of the event's duration or NULL if timing is not collected.
LOCK_TIMETime in picoseconds spent waiting for locks. The time is calculated in microseconds but stored in picoseconds for compatibility with other timings.
SQL_TEXTThe SQL statement, or NULL if the command is not associated with an SQL statement.
DIGESTStatement digest.
DIGEST_TEXTStatement digest text.
CURRENT_SCHEMAStatement's default database for the statement, or NULL if there was none.
OBJECT_SCHEMAReserved, currently NULL
OBJECT_NAMEReserved, currently NULL
OBJECT_TYPEReserved, currently NULL
OBJECT_INSTANCE_BEGINAddress in memory of the statement object.
MYSQL_ERRNOError code. See MariaDB Error Codes for a full list.
RETURNED_SQLSTATEThe SQLSTATE value.
MESSAGE_TEXTStatement error message. See MariaDB Error Codes.
ERRORS0 if SQLSTATE signifies completion (starting with 00) or warning (01), otherwise 1.
WARNINGSNumber of warnings from the diagnostics area.
ROWS_AFFECTEDNumber of rows affected the statement affected.
ROWS_SENTNumber of rows returned.
ROWS_EXAMINEDNumber of rows read during the statement's execution.
CREATED_TMP_DISK_TABLESNumber of on-disk temp tables created by the statement.
CREATED_TMP_TABLESNumber of temp tables created by the statement.
SELECT_FULL_JOINNumber of joins performed by the statement which did not use an index.
SELECT_FULL_RANGE_JOINNumber of joins performed by the statement which used a range search of the first table.
SELECT_RANGENumber of joins performed by the statement which used a range of the first table.
SELECT_RANGE_CHECKNumber of joins without keys performed by the statement that check for key usage after each row.
SELECT_SCANNumber of joins performed by the statement which used a full scan of the first table.
SORT_MERGE_PASSESNumber of merge passes by the sort algorithm performed by the statement. If too high, you may need to increase the sort_buffer_size.
SORT_RANGENumber of sorts performed by the statement which used a range.
SORT_ROWSNumber of rows sorted by the statement.
SORT_SCANNumber of sorts performed by the statement which used a full table scan.
NO_INDEX_USED0 if the statement performed a table scan with an index, 1 if without an index.
NO_GOOD_INDEX_USED0 if a good index was found for the statement, 1 if no good index was found. See the Range checked for each record description in the EXPLAIN article.
NESTING_EVENT_IDReserved, currently NULL.
NESTING_EVENT_TYPEReserved, currently NULL.

It is possible to empty this table with a TRUNCATE TABLE statement.

events_statements_current and events_statements_history_long are related tables.

1.1.1.2.9.2.1.13 Performance Schema events_statements_history_long Table

The events_statements_history_long table by default contains the ten thousand most recent completed statement events. This number can be adjusted by setting the performance_schema_events_statements_history_long_size system variable when the server starts up.

The table structure is identical to the events_statements_current table structure, and contains the following columns:

ColumnDescription
THREAD_IDThread associated with the event. Together with EVENT_ID uniquely identifies the row.
EVENT_IDThread's current event number at the start of the event. Together with THREAD_ID uniquely identifies the row.
END_EVENT_IDNULL when the event starts, set to the thread's current event number at the end of the event.
EVENT_NAMEEvent instrument name and a NAME from the setup_instruments table
SOURCEName and line number of the source file containing the instrumented code that produced the event.
TIMER_STARTValue in picoseconds when the event timing started or NULL if timing is not collected.
TIMER_ENDValue in picoseconds when the event timing ended, or NULL if timing is not collected.
TIMER_WAITValue in picoseconds of the event's duration or NULL if timing is not collected.
LOCK_TIMETime in picoseconds spent waiting for locks. The time is calculated in microseconds but stored in picoseconds for compatibility with other timings.
SQL_TEXTThe SQL statement, or NULL if the command is not associated with an SQL statement.
DIGESTStatement digest.
DIGEST_TEXTStatement digest text.
CURRENT_SCHEMAStatement's default database for the statement, or NULL if there was none.
OBJECT_SCHEMAReserved, currently NULL
OBJECT_NAMEReserved, currently NULL
OBJECT_TYPEReserved, currently NULL
OBJECT_INSTANCE_BEGINAddress in memory of the statement object.
MYSQL_ERRNOError code. See MariaDB Error Codes for a full list.
RETURNED_SQLSTATEThe SQLSTATE value.
MESSAGE_TEXTStatement error message. See MariaDB Error Codes.
ERRORS0 if SQLSTATE signifies completion (starting with 00) or warning (01), otherwise 1.
WARNINGSNumber of warnings from the diagnostics area.
ROWS_AFFECTEDNumber of rows affected the statement affected.
ROWS_SENTNumber of rows returned.
ROWS_EXAMINEDNumber of rows read during the statement's execution.
CREATED_TMP_DISK_TABLESNumber of on-disk temp tables created by the statement.
CREATED_TMP_TABLESNumber of temp tables created by the statement.
SELECT_FULL_JOINNumber of joins performed by the statement which did not use an index.
SELECT_FULL_RANGE_JOINNumber of joins performed by the statement which used a range search of the first table.
SELECT_RANGENumber of joins performed by the statement which used a range of the first table.
SELECT_RANGE_CHECKNumber of joins without keys performed by the statement that check for key usage after each row.
SELECT_SCANNumber of joins performed by the statement which used a full scan of the first table.
SORT_MERGE_PASSESNumber of merge passes by the sort algorithm performed by the statement. If too high, you may need to increase the sort_buffer_size.
SORT_RANGENumber of sorts performed by the statement which used a range.
SORT_ROWSNumber of rows sorted by the statement.
SORT_SCANNumber of sorts performed by the statement which used a full table scan.
NO_INDEX_USED0 if the statement performed a table scan with an index, 1 if without an index.
NO_GOOD_INDEX_USED0 if a good index was found for the statement, 1 if no good index was found. See the Range checked for each record description in the EXPLAIN article.
NESTING_EVENT_IDReserved, currently NULL.
NESTING_EVENT_TYPEReserved, currently NULL.

It is possible to empty this table with a TRUNCATE TABLE statement.

events_statements_current and events_statements_history are related tables.

1.1.1.2.9.2.1.14 Performance Schema events_statements_summary_by_account_by_event_name Table

The Performance Schema events_statements_summary_by_account_by_event_name table contains statement events summarized by account and event name. It contains the following columns:

ColumnDescription
USERUser. Used together with HOST and EVENT_NAME for grouping events.
HOSTHost. Used together with USER and EVENT_NAME for grouping events.
EVENT_NAMEEvent name. Used together with USER and HOST for grouping events.
COUNT_STARNumber of summarized events
SUM_TIMER_WAITTotal wait time of the summarized events that are timed.
MIN_TIMER_WAITMinimum wait time of the summarized events that are timed.
AVG_TIMER_WAITAverage wait time of the summarized events that are timed.
MAX_TIMER_WAITMaximum wait time of the summarized events that are timed.
SUM_LOCK_TIMESum of the LOCK_TIME column in the events_statements_current table.
SUM_ERRORSSum of the ERRORS column in the events_statements_current table.
SUM_WARNINGSSum of the WARNINGS column in the events_statements_current table.
SUM_ROWS_AFFECTEDSum of the ROWS_AFFECTED column in the events_statements_current table.
SUM_ROWS_SENTSum of the ROWS_SENT column in the events_statements_current table.
SUM_ROWS_EXAMINEDSum of the ROWS_EXAMINED column in the events_statements_current table.
SUM_CREATED_TMP_DISK_TABLESSum of the CREATED_TMP_DISK_TABLES column in the events_statements_current table.
SUM_CREATED_TMP_TABLESSum of the CREATED_TMP_TABLES column in the events_statements_current table.
SUM_SELECT_FULL_JOINSum of the SELECT_FULL_JOIN column in the events_statements_current table.
SUM_SELECT_FULL_RANGE_JOINSum of the SELECT_FULL_RANGE_JOIN column in the events_statements_current table.
SUM_SELECT_RANGESum of the SELECT_RANGE column in the events_statements_current table.
SUM_SELECT_RANGE_CHECKSum of the SELECT_RANGE_CHECK column in the events_statements_current table.
SUM_SELECT_SCANSum of the SELECT_SCAN column in the events_statements_current table.
SUM_SORT_MERGE_PASSESSum of the SORT_MERGE_PASSES column in the events_statements_current table.
SUM_SORT_RANGESum of the SORT_RANGE column in the events_statements_current table.
SUM_SORT_ROWSSum of the SORT_ROWS column in the events_statements_current table.
SUM_SORT_SCANSum of the SORT_SCAN column in the events_statements_current table.
SUM_NO_INDEX_USEDSum of the NO_INDEX_USED column in the events_statements_current table.
SUM_NO_GOOD_INDEX_USEDSum of the NO_GOOD_INDEX_USED column in the events_statements_current table.

The *_TIMER_WAIT columns only calculate results for timed events, as non-timed events have a NULL wait time.

Example

SELECT * FROM events_statements_summary_by_account_by_event_name\G
...
*************************** 521. row ***************************
                       USER: NULL
                       HOST: NULL
                 EVENT_NAME: statement/com/Error
                 COUNT_STAR: 0
             SUM_TIMER_WAIT: 0
             MIN_TIMER_WAIT: 0
             AVG_TIMER_WAIT: 0
             MAX_TIMER_WAIT: 0
              SUM_LOCK_TIME: 0
                 SUM_ERRORS: 0
               SUM_WARNINGS: 0
          SUM_ROWS_AFFECTED: 0
              SUM_ROWS_SENT: 0
          SUM_ROWS_EXAMINED: 0
SUM_CREATED_TMP_DISK_TABLES: 0
     SUM_CREATED_TMP_TABLES: 0
       SUM_SELECT_FULL_JOIN: 0
 SUM_SELECT_FULL_RANGE_JOIN: 0
           SUM_SELECT_RANGE: 0
     SUM_SELECT_RANGE_CHECK: 0
            SUM_SELECT_SCAN: 0
      SUM_SORT_MERGE_PASSES: 0
             SUM_SORT_RANGE: 0
              SUM_SORT_ROWS: 0
              SUM_SORT_SCAN: 0
          SUM_NO_INDEX_USED: 0
     SUM_NO_GOOD_INDEX_USED: 0
*************************** 522. row ***************************
                       USER: NULL
                       HOST: NULL
                 EVENT_NAME: statement/com/
                 COUNT_STAR: 0
             SUM_TIMER_WAIT: 0
             MIN_TIMER_WAIT: 0
             AVG_TIMER_WAIT: 0
             MAX_TIMER_WAIT: 0
              SUM_LOCK_TIME: 0
                 SUM_ERRORS: 0
               SUM_WARNINGS: 0
          SUM_ROWS_AFFECTED: 0
              SUM_ROWS_SENT: 0
          SUM_ROWS_EXAMINED: 0
SUM_CREATED_TMP_DISK_TABLES: 0
     SUM_CREATED_TMP_TABLES: 0
       SUM_SELECT_FULL_JOIN: 0
 SUM_SELECT_FULL_RANGE_JOIN: 0
           SUM_SELECT_RANGE: 0
     SUM_SELECT_RANGE_CHECK: 0
            SUM_SELECT_SCAN: 0
      SUM_SORT_MERGE_PASSES: 0
             SUM_SORT_RANGE: 0
              SUM_SORT_ROWS: 0
              SUM_SORT_SCAN: 0
          SUM_NO_INDEX_USED: 0
     SUM_NO_GOOD_INDEX_USED: 0

1.1.1.2.9.2.1.15 Performance Schema events_statements_summary_by_digest Table

The Performance Schema digest is a hashed, normalized form of a statement with the specific data values removed. It allows statistics to be gathered for similar kinds of statements.

The Performance Schema events_statements_summary_by_digest table records statement events summarized by schema and digest. It contains the following columns:

ColumnDescription
SCHEMA NAMEDatabase name. Records are summarised together with DIGEST.
DIGESTPerformance Schema digest. Records are summarised together with SCHEMA NAME.
DIGEST TEXTThe unhashed form of the digest.
COUNT_STARNumber of summarized events
SUM_TIMER_WAITTotal wait time of the summarized events that are timed.
MIN_TIMER_WAITMinimum wait time of the summarized events that are timed.
AVG_TIMER_WAITAverage wait time of the summarized events that are timed.
MAX_TIMER_WAITMaximum wait time of the summarized events that are timed.
SUM_LOCK_TIMESum of the LOCK_TIME column in the events_statements_current table.
SUM_ERRORSSum of the ERRORS column in the events_statements_current table.
SUM_WARNINGSSum of the WARNINGS column in the events_statements_current table.
SUM_ROWS_AFFECTEDSum of the ROWS_AFFECTED column in the events_statements_current table.
SUM_ROWS_SENTSum of the ROWS_SENT column in the events_statements_current table.
SUM_ROWS_EXAMINEDSum of the ROWS_EXAMINED column in the events_statements_current table.
SUM_CREATED_TMP_DISK_TABLESSum of the CREATED_TMP_DISK_TABLES column in the events_statements_current table.
SUM_CREATED_TMP_TABLESSum of the CREATED_TMP_TABLES column in the events_statements_current table.
SUM_SELECT_FULL_JOINSum of the SELECT_FULL_JOIN column in the events_statements_current table.
SUM_SELECT_FULL_RANGE_JOINSum of the SELECT_FULL_RANGE_JOIN column in the events_statements_current table.
SUM_SELECT_RANGESum of the SELECT_RANGE column in the events_statements_current table.
SUM_SELECT_RANGE_CHECKSum of the SELECT_RANGE_CHECK column in the events_statements_current table.
SUM_SELECT_SCANSum of the SELECT_SCAN column in the events_statements_current table.
SUM_SORT_MERGE_PASSESSum of the SORT_MERGE_PASSES column in the events_statements_current table.
SUM_SORT_RANGESum of the SORT_RANGE column in the events_statements_current table.
SUM_SORT_ROWSSum of the SORT_ROWS column in the events_statements_current table.
SUM_SORT_SCANSum of the SORT_SCAN column in the events_statements_current table.
SUM_NO_INDEX_USEDSum of the NO_INDEX_USED column in the events_statements_current table.
SUM_NO_GOOD_INDEX_USEDSum of the NO_GOOD_INDEX_USED column in the events_statements_current table.
FIRST_SEENTime at which the digest was first seen.
LAST_SEENTime at which the digest was most recently seen.

The *_TIMER_WAIT columns only calculate results for timed events, as non-timed events have a NULL wait time.

The events_statements_summary_by_digest table is limited in size by the performance_schema_digests_size system variable. Once the limit has been reached and the table is full, all entries are aggregated in a row with a NULL digest. The COUNT_STAR value of this NULL row indicates how many digests are recorded in the row and therefore gives an indication of whether performance_schema_digests_size should be increased to provide more accurate statistics.

1.1.1.2.9.2.1.16 Performance Schema events_statements_summary_by_host_by_event_name Table

The Performance Schema events_statements_summary_by_host_by_event_name table contains statement events summarized by host and event name. It contains the following columns:

ColumnDescription
HOSTHost. Used together with EVENT_NAME for grouping events.
EVENT_NAMEEvent name. Used together with HOST for grouping events.
COUNT_STARNumber of summarized events
SUM_TIMER_WAITTotal wait time of the summarized events that are timed.
MIN_TIMER_WAITMinimum wait time of the summarized events that are timed.
AVG_TIMER_WAITAverage wait time of the summarized events that are timed.
MAX_TIMER_WAITMaximum wait time of the summarized events that are timed.
SUM_LOCK_TIMESum of the LOCK_TIME column in the events_statements_currentd table.
SUM_ERRORSSum of the ERRORS column in the events_statements_current table.
SUM_WARNINGSSum of the WARNINGS column in the events_statements_current table.
SUM_ROWS_AFFECTEDSum of the ROWS_AFFECTED column in the events_statements_current table.
SUM_ROWS_SENTSum of the ROWS_SENT column in the events_statements_current table.
SUM_ROWS_EXAMINEDSum of the ROWS_EXAMINED column in the events_statements_current table.
SUM_CREATED_TMP_DISK_TABLESSum of the CREATED_TMP_DISK_TABLES column in the events_statements_current table.
SUM_CREATED_TMP_TABLESSum of the CREATED_TMP_TABLES column in the events_statements_current table.
SUM_SELECT_FULL_JOINSum of the SELECT_FULL_JOIN column in the events_statements_current table.
SUM_SELECT_FULL_RANGE_JOINSum of the SELECT_FULL_RANGE_JOINW column in the events_statements_current table.
SUM_SELECT_RANGESum of the SELECT_RANGE column in the events_statements_current table.
SUM_SELECT_RANGE_CHECKSum of the SELECT_RANGE_CHECK column in the events_statements_current table.
SUM_SELECT_SCANSum of the SELECT_SCAN column in the events_statements_current table.
SUM_SORT_MERGE_PASSESSum of the SORT_MERGE_PASSES column in the events_statements_current table.
SUM_SORT_RANGESum of the SORT_RANGE column in the events_statements_current table.
SUM_SORT_ROWSSum of the SORT_ROWS column in the events_statements_current table.
SUM_SORT_SCANSum of the SORT_SCAN column in the events_statements_current table.
SUM_NO_INDEX_USEDSum of the NO_INDEX_USED column in the events_statements_current table.
SUM_NO_GOOD_INDEX_USEDSum of the NO_GOOD_INDEX_USED column in the events_statements_current table.

The *_TIMER_WAIT columns only calculate results for timed events, as non-timed events have a NULL wait time.

Example

SELECT * FROM events_statements_summary_by_host_by_event_name\G
...
*************************** 347. row ***************************
                       HOST: NULL
                 EVENT_NAME: statement/com/Error
                 COUNT_STAR: 0
             SUM_TIMER_WAIT: 0
             MIN_TIMER_WAIT: 0
             AVG_TIMER_WAIT: 0
             MAX_TIMER_WAIT: 0
              SUM_LOCK_TIME: 0
                 SUM_ERRORS: 0
               SUM_WARNINGS: 0
          SUM_ROWS_AFFECTED: 0
              SUM_ROWS_SENT: 0
          SUM_ROWS_EXAMINED: 0
SUM_CREATED_TMP_DISK_TABLES: 0
     SUM_CREATED_TMP_TABLES: 0
       SUM_SELECT_FULL_JOIN: 0
 SUM_SELECT_FULL_RANGE_JOIN: 0
           SUM_SELECT_RANGE: 0
     SUM_SELECT_RANGE_CHECK: 0
            SUM_SELECT_SCAN: 0
      SUM_SORT_MERGE_PASSES: 0
             SUM_SORT_RANGE: 0
              SUM_SORT_ROWS: 0
              SUM_SORT_SCAN: 0
          SUM_NO_INDEX_USED: 0
     SUM_NO_GOOD_INDEX_USED: 0
*************************** 348. row ***************************
                       HOST: NULL
                 EVENT_NAME: statement/com/
                 COUNT_STAR: 0
             SUM_TIMER_WAIT: 0
             MIN_TIMER_WAIT: 0
             AVG_TIMER_WAIT: 0
             MAX_TIMER_WAIT: 0
              SUM_LOCK_TIME: 0
                 SUM_ERRORS: 0
               SUM_WARNINGS: 0
          SUM_ROWS_AFFECTED: 0
              SUM_ROWS_SENT: 0
          SUM_ROWS_EXAMINED: 0
SUM_CREATED_TMP_DISK_TABLES: 0
     SUM_CREATED_TMP_TABLES: 0
       SUM_SELECT_FULL_JOIN: 0
 SUM_SELECT_FULL_RANGE_JOIN: 0
           SUM_SELECT_RANGE: 0
     SUM_SELECT_RANGE_CHECK: 0
            SUM_SELECT_SCAN: 0
      SUM_SORT_MERGE_PASSES: 0
             SUM_SORT_RANGE: 0
              SUM_SORT_ROWS: 0
              SUM_SORT_SCAN: 0
          SUM_NO_INDEX_USED: 0
     SUM_NO_GOOD_INDEX_USED: 0

1.1.1.2.9.2.1.17 Performance Schema events_statements_summary_by_program Table

MariaDB starting with 10.5.2

The events_statements_summary_by_program table, along with many other new Performance Schema tables, was added in MariaDB 10.5.2.

Each row in the the Performance Schema events_statements_summary_by_program table summarizes events for a particular stored program (stored procedure, stored function, trigger or event).

It contains the following fields.

ColumnTypeNullDescription
OBJECT_TYPEenum('EVENT', 'FUNCTION', 'PROCEDURE', 'TABLE', 'TRIGGER')YESObject type for which the summary is generated.
OBJECT_SCHEMAvarchar(64)NOThe schema of the object for which the summary is generated.
OBJECT_NAMEvarchar(64)NOThe name of the object for which the summary is generated.
COUNT_STARbigint(20) unsignedNOThe number of summarized events (from events_statements_current). This value includes all events, whether timed or nontimed.
SUM_TIMER_WAITbigint(20) unsignedNOThe number of summarized events (from events_statements_current). This value includes all events, whether timed or nontimed.
MIN_TIMER_WAITbigint(20) unsignedNOThe minimum wait time of the summarized timed events.
AVG_TIMER_WAITbigint(20) unsignedNOThe average wait time of the summarized timed events.
MAX_TIMER_WAITbigint(20) unsignedNOThe maximum wait time of the summarized timed events.
COUNT_STATEMENTSbigint(20) unsignedNOTotal number of nested statements invoked during stored program execution.
SUM_STATEMENTS_WAITbigint(20) unsignedNOThe total wait time of the summarized timed statements. This value is calculated only for timed statements because nontimed statements have a wait time of NULL. The same is true for the other xxx_STATEMENT_WAIT values.
MIN_STATEMENTS_WAITbigint(20) unsignedNOThe minimum wait time of the summarized timed statements.
AVG_STATEMENTS_WAITbigint(20) unsignedNOThe average wait time of the summarized timed statements.
MAX_STATEMENTS_WAITbigint(20) unsignedNOThe maximum wait time of the summarized timed statements.
SUM_LOCK_TIMEbigint(20) unsignedNOThe total time spent (in picoseconds) waiting for table locks for the summarized statements.
SUM_ERRORSbigint(20) unsignedNOThe total number of errors that occurend for the summarized statements.
SUM_WARNINGSbigint(20) unsignedNOThe total number of warnings that occurend for the summarized statements.
SUM_ROWS_AFFECTEDbigint(20) unsignedNOThe total number of affected rows by the summarized statements.
SUM_ROWS_SENTbigint(20) unsignedNOThe total number of rows returned by the summarized statements.
SUM_ROWS_EXAMINEDbigint(20) unsignedNOThe total number of rows examined by the summarized statements.The total number of affected rows by the summarized statements.
SUM_CREATED_TMP_DISK_TABLESbigint(20) unsignedNOThe total number of on-disk temporary tables created by the summarized statements.
SUM_CREATED_TMP_TABLESbigint(20) unsignedNOThe total number of in-memory temporary tables created by the summarized statements.
SUM_SELECT_FULL_JOINbigint(20) unsignedNOThe total number of full joins executed by the summarized statements.
SUM_SELECT_FULL_RANGE_JOINbigint(20) unsignedNOThe total number of range search joins executed by the summarized statements.
SUM_SELECT_RANGEbigint(20) unsignedNOThe total number of joins that used ranges on the first table executed by the summarized statements.
SUM_SELECT_RANGE_CHECKbigint(20) unsignedNOThe total number of joins that check for key usage after each row executed by the summarized statements.
SUM_SELECT_SCANbigint(20) unsignedNOThe total number of joins that did a full scan of the first table executed by the summarized statements.
SUM_SORT_MERGE_PASSESbigint(20) unsignedNOThe total number of merge passes that the sort algorithm has had to do for the summarized statements.
SUM_SORT_RANGEbigint(20) unsignedNOThe total number of sorts that were done using ranges for the summarized statements.
SUM_SORT_ROWSbigint(20) unsignedNOThe total number of sorted rows that were sorted by the summarized statements.
SUM_SORT_SCANbigint(20) unsignedNOThe total number of sorts that were done by scanning the table by the summarized statements.
SUM_NO_INDEX_USEDbigint(20) unsignedNOThe total number of statements that performed a table scan without using an index.
SUM_NO_GOOD_INDEX_USEDbigint(20) unsignedNOThe total number of statements where no good index was found.

1.1.1.2.9.2.1.18 Performance Schema events_statements_summary_by_thread_by_event_name Table

The Performance Schema events_statements_summary_by_thread_by_event_name table contains statement events summarized by thread and event name. It contains the following columns:

ColumnDescription
THREAD_IDThread associated with the event. Together with EVENT_NAME uniquely identifies the row.
EVENT_NAMEEvent name. Used together with THREAD_ID for grouping events.
COUNT_STARNumber of summarized events
SUM_TIMER_WAITTotal wait time of the summarized events that are timed.
MIN_TIMER_WAITMinimum wait time of the summarized events that are timed.
AVG_TIMER_WAITAverage wait time of the summarized events that are timed.
MAX_TIMER_WAITMaximum wait time of the summarized events that are timed.
SUM_LOCK_TIMESum of the LOCK_TIME column in the events_statements_current table.
SUM_ERRORSSum of the ERRORS column in the events_statements_current table.
SUM_WARNINGSSum of the WARNINGS column in the events_statements_current table.
SUM_ROWS_AFFECTEDSum of the ROWS_AFFECTED column in the events_statements_current table.
SUM_ROWS_SENTSum of the ROWS_SENT column in the events_statements_current table.
SUM_ROWS_EXAMINEDSum of the ROWS_EXAMINED column in the events_statements_current table.
SUM_CREATED_TMP_DISK_TABLESSum of the CREATED_TMP_DISK_TABLES column in the events_statements_current table.
SUM_CREATED_TMP_TABLESSum of the CREATED_TMP_TABLES column in the events_statements_current table.
SUM_SELECT_FULL_JOINSum of the SELECT_FULL_JOIN column in the events_statements_current table.
SUM_SELECT_FULL_RANGE_JOINSum of the SELECT_FULL_RANGE_JOIN column in the events_statements_current table.
SUM_SELECT_RANGESum of the SELECT_RANGE column in the events_statements_current table.
SUM_SELECT_RANGE_CHECKSum of the SELECT_RANGE_CHECK column in the events_statements_current table.
SUM_SELECT_SCANSum of the SELECT_SCAN column in the events_statements_current table.
SUM_SORT_MERGE_PASSESSum of the SORT_MERGE_PASSES column in the events_statements_current table.
SUM_SORT_RANGESum of the SORT_RANGE column in the events_statements_current table.
SUM_SORT_ROWSSum of the SORT_ROWS column in the events_statements_current table.
SUM_SORT_SCANSum of the SORT_SCAN column in the events_statements_current table.
SUM_NO_INDEX_USEDSum of the NO_INDEX_USED column in the events_statements_current table.
SUM_NO_GOOD_INDEX_USEDSum of the NO_GOOD_INDEX_USED column in the events_statements_current table.

The *_TIMER_WAIT columns only calculate results for timed events, as non-timed events have a NULL wait time.

Example

SELECT * FROM events_statements_summary_by_thread_by_event_name\G
...
*************************** 3653. row ***************************
                  THREAD_ID: 64
                 EVENT_NAME: statement/com/Error
                 COUNT_STAR: 0
             SUM_TIMER_WAIT: 0
             MIN_TIMER_WAIT: 0
             AVG_TIMER_WAIT: 0
             MAX_TIMER_WAIT: 0
              SUM_LOCK_TIME: 0
                 SUM_ERRORS: 0
               SUM_WARNINGS: 0
          SUM_ROWS_AFFECTED: 0
              SUM_ROWS_SENT: 0
          SUM_ROWS_EXAMINED: 0
SUM_CREATED_TMP_DISK_TABLES: 0
     SUM_CREATED_TMP_TABLES: 0
       SUM_SELECT_FULL_JOIN: 0
 SUM_SELECT_FULL_RANGE_JOIN: 0
           SUM_SELECT_RANGE: 0
     SUM_SELECT_RANGE_CHECK: 0
            SUM_SELECT_SCAN: 0
      SUM_SORT_MERGE_PASSES: 0
             SUM_SORT_RANGE: 0
              SUM_SORT_ROWS: 0
              SUM_SORT_SCAN: 0
          SUM_NO_INDEX_USED: 0
     SUM_NO_GOOD_INDEX_USED: 0
*************************** 3654. row ***************************
                  THREAD_ID: 64
                 EVENT_NAME: statement/com/
                 COUNT_STAR: 0
             SUM_TIMER_WAIT: 0
             MIN_TIMER_WAIT: 0
             AVG_TIMER_WAIT: 0
             MAX_TIMER_WAIT: 0
              SUM_LOCK_TIME: 0
                 SUM_ERRORS: 0
               SUM_WARNINGS: 0
          SUM_ROWS_AFFECTED: 0
              SUM_ROWS_SENT: 0
          SUM_ROWS_EXAMINED: 0
SUM_CREATED_TMP_DISK_TABLES: 0
     SUM_CREATED_TMP_TABLES: 0
       SUM_SELECT_FULL_JOIN: 0
 SUM_SELECT_FULL_RANGE_JOIN: 0
           SUM_SELECT_RANGE: 0
     SUM_SELECT_RANGE_CHECK: 0
            SUM_SELECT_SCAN: 0
      SUM_SORT_MERGE_PASSES: 0
             SUM_SORT_RANGE: 0
              SUM_SORT_ROWS: 0
              SUM_SORT_SCAN: 0
          SUM_NO_INDEX_USED: 0
     SUM_NO_GOOD_INDEX_USED: 0

1.1.1.2.9.2.1.19 Performance Schema events_statements_summary_by_user_by_event_name Table

The Performance Schema events_statements_summary_by_user_by_event_name table contains statement events summarized by user and event name. It contains the following columns:

ColumnDescription
USERUser. Used together with EVENT_NAME for grouping events.
EVENT_NAMEEvent name. Used together with USER for grouping events.
COUNT_STARNumber of summarized events
SUM_TIMER_WAITTotal wait time of the summarized events that are timed.
MIN_TIMER_WAITMinimum wait time of the summarized events that are timed.
AVG_TIMER_WAITAverage wait time of the summarized events that are timed.
MAX_TIMER_WAITMaximum wait time of the summarized events that are timed.
SUM_LOCK_TIMESum of the LOCK_TIME column in the events_statements_current table.
SUM_ERRORSSum of the ERRORS column in the events_statements_current table.
SUM_WARNINGSSum of the WARNINGS column in the events_statements_current table.
SUM_ROWS_AFFECTEDSum of the ROWS_AFFECTED column in the events_statements_current table.
SUM_ROWS_SENTSum of the ROWS_SENT column in the events_statements_current table.
SUM_ROWS_EXAMINEDSum of the ROWS_EXAMINED column in the events_statements_current table.
SUM_CREATED_TMP_DISK_TABLESSum of the CREATED_TMP_DISK_TABLES column in the events_statements_current table.
SUM_CREATED_TMP_TABLESSum of the CREATED_TMP_TABLES column in the events_statements_current table.
SUM_SELECT_FULL_JOINSum of the SELECT_FULL_JOIN column in the events_statements_current table.
SUM_SELECT_FULL_RANGE_JOINSum of the SELECT_FULL_RANGE_JOIN column in the events_statements_current table.
SUM_SELECT_RANGESum of the SELECT_RANGE column in the events_statements_current table.
SUM_SELECT_RANGE_CHECKSum of the SELECT_RANGE_CHECK column in the events_statements_current table.
SUM_SELECT_SCANSum of the SELECT_SCAN column in the events_statements_current table.
SUM_SORT_MERGE_PASSESSum of the SORT_MERGE_PASSES column in the events_statements_current table.
SUM_SORT_RANGESum of the SORT_RANGE column in the events_statements_current table.
SUM_SORT_ROWSSum of the SORT_ROWS column in the events_statements_current table.
SUM_SORT_SCANSum of the SORT_SCAN column in the events_statements_current table.
SUM_NO_INDEX_USEDSum of the NO_INDEX_USED column in the events_statements_current table.
SUM_NO_GOOD_INDEX_USEDSum of the NO_GOOD_INDEX_USED column in the events_statements_current table.

The *_TIMER_WAIT columns only calculate results for timed events, as non-timed events have a NULL wait time.

Example

SELECT * FROM events_statements_summary_by_user_by_event_name\G
...
*************************** 521. row ***************************
                       USER: NULL
                 EVENT_NAME: statement/com/Error
                 COUNT_STAR: 0
             SUM_TIMER_WAIT: 0
             MIN_TIMER_WAIT: 0
             AVG_TIMER_WAIT: 0
             MAX_TIMER_WAIT: 0
              SUM_LOCK_TIME: 0
                 SUM_ERRORS: 0
               SUM_WARNINGS: 0
          SUM_ROWS_AFFECTED: 0
              SUM_ROWS_SENT: 0
          SUM_ROWS_EXAMINED: 0
SUM_CREATED_TMP_DISK_TABLES: 0
     SUM_CREATED_TMP_TABLES: 0
       SUM_SELECT_FULL_JOIN: 0
 SUM_SELECT_FULL_RANGE_JOIN: 0
           SUM_SELECT_RANGE: 0
     SUM_SELECT_RANGE_CHECK: 0
            SUM_SELECT_SCAN: 0
      SUM_SORT_MERGE_PASSES: 0
             SUM_SORT_RANGE: 0
              SUM_SORT_ROWS: 0
              SUM_SORT_SCAN: 0
          SUM_NO_INDEX_USED: 0
     SUM_NO_GOOD_INDEX_USED: 0
*************************** 522. row ***************************
                       USER: NULL
                 EVENT_NAME: statement/com/
                 COUNT_STAR: 0
             SUM_TIMER_WAIT: 0
             MIN_TIMER_WAIT: 0
             AVG_TIMER_WAIT: 0
             MAX_TIMER_WAIT: 0
              SUM_LOCK_TIME: 0
                 SUM_ERRORS: 0
               SUM_WARNINGS: 0
          SUM_ROWS_AFFECTED: 0
              SUM_ROWS_SENT: 0
          SUM_ROWS_EXAMINED: 0
SUM_CREATED_TMP_DISK_TABLES: 0
     SUM_CREATED_TMP_TABLES: 0
       SUM_SELECT_FULL_JOIN: 0
 SUM_SELECT_FULL_RANGE_JOIN: 0
           SUM_SELECT_RANGE: 0
     SUM_SELECT_RANGE_CHECK: 0
            SUM_SELECT_SCAN: 0
      SUM_SORT_MERGE_PASSES: 0
             SUM_SORT_RANGE: 0
              SUM_SORT_ROWS: 0
              SUM_SORT_SCAN: 0
          SUM_NO_INDEX_USED: 0
     SUM_NO_GOOD_INDEX_USED: 0

1.1.1.2.9.2.1.20 Performance Schema events_statements_summary_global_by_event_name Table

The Performance Schema events_statements_summary_global_by_event_name table contains statement events summarized by event name. It contains the following columns:

ColumnDescription
EVENT_NAMEEvent name.
COUNT_STARNumber of summarized events
SUM_TIMER_WAITTotal wait time of the summarized events that are timed.
MIN_TIMER_WAITMinimum wait time of the summarized events that are timed.
AVG_TIMER_WAITAverage wait time of the summarized events that are timed.
MAX_TIMER_WAITMaximum wait time of the summarized events that are timed.
SUM_LOCK_TIMESum of the LOCK_TIME column in the events_statements_current table.
SUM_ERRORSSum of the ERRORS column in the events_statements_current table.
SUM_WARNINGSSum of the WARNINGS column in the events_statements_current table.
SUM_ROWS_AFFECTEDSum of the ROWS_AFFECTED column in the events_statements_current table.
SUM_ROWS_SENTSum of the ROWS_SENT column in the events_statements_current table.
SUM_ROWS_EXAMINEDSum of the ROWS_EXAMINED column in the events_statements_current table.
SUM_CREATED_TMP_DISK_TABLESSum of the CREATED_TMP_DISK_TABLES column in the events_statements_current table.
SUM_CREATED_TMP_TABLESSum of the CREATED_TMP_TABLES column in the events_statements_current table.
SUM_SELECT_FULL_JOINSum of the SELECT_FULL_JOIN column in the events_statements_current table.
SUM_SELECT_FULL_RANGE_JOINSum of the SELECT_FULL_RANGE_JOIN column in the events_statements_current table.
SUM_SELECT_RANGESum of the SELECT_RANGE column in the events_statements_current table.
SUM_SELECT_RANGE_CHECKSum of the SELECT_RANGE_CHECK column in the events_statements_current table.
SUM_SELECT_SCANSum of the SELECT_SCAN column in the events_statements_current table.
SUM_SORT_MERGE_PASSESSum of the SORT_MERGE_PASSES column in the events_statements_current table.
SUM_SORT_RANGESum of the SORT_RANGE column in the events_statements_current table.
SUM_SORT_ROWSSum of the SORT_ROWS column in the events_statements_current table.
SUM_SORT_SCANSum of the SORT_SCAN column in the events_statements_current table.
SUM_NO_INDEX_USEDSum of the NO_INDEX_USED column in the events_statements_current table.
SUM_NO_GOOD_INDEX_USEDSum of the NO_GOOD_INDEX_USED column in the events_statements_current table.

The *_TIMER_WAIT columns only calculate results for timed events, as non-timed events have a NULL wait time.

Example

SELECT * FROM events_statements_summary_global_by_event_name\G
...
*************************** 173. row ***************************
                 EVENT_NAME: statement/com/Error
                 COUNT_STAR: 0
             SUM_TIMER_WAIT: 0
             MIN_TIMER_WAIT: 0
             AVG_TIMER_WAIT: 0
             MAX_TIMER_WAIT: 0
              SUM_LOCK_TIME: 0
                 SUM_ERRORS: 0
               SUM_WARNINGS: 0
          SUM_ROWS_AFFECTED: 0
              SUM_ROWS_SENT: 0
          SUM_ROWS_EXAMINED: 0
SUM_CREATED_TMP_DISK_TABLES: 0
     SUM_CREATED_TMP_TABLES: 0
       SUM_SELECT_FULL_JOIN: 0
 SUM_SELECT_FULL_RANGE_JOIN: 0
           SUM_SELECT_RANGE: 0
     SUM_SELECT_RANGE_CHECK: 0
            SUM_SELECT_SCAN: 0
      SUM_SORT_MERGE_PASSES: 0
             SUM_SORT_RANGE: 0
              SUM_SORT_ROWS: 0
              SUM_SORT_SCAN: 0
          SUM_NO_INDEX_USED: 0
     SUM_NO_GOOD_INDEX_USED: 0
*************************** 174. row ***************************
                 EVENT_NAME: statement/com/
                 COUNT_STAR: 0
             SUM_TIMER_WAIT: 0
             MIN_TIMER_WAIT: 0
             AVG_TIMER_WAIT: 0
             MAX_TIMER_WAIT: 0
              SUM_LOCK_TIME: 0
                 SUM_ERRORS: 0
               SUM_WARNINGS: 0
          SUM_ROWS_AFFECTED: 0
              SUM_ROWS_SENT: 0
          SUM_ROWS_EXAMINED: 0
SUM_CREATED_TMP_DISK_TABLES: 0
     SUM_CREATED_TMP_TABLES: 0
       SUM_SELECT_FULL_JOIN: 0
 SUM_SELECT_FULL_RANGE_JOIN: 0
           SUM_SELECT_RANGE: 0
     SUM_SELECT_RANGE_CHECK: 0
            SUM_SELECT_SCAN: 0
      SUM_SORT_MERGE_PASSES: 0
             SUM_SORT_RANGE: 0
              SUM_SORT_ROWS: 0
              SUM_SORT_SCAN: 0
          SUM_NO_INDEX_USED: 0
     SUM_NO_GOOD_INDEX_USED: 0

1.1.1.2.9.2.1.21 Performance Schema events_transactions_current Table

MariaDB starting with 10.5.2

The events_transactions_current table was introduced in MariaDB 10.5.2.

The events_transactions_current table contains current transaction events for each thread.

The table size cannot be figured, and always stores one row for each thread, showing the current status of the thread's most recent monitored transaction event.

The table contains the following columns:

ColumnTypeDescription
THREAD_IDbigint(20) unsignedThe thread associated with the event.
EVENT_IDbigint(20) unsignedThe event id associated with the event.
END_EVENT_IDbigint(20) unsignedThis column is set to NULL when the event starts and updated to the thread current event number when the event ends.
EVENT_NAMEvarchar(128)The name of the instrument from which the event was collected. This is a NAME value from the setup_instruments table.
STATEenum('ACTIVE', 'COMMITTED', 'ROLLED BACK')The current transaction state. The value is ACTIVE (after START TRANSACTION or BEGIN), COMMITTED (after COMMIT), or ROLLED BACK (after ROLLBACK).
TRX_IDbigint(20) unsignedUnused.
GTIDvarchar(64)Transaction GTID, using the format DOMAIN-SERVER_ID-SEQUENCE_NO.
XID_FORMAT_IDint(11)XA transaction format ID for GTRID and BQUAL values.
XID_GTRIDvarchar(130)XA global transaction ID.
XID_BQUALvarchar(130)XA transaction branch qualifier.
XA_STATEvarchar(64)The state of the XA transaction. The value is ACTIVE (after XA START), IDLE (after XA END), PREPARED (after XA PREPARE), ROLLED BACK (after XA ROLLBACK), or COMMITTED (after XA COMMIT).
SOURCEvarchar(64)The name of the source file containing the instrumented code that produced the event and the line number in the file at which the instrumentation occurs.
TIMER_STARTbigint(20) unsignedThe unit is picoseconds. When event timing started. NULL if event has no timing information.
TIMER_ENDbigint(20) unsignedThe unit is picoseconds. When event timing ended. NULL if event has no timing information.
TIMER_WAITbigint(20) unsignedThe unit is picoseconds. Event duration. NULL if event has not timing information.
ACCESS_MODEenum('READ ONLY', 'READ WRITE')Transaction access mode.
ISOLATION_LEVELvarchar(64)Transaction isolation level. One of: REPEATABLE READ, READ COMMITTED, READ UNCOMMITTED, or SERIALIZABLE.
AUTOCOMMITenum('YES','NO')Whether autcommit mode was enabled when the transaction started.
NUMBER_OF_SAVEPOINTSbigint(20) unsignedThe number of SAVEPOINT statements issued during the transaction.
NUMBER_OF_ROLLBACK_TO_SAVEPOINTbigint(20) unsignedThe number of ROLLBACK_TO_SAVEPOINT statements issued during the transaction.
NUMBER_OF_RELEASE_SAVEPOINTbigint(20) unsignedThe number of RELEASE_SAVEPOINT statements issued during the transaction.
OBJECT_INSTANCE_BEGINbigint(20) unsignedUnused.
NESTING_EVENT_IDbigint(20) unsignedThe EVENT_ID value of the event within which this event is nested.
NESTING_EVENT_TYPEenum('TRANSACTION', 'STATEMENT', 'STAGE', 'WAIT')The nesting event type.

1.1.1.2.9.2.1.22 Performance Schema events_transactions_history Table

MariaDB starting with 10.5.2

The events_transactions_history table was introduced in MariaDB 10.5.2.

The events_transactions_history table contains the most recent completed transaction events for each thread.

The number of records stored per thread in the table is determined by the performance_schema_events_transactions_history_size system variable, which is autosized on startup.

If adding a completed transaction event would cause the table to exceed this limit, the oldest thread row is discarded.

All of a thread's rows are discarded when the thread ends.

The table contains the following columns:

ColumnTypeDescription
THREAD_IDbigint(20) unsignedThe thread associated with the event.
EVENT_IDbigint(20) unsignedThe event id associated with the event.
END_EVENT_IDbigint(20) unsignedThis column is set to NULL when the event starts and updated to the thread current event number when the event ends.
EVENT_NAMEvarchar(128)The name of the instrument from which the event was collected. This is a NAME value from the setup_instruments table.
STATEenum('ACTIVE', 'COMMITTED',' ROLLED BACK')The current transaction state. The value is ACTIVE (after START TRANSACTION or BEGIN), COMMITTED (after COMMIT), or ROLLED BACK (after ROLLBACK).
TRX_IDbigint(20) unsignedUnused.
GTIDvarchar(64)Transaction GTID, using the format DOMAIN-SERVER_ID-SEQUENCE_NO.
XID_FORMAT_IDint(11)XA transaction format ID for GTRID and BQUAL values.
XID_GTRIDvarchar(130)XA global transaction ID.
XID_BQUALvarchar(130)XA transaction branch qualifier.
XA_STATEvarchar(64)The state of the XA transaction. The value is ACTIVE (after XA START), IDLE (after XA END), PREPARED (after XA PREPARE), ROLLED BACK (after XA ROLLBACK), or COMMITTED (after XA COMMIT).
SOURCEvarchar(64)The name of the source file containing the instrumented code that produced the event and the line number in the file at which the instrumentation occurs.
TIMER_STARTbigint(20) unsignedThe unit is picoseconds. When event timing started. NULL if event has no timing information.
TIMER_ENDbigint(20) unsignedThe unit is picoseconds. When event timing ended. NULL if event has no timing information.
TIMER_WAITbigint(20) unsignedThe unit is picoseconds. Event duration. NULL if event has not timing information.
ACCESS_MODEenum('READ ONLY', 'READ WRITE')Transaction access mode.
ISOLATION_LEVELvarchar(64)Transaction isolation level. One of: REPEATABLE READ, READ COMMITTED, READ UNCOMMITTED, or SERIALIZABLE.
AUTOCOMMITenum('YES', 'NO')NO
NUMBER_OF_SAVEPOINTSbigint(20) unsignedThe number of SAVEPOINT statements issued during the transaction.
NUMBER_OF_ROLLBACK_TO_SAVEPOINTbigint(20) unsignedThe number of ROLLBACK_TO_SAVEPOINT statements issued during the transaction.
NUMBER_OF_RELEASE_SAVEPOINTbigint(20) unsignedThe number of RELEASE_SAVEPOINT statements issued during the transaction.
OBJECT_INSTANCE_BEGINbigint(20) unsignedUnused.
NESTING_EVENT_IDbigint(20) unsignedThe EVENT_ID value of the event within which this event is nested.
NESTING_EVENT_TYPEenum('TRANSACTION',' STATEMENT', 'STAGE', 'WAIT')The nesting event type.

1.1.1.2.9.2.1.23 Performance Schema events_transactions_history_long Table

MariaDB starting with 10.5.2

The events_transactions_history_long table was introduced in MariaDB 10.5.2.

The events_transactions_history_long table contains the most recent completed transaction events that have ended globally, across all threads.

The number of records stored in the table is determined by the performance_schema_events_transactions_history_long_size system variable, which is autosized on startup.

If adding a completed transaction would cause the table to exceed this limit, the oldest row, regardless of thread, is discarded.

The table contains the following columns:

ColumnTypeDescription
THREAD_IDbigint(20) unsignedThe thread associated with the event.
EVENT_IDbigint(20) unsignedThe event id associated with the event.
END_EVENT_IDbigint(20) unsignedThis column is set to NULL when the event starts and updated to the thread current event number when the event ends.
EVENT_NAMEvarchar(128)The name of the instrument from which the event was collected. This is a NAME value from the setup_instruments table.
STATEenum('ACTIVE', 'COMMITTED',' ROLLED BACK')The current transaction state. The value is ACTIVE (after START TRANSACTION or BEGIN), COMMITTED (after COMMIT), or ROLLED BACK (after ROLLBACK).
TRX_IDbigint(20) unsignedUnused.
GTIDvarchar(64)Transaction GTID, using the format DOMAIN-SERVER_ID-SEQUENCE_NO.
XID_FORMAT_IDint(11)XA transaction format ID for GTRID and BQUAL values.
XID_GTRIDvarchar(130)XA global transaction ID.
XID_BQUALvarchar(130)XA transaction branch qualifier.
XA_STATEvarchar(64)The state of the XA transaction. The value is ACTIVE (after XA START), IDLE (after XA END), PREPARED (after XA PREPARE), ROLLED BACK (after XA ROLLBACK), or COMMITTED (after XA COMMIT).
SOURCEvarchar(64)The name of the source file containing the instrumented code that produced the event and the line number in the file at which the instrumentation occurs.
TIMER_STARTbigint(20) unsignedThe unit is picoseconds. When event timing started. NULL if event has no timing information.
TIMER_ENDbigint(20) unsignedThe unit is picoseconds. When event timing ended. NULL if event has no timing information.
TIMER_WAITbigint(20) unsignedThe unit is picoseconds. Event duration. NULL if event has not timing information.
ACCESS_MODEenum('READ ONLY', 'READ WRITE')Transaction access mode.
ISOLATION_LEVELvarchar(64)Transaction isolation level. One of: REPEATABLE READ, READ COMMITTED, READ UNCOMMITTED, or SERIALIZABLE.
AUTOCOMMITenum('YES', 'NO')NO
NUMBER_OF_SAVEPOINTSbigint(20) unsignedThe number of SAVEPOINT statements issued during the transaction.
NUMBER_OF_ROLLBACK_TO_SAVEPOINTbigint(20) unsignedThe number of ROLLBACK_TO_SAVEPOINT statements issued during the transaction.
NUMBER_OF_RELEASE_SAVEPOINTbigint(20) unsignedThe number of RELEASE_SAVEPOINT statements issued during the transaction.
OBJECT_INSTANCE_BEGINbigint(20) unsignedUnused.
NESTING_EVENT_IDbigint(20) unsignedThe EVENT_ID value of the event within which this event is nested.
NESTING_EVENT_TYPEenum('TRANSACTION',' STATEMENT', 'STAGE', 'WAIT')The nesting event type.

1.1.1.2.9.2.1.24 Performance Schema events_transactions_summary_by_account_by_event_name Table

MariaDB starting with 10.5.2

The events_transactions_summary_by_account_by_event_name table was introduced in MariaDB 10.5.2.

The events_transactions_summary_by_account_by_event_name table contains information on transaction events aggregated by account and event name.

The table contains the following columns:

ColumnTypeDescription
USERchar(32)User for which summary is generated.
HOSTchar(60)Host for which summary is generated.
EVENT_NAMEvarchar(128)Event name for which summary is generated.
COUNT_STARbigint(20) unsignedThe number of summarized events. This value includes all events, whether timed or nontimed.
SUM_TIMER_WAITbigint(20) unsignedThe total wait time of the summarized timed events. This value is calculated only for timed events because nontimed events have a wait time of NULL. The same is true for the other xxx_TIMER_WAIT values.
MIN_TIMER_WAITbigint(20) unsignedThe minimum wait time of the summarized timed events.
AVG_TIMER_WAITbigint(20) unsignedThe average wait time of the summarized timed events.
MAX_TIMER_WAITbigint(20) unsignedThe maximum wait time of the summarized timed events.
COUNT_READ_WRITEbigint(20) unsignedThe total number of only READ/WRITE transaction events.
SUM_TIMER_READ_WRITEbigint(20) unsignedThe total wait time of only READ/WRITE transaction events.
MIN_TIMER_READ_WRITEbigint(20) unsignedThe minimum wait time of only READ/WRITE transaction events.
AVG_TIMER_READ_WRITEbigint(20) unsignedThe average wait time of only READ/WRITE transaction events.
MAX_TIMER_READ_WRITEbigint(20) unsignedThe maximum wait time of only READ/WRITE transaction events.
COUNT_READ_ONLYbigint(20) unsignedThe total number of only READ ONLY transaction events.
SUM_TIMER_READ_ONLYbigint(20) unsignedThe total wait time of only READ ONLY transaction events.
MIN_TIMER_READ_ONLYbigint(20) unsignedThe minimum wait time of only READ ONLY transaction events.
AVG_TIMER_READ_ONLYbigint(20) unsignedThe average wait time of only READ ONLY transaction events.
MAX_TIMER_READ_ONLYbigint(20) unsignedThe maximum wait time of only READ ONLY transaction events.

1.1.1.2.9.2.1.25 Performance Schema events_transactions_summary_by_host_by_event_name Table

MariaDB starting with 10.5.2

The events_transactions_summary_by_host_by_event_name table was introduced in MariaDB 10.5.2.

The events_transactions_summary_by_host_by_event_name table contains information on transaction events aggregated by host and event name.

The table contains the following columns:

ColumnTypeDescription
HOSTchar(60)Host for which summary is generated.
EVENT_NAMEvarchar(128)Event name for which summary is generated.
COUNT_STARbigint(20) unsignedThe number of summarized events. This value includes all events, whether timed or nontimed.
SUM_TIMER_WAITbigint(20) unsignedThe total wait time of the summarized timed events. This value is calculated only for timed events because nontimed events have a wait time of NULL. The same is true for the other xxx_TIMER_WAIT values.
MIN_TIMER_WAITbigint(20) unsignedThe minimum wait time of the summarized timed events.
AVG_TIMER_WAITbigint(20) unsignedThe average wait time of the summarized timed events.
MAX_TIMER_WAITbigint(20) unsignedThe maximum wait time of the summarized timed events.
COUNT_READ_WRITEbigint(20) unsignedThe total number of only READ/WRITE transaction events.
SUM_TIMER_READ_WRITEbigint(20) unsignedThe total wait time of only READ/WRITE transaction events.
MIN_TIMER_READ_WRITEbigint(20) unsignedThe minimum wait time of only READ/WRITE transaction events.
AVG_TIMER_READ_WRITEbigint(20) unsignedThe average wait time of only READ/WRITE transaction events.
MAX_TIMER_READ_WRITEbigint(20) unsignedThe maximum wait time of only READ/WRITE transaction events.
COUNT_READ_ONLYbigint(20) unsignedThe total number of only READ ONLY transaction events.
SUM_TIMER_READ_ONLYbigint(20) unsignedThe total wait time of only READ ONLY transaction events.
MIN_TIMER_READ_ONLYbigint(20) unsignedThe minimum wait time of only READ ONLY transaction events.
AVG_TIMER_READ_ONLYbigint(20) unsignedThe average wait time of only READ ONLY transaction events.
MAX_TIMER_READ_ONLYbigint(20) unsignedThe maximum wait time of only READ ONLY transaction events.

1.1.1.2.9.2.1.26 Performance Schema events_transactions_summary_by_thread_by_event_name Table

MariaDB starting with 10.5.2

The events_transactions_summary_by_thread_by_event_name table was introduced in MariaDB 10.5.2.

The events_transactions_summary_by_thread_by_event_name table contains information on transaction events aggregated by thread and event name.

The table contains the following columns:

+----------------------+---------------------+------+-----+---------+-------+
| Field                | Type                | Null | Key | Default | Extra |
+----------------------+---------------------+------+-----+---------+-------+
| THREAD_ID            | bigint(20) unsigned | NO   |     | NULL    |       |
| EVENT_NAME           | varchar(128)        | NO   |     | NULL    |       |
| COUNT_STAR           | bigint(20) unsigned | NO   |     | NULL    |       |
| SUM_TIMER_WAIT       | bigint(20) unsigned | NO   |     | NULL    |       |
| MIN_TIMER_WAIT       | bigint(20) unsigned | NO   |     | NULL    |       |
| AVG_TIMER_WAIT       | bigint(20) unsigned | NO   |     | NULL    |       |
| MAX_TIMER_WAIT       | bigint(20) unsigned | NO   |     | NULL    |       |
| COUNT_READ_WRITE     | bigint(20) unsigned | NO   |     | NULL    |       |
| SUM_TIMER_READ_WRITE | bigint(20) unsigned | NO   |     | NULL    |       |
| MIN_TIMER_READ_WRITE | bigint(20) unsigned | NO   |     | NULL    |       |
| AVG_TIMER_READ_WRITE | bigint(20) unsigned | NO   |     | NULL    |       |
| MAX_TIMER_READ_WRITE | bigint(20) unsigned | NO   |     | NULL    |       |
| COUNT_READ_ONLY      | bigint(20) unsigned | NO   |     | NULL    |       |
| SUM_TIMER_READ_ONLY  | bigint(20) unsigned | NO   |     | NULL    |       |
| MIN_TIMER_READ_ONLY  | bigint(20) unsigned | NO   |     | NULL    |       |
| AVG_TIMER_READ_ONLY  | bigint(20) unsigned | NO   |     | NULL    |       |
| MAX_TIMER_READ_ONLY  | bigint(20) unsigned | NO   |     | NULL    |       |
+----------------------+---------------------+------+-----+---------+-------+

1.1.1.2.9.2.1.27 Performance Schema events_transactions_summary_by_user_by_event_name Table

MariaDB starting with 10.5.2

The events_transactions_summary_by_user_by_event_name table was introduced in MariaDB 10.5.2.

The events_transactions_summary_by_user_by_event_name table contains information on transaction events aggregated by user and event name.

The table contains the following columns:

+----------------------+---------------------+------+-----+---------+-------+
| Field                | Type                | Null | Key | Default | Extra |
+----------------------+---------------------+------+-----+---------+-------+
| USER                 | char(32)            | YES  |     | NULL    |       |
| EVENT_NAME           | varchar(128)        | NO   |     | NULL    |       |
| COUNT_STAR           | bigint(20) unsigned | NO   |     | NULL    |       |
| SUM_TIMER_WAIT       | bigint(20) unsigned | NO   |     | NULL    |       |
| MIN_TIMER_WAIT       | bigint(20) unsigned | NO   |     | NULL    |       |
| AVG_TIMER_WAIT       | bigint(20) unsigned | NO   |     | NULL    |       |
| MAX_TIMER_WAIT       | bigint(20) unsigned | NO   |     | NULL    |       |
| COUNT_READ_WRITE     | bigint(20) unsigned | NO   |     | NULL    |       |
| SUM_TIMER_READ_WRITE | bigint(20) unsigned | NO   |     | NULL    |       |
| MIN_TIMER_READ_WRITE | bigint(20) unsigned | NO   |     | NULL    |       |
| AVG_TIMER_READ_WRITE | bigint(20) unsigned | NO   |     | NULL    |       |
| MAX_TIMER_READ_WRITE | bigint(20) unsigned | NO   |     | NULL    |       |
| COUNT_READ_ONLY      | bigint(20) unsigned | NO   |     | NULL    |       |
| SUM_TIMER_READ_ONLY  | bigint(20) unsigned | NO   |     | NULL    |       |
| MIN_TIMER_READ_ONLY  | bigint(20) unsigned | NO   |     | NULL    |       |
| AVG_TIMER_READ_ONLY  | bigint(20) unsigned | NO   |     | NULL    |       |
| MAX_TIMER_READ_ONLY  | bigint(20) unsigned | NO   |     | NULL    |       |
+----------------------+---------------------+------+-----+---------+-------+

1.1.1.2.9.2.1.28 Performance Schema events_transactions_summary_global_by_event_name Table

MariaDB starting with 10.5.2

The events_transactions_summary_global_by_event_name table was introduced in MariaDB 10.5.2.

The events_transactions_summary_global_by_event_name table contains information on transaction events aggregated by event name.

The table contains the following columns:

+----------------------+---------------------+------+-----+---------+-------+
| Field                | Type                | Null | Key | Default | Extra |
+----------------------+---------------------+------+-----+---------+-------+
| EVENT_NAME           | varchar(128)        | NO   |     | NULL    |       |
| COUNT_STAR           | bigint(20) unsigned | NO   |     | NULL    |       |
| SUM_TIMER_WAIT       | bigint(20) unsigned | NO   |     | NULL    |       |
| MIN_TIMER_WAIT       | bigint(20) unsigned | NO   |     | NULL    |       |
| AVG_TIMER_WAIT       | bigint(20) unsigned | NO   |     | NULL    |       |
| MAX_TIMER_WAIT       | bigint(20) unsigned | NO   |     | NULL    |       |
| COUNT_READ_WRITE     | bigint(20) unsigned | NO   |     | NULL    |       |
| SUM_TIMER_READ_WRITE | bigint(20) unsigned | NO   |     | NULL    |       |
| MIN_TIMER_READ_WRITE | bigint(20) unsigned | NO   |     | NULL    |       |
| AVG_TIMER_READ_WRITE | bigint(20) unsigned | NO   |     | NULL    |       |
| MAX_TIMER_READ_WRITE | bigint(20) unsigned | NO   |     | NULL    |       |
| COUNT_READ_ONLY      | bigint(20) unsigned | NO   |     | NULL    |       |
| SUM_TIMER_READ_ONLY  | bigint(20) unsigned | NO   |     | NULL    |       |
| MIN_TIMER_READ_ONLY  | bigint(20) unsigned | NO   |     | NULL    |       |
| AVG_TIMER_READ_ONLY  | bigint(20) unsigned | NO   |     | NULL    |       |
| MAX_TIMER_READ_ONLY  | bigint(20) unsigned | NO   |     | NULL    |       |
+----------------------+---------------------+------+-----+---------+-------+

1.1.1.2.9.2.1.29 Performance Schema events_waits_current Table

The events_waits_current table contains the status of a thread's most recently monitored wait event, listing one event per thread.

The table contains the following columns:

ColumnDescription
THREAD_IDThread associated with the event. Together with EVENT_ID uniquely identifies the row.
EVENT_IDThread's current event number at the start of the event. Together with THREAD_ID uniquely identifies the row.
END_EVENT_IDNULL when the event starts, set to the thread's current event number at the end of the event.
EVENT_NAMEEvent instrument name and a NAME from the setup_instruments table
SOURCEName and line number of the source file containing the instrumented code that produced the event.
TIMER_STARTValue in picoseconds when the event timing started or NULL if timing is not collected.
TIMER_ENDValue in picoseconds when the event timing ended, or NULL if the event has not ended or timing is not collected.
TIMER_WAITValue in picoseconds of the event's duration or NULL if the event has not ended or timing is not collected.
SPINSNumber of spin rounds for a mutex, or NULL if spin rounds are not used, or spinning is not instrumented.
OBJECT_SCHEMAName of the schema that contains the table for table I/O objects, otherwise NULL for file I/O and synchronization objects.
OBJECT_NAMEFile name for file I/O objects, table name for table I/O objects, the socket's IP:PORT value for a socket object or NULL for a synchronization object.
INDEX NAMEName of the index, PRIMARY for the primary key, or NULL for no index used.
OBJECT_TYPEFILE for a file object, TABLE or TEMPORARY TABLE for a table object, or NULL for a synchronization object.
OBJECT_INSTANCE_BEGINAddress in memory of the object.
NESTING_EVENT_IDEVENT_ID of event within which this event nests.
NESTING_EVENT_TYPENesting event type. Either statement, stage or wait.
OPERATIONOperation type, for example read, write or lock
NUMBER_OF_BYTESNumber of bytes that the operation read or wrote, or NULL for table I/O waits.
FLAGSReserved for use in the future.

It is possible to empty this table with a TRUNCATE TABLE statement.

The related tables, events_waits_history and events_waits_history_long derive their values from the current events.

1.1.1.2.9.2.1.30 Performance Schema events_waits_history Table

The events_waits_history table by default contains the ten most recent completed wait events per thread. This number can be adjusted by setting the performance_schema_events_waits_history_size system variable when the server starts up.

The table structure is identical to the events_waits_current table structure, and contains the following columns:

ColumnDescription
THREAD_IDThread associated with the event. Together with EVENT_ID uniquely identifies the row.
EVENT_IDThread's current event number at the start of the event. Together with THREAD_ID uniquely identifies the row.
END_EVENT_IDNULL when the event starts, set to the thread's current event number at the end of the event.
EVENT_NAMEEvent instrument name and a NAME from the setup_instruments table
SOURCEName and line number of the source file containing the instrumented code that produced the event.
TIMER_STARTValue in picoseconds when the event timing started or NULL if timing is not collected.
TIMER_ENDValue in picoseconds when the event timing ended, or NULL if timing is not collected.
TIMER_WAITValue in picoseconds of the event's duration or NULL if timing is not collected.
SPINSNumber of spin rounds for a mutex, or NULL if spin rounds are not used, or spinning is not instrumented.
OBJECT_SCHEMAName of the schema that contains the table for table I/O objects, otherwise NULL for file I/O and synchronization objects.
OBJECT_NAMEFile name for file I/O objects, table name for table I/O objects, the socket's IP:PORT value for a socket object or NULL for a synchronization object.
INDEX NAMEName of the index, PRIMARY for the primary key, or NULL for no index used.
OBJECT_TYPEFILE for a file object, TABLE or TEMPORARY TABLE for a table object, or NULL for a synchronization object.
OBJECT_INSTANCE_BEGINAddress in memory of the object.
NESTING_EVENT_IDEVENT_ID of event within which this event nests.
NESTING_EVENT_TYPENesting event type. Either statement, stage or wait.
OPERATIONOperation type, for example read, write or lock
NUMBER_OF_BYTESNumber of bytes that the operation read or wrote, or NULL for table I/O waits.
FLAGSReserved for use in the future.

It is possible to empty this table with a TRUNCATE TABLE statement.

events_waits_current and events_waits_history_long are related tables.

1.1.1.2.9.2.1.31 Performance Schema events_waits_summary_by_account_by_event_name Table

The Performance Schema events_waits_summary_by_account_by_event_name table contains wait events summarized by account and event name. It contains the following columns:

ColumnDescription
USERUser. Used together with HOST and EVENT_NAME for grouping events.
HOSTHost. Used together with USER and EVENT_NAME for grouping events.
EVENT_NAMEEvent name. Used together with USER and HOST for grouping events.
COUNT_STARNumber of summarized events
SUM_TIMER_WAITTotal wait time of the summarized events that are timed.
MIN_TIMER_WAITMinimum wait time of the summarized events that are timed.
AVG_TIMER_WAITAverage wait time of the summarized events that are timed.
MAX_TIMER_WAITMaximum wait time of the summarized events that are timed.

The *_TIMER_WAIT columns only calculate results for timed events, as non-timed events have a NULL wait time.

Example

SELECT * FROM events_waits_summary_by_account_by_event_name\G
...
*************************** 915. row ***************************
          USER: NULL
          HOST: NULL
    EVENT_NAME: wait/io/socket/sql/server_tcpip_socket
    COUNT_STAR: 0
SUM_TIMER_WAIT: 0
MIN_TIMER_WAIT: 0
AVG_TIMER_WAIT: 0
MAX_TIMER_WAIT: 0
*************************** 916. row ***************************
          USER: NULL
          HOST: NULL
    EVENT_NAME: wait/io/socket/sql/server_unix_socket
    COUNT_STAR: 0
SUM_TIMER_WAIT: 0
MIN_TIMER_WAIT: 0
AVG_TIMER_WAIT: 0
MAX_TIMER_WAIT: 0
*************************** 917. row ***************************
          USER: NULL
          HOST: NULL
    EVENT_NAME: wait/io/socket/sql/client_connection
    COUNT_STAR: 0
SUM_TIMER_WAIT: 0
MIN_TIMER_WAIT: 0
AVG_TIMER_WAIT: 0
MAX_TIMER_WAIT: 0
*************************** 918. row ***************************
          USER: NULL
          HOST: NULL
    EVENT_NAME: idle
    COUNT_STAR: 0
SUM_TIMER_WAIT: 0
MIN_TIMER_WAIT: 0
AVG_TIMER_WAIT: 0
MAX_TIMER_WAIT: 0

1.1.1.2.9.2.1.32 Performance Schema events_waits_summary_by_host_by_event_name Table

The Performance Schema events_waits_summary_by_host_by_event_name table contains wait events summarized by host and event name. It contains the following columns:

ColumnDescription
HOSTHost. Used together with EVENT_NAME for grouping events.
EVENT_NAMEEvent name. Used together with USER and HOST for grouping events.
COUNT_STARNumber of summarized events
SUM_TIMER_WAITTotal wait time of the summarized events that are timed.
MIN_TIMER_WAITMinimum wait time of the summarized events that are timed.
AVG_TIMER_WAITAverage wait time of the summarized events that are timed.
MAX_TIMER_WAITMaximum wait time of the summarized events that are timed.

The *_TIMER_WAIT columns only calculate results for timed events, as non-timed events have a NULL wait time.

Example

SELECT * FROM events_waits_summary_by_host_by_event_name\G
...
*************************** 610. row ***************************
          HOST: NULL
    EVENT_NAME: wait/io/socket/sql/server_unix_socket
    COUNT_STAR: 0
SUM_TIMER_WAIT: 0
MIN_TIMER_WAIT: 0
AVG_TIMER_WAIT: 0
MAX_TIMER_WAIT: 0
*************************** 611. row ***************************
          HOST: NULL
    EVENT_NAME: wait/io/socket/sql/client_connection
    COUNT_STAR: 0
SUM_TIMER_WAIT: 0
MIN_TIMER_WAIT: 0
AVG_TIMER_WAIT: 0
MAX_TIMER_WAIT: 0
*************************** 612. row ***************************
          HOST: NULL
    EVENT_NAME: idle
    COUNT_STAR: 0
SUM_TIMER_WAIT: 0
MIN_TIMER_WAIT: 0
AVG_TIMER_WAIT: 0
MAX_TIMER_WAIT: 0

1.1.1.2.9.2.1.33 Performance Schema events_waits_summary_by_instance Table

The Performance Schema events_waits_summary_by_instance table contains wait events summarized by instance. It contains the following columns:

ColumnDescription
EVENT_NAMEEvent name. Used together with OBJECT_INSTANCE_BEGIN for grouping events.
OBJECT_INSTANCE_BEGINIf an instrument creates multiple instances, each instance has a unique OBJECT_INSTANCE_BEGIN value to allow for grouping by instance.
COUNT_STARNumber of summarized events
SUM_TIMER_WAITTotal wait time of the summarized events that are timed.
MIN_TIMER_WAITMinimum wait time of the summarized events that are timed.
AVG_TIMER_WAITAverage wait time of the summarized events that are timed.
MAX_TIMER_WAITMaximum wait time of the summarized events that are timed.

The *_TIMER_WAIT columns only calculate results for timed events, as non-timed events have a NULL wait time.

Example

SELECT * FROM events_waits_summary_by_instance\G
...
*************************** 202. row ***************************
           EVENT_NAME: wait/io/file/sql/binlog
OBJECT_INSTANCE_BEGIN: 140578961969856
           COUNT_STAR: 6
       SUM_TIMER_WAIT: 90478331960
       MIN_TIMER_WAIT: 263344
       AVG_TIMER_WAIT: 15079721848
       MAX_TIMER_WAIT: 67760576376
*************************** 203. row ***************************
           EVENT_NAME: wait/io/file/sql/dbopt
OBJECT_INSTANCE_BEGIN: 140578961970560
           COUNT_STAR: 6
       SUM_TIMER_WAIT: 39891428472
       MIN_TIMER_WAIT: 387168
       AVG_TIMER_WAIT: 6648571412
       MAX_TIMER_WAIT: 24503293304
*************************** 204. row ***************************
           EVENT_NAME: wait/io/file/sql/dbopt
OBJECT_INSTANCE_BEGIN: 140578961971264
           COUNT_STAR: 6
       SUM_TIMER_WAIT: 39902495024
       MIN_TIMER_WAIT: 177888
       AVG_TIMER_WAIT: 6650415692
       MAX_TIMER_WAIT: 21026400404

1.1.1.2.9.2.1.34 Performance Schema events_waits_summary_by_thread_by_event_name Table

The Performance Schema events_waits_summary_by_thread_by_event_name table contains wait events summarized by thread and event name. It contains the following columns:

ColumnDescription
THREAD_IDThread associated with the event. Together with EVENT_NAME uniquely identifies the row.
EVENT_NAMEEvent name. Used together with THREAD_ID for grouping events.
COUNT_STARNumber of summarized events
SUM_TIMER_WAITTotal wait time of the summarized events that are timed.
MIN_TIMER_WAITMinimum wait time of the summarized events that are timed.
AVG_TIMER_WAITAverage wait time of the summarized events that are timed.
MAX_TIMER_WAITMaximum wait time of the summarized events that are timed.

The *_TIMER_WAIT columns only calculate results for timed events, as non-timed events have a NULL wait time.

Example

SELECT * FROM events_waits_summary_by_thread_by_event_name\G
...
*************************** 6424. row ***************************
     THREAD_ID: 64
    EVENT_NAME: wait/io/socket/sql/server_unix_socket
    COUNT_STAR: 0
SUM_TIMER_WAIT: 0
MIN_TIMER_WAIT: 0
AVG_TIMER_WAIT: 0
MAX_TIMER_WAIT: 0
*************************** 6425. row ***************************
     THREAD_ID: 64
    EVENT_NAME: wait/io/socket/sql/client_connection
    COUNT_STAR: 0
SUM_TIMER_WAIT: 0
MIN_TIMER_WAIT: 0
AVG_TIMER_WAIT: 0
MAX_TIMER_WAIT: 0
*************************** 6426. row ***************************
     THREAD_ID: 64
    EVENT_NAME: idle
    COUNT_STAR: 73
SUM_TIMER_WAIT: 22005252162000000
MIN_TIMER_WAIT: 3000000
AVG_TIMER_WAIT: 301441810000000
MAX_TIMER_WAIT: 4912417573000000

1.1.1.2.9.2.1.35 Performance Schema events_waits_summary_by_user_by_event_name Table

The Performance Schema events_waits_summary_by_user_by_event_name table contains wait events summarized by user and event name. It contains the following columns:

ColumnDescription
USERUser. Used together with EVENT_NAME for grouping events.
EVENT_NAMEEvent name. Used together with USER for grouping events.
COUNT_STARNumber of summarized events
SUM_TIMER_WAITTotal wait time of the summarized events that are timed.
MIN_TIMER_WAITMinimum wait time of the summarized events that are timed.
AVG_TIMER_WAITAverage wait time of the summarized events that are timed.
MAX_TIMER_WAITMaximum wait time of the summarized events that are timed.

The *_TIMER_WAIT columns only calculate results for timed events, as non-timed events have a NULL wait time.

Example

SELECT * FROM events_waits_summary_by_user_by_event_name\G
...
*************************** 916. row ***************************
          USER: NULL
    EVENT_NAME: wait/io/socket/sql/server_unix_socket
    COUNT_STAR: 0
SUM_TIMER_WAIT: 0
MIN_TIMER_WAIT: 0
AVG_TIMER_WAIT: 0
MAX_TIMER_WAIT: 0
*************************** 917. row ***************************
          USER: NULL
    EVENT_NAME: wait/io/socket/sql/client_connection
    COUNT_STAR: 0
SUM_TIMER_WAIT: 0
MIN_TIMER_WAIT: 0
AVG_TIMER_WAIT: 0
MAX_TIMER_WAIT: 0
*************************** 918. row ***************************
          USER: NULL
    EVENT_NAME: idle
    COUNT_STAR: 0
SUM_TIMER_WAIT: 0
MIN_TIMER_WAIT: 0
AVG_TIMER_WAIT: 0
MAX_TIMER_WAIT: 0

1.1.1.2.9.2.1.36 Performance Schema events_waits_summary_global_by_event_name Table

The Performance Schema events_waits_summary_global_by_event_name table contains wait events summarized by event name. It contains the following columns:

ColumnDescription
EVENT_NAMEEvent name.
COUNT_STARNumber of summarized events
SUM_TIMER_WAITTotal wait time of the summarized events that are timed.
MIN_TIMER_WAITMinimum wait time of the summarized events that are timed.
AVG_TIMER_WAITAverage wait time of the summarized events that are timed.
MAX_TIMER_WAITMaximum wait time of the summarized events that are timed.

The *_TIMER_WAIT columns only calculate results for timed events, as non-timed events have a NULL wait time.

Example

SELECT * FROM events_waits_summary_global_by_event_name\G
...
*************************** 303. row ***************************
    EVENT_NAME: wait/io/socket/sql/server_tcpip_socket
    COUNT_STAR: 0
SUM_TIMER_WAIT: 0
MIN_TIMER_WAIT: 0
AVG_TIMER_WAIT: 0
MAX_TIMER_WAIT: 0
*************************** 304. row ***************************
    EVENT_NAME: wait/io/socket/sql/server_unix_socket
    COUNT_STAR: 0
SUM_TIMER_WAIT: 0
MIN_TIMER_WAIT: 0
AVG_TIMER_WAIT: 0
MAX_TIMER_WAIT: 0
*************************** 305. row ***************************
    EVENT_NAME: wait/io/socket/sql/client_connection
    COUNT_STAR: 0
SUM_TIMER_WAIT: 0
MIN_TIMER_WAIT: 0
AVG_TIMER_WAIT: 0
MAX_TIMER_WAIT: 0
*************************** 306. row ***************************
    EVENT_NAME: idle
    COUNT_STAR: 265
SUM_TIMER_WAIT: 46861125181000000
MIN_TIMER_WAIT: 1000000
AVG_TIMER_WAIT: 176834434000000
MAX_TIMER_WAIT: 4912417573000000

1.1.1.2.9.2.1.37 Performance Schema file_instances Table

Description

The file_instances table lists instances of instruments seen by the Performance Schema when executing file I/O instrumentation, and the associated files. Only files that have been opened, and that have not been deleted, will be listed in the table.

The performance_schema_max_file_instances system variable specifies the maximum number of instrumented file objects.

ColumnDescription
FILE_NAMEFile name.
EVENT_NAMEInstrument name associated with the file.
OPEN_COUNTOpen handles on the file. A value of greater than zero means that the file is currently open.

Example

SELECT * FROM performance_schema.file_instances WHERE OPEN_COUNT>0;
+----------------------------------------------------+--------------------------------------+------------+
| FILE_NAME                                          | EVENT_NAME                           | OPEN_COUNT |
+----------------------------------------------------+--------------------------------------+------------+
| /var/log/mysql/mariadb-bin.index                   | wait/io/file/sql/binlog_index        |          1 |
| /var/lib/mysql/ibdata1                             | wait/io/file/innodb/innodb_data_file |          2 |
| /var/lib/mysql/ib_logfile0                         | wait/io/file/innodb/innodb_log_file  |          2 |
| /var/lib/mysql/ib_logfile1                         | wait/io/file/innodb/innodb_log_file  |          2 |
| /var/lib/mysql/mysql/gtid_slave_pos.ibd            | wait/io/file/innodb/innodb_data_file |          3 |
| /var/lib/mysql/mysql/innodb_index_stats.ibd        | wait/io/file/innodb/innodb_data_file |          3 |
| /var/lib/mysql/mysql/innodb_table_stats.ibd        | wait/io/file/innodb/innodb_data_file |          3 |
...

1.1.1.2.9.2.1.38 Performance Schema file_summary_by_event_name Table

The Performance Schema file_summary_by_event_name table contains file events summarized by event name. It contains the following columns:

ColumnDescription
EVENT_NAMEEvent name.
COUNT_STARNumber of summarized events
SUM_TIMER_WAITTotal wait time of the summarized events that are timed.
MIN_TIMER_WAITMinimum wait time of the summarized events that are timed.
AVG_TIMER_WAITAverage wait time of the summarized events that are timed.
MAX_TIMER_WAITMaximum wait time of the summarized events that are timed.
COUNT_READNumber of all read operations, including FGETS, FGETC, FREAD, and READ.
SUM_TIMER_READTotal wait time of all read operations that are timed.
MIN_TIMER_READMinimum wait time of all read operations that are timed.
AVG_TIMER_READAverage wait time of all read operations that are timed.
MAX_TIMER_READMaximum wait time of all read operations that are timed.
SUM_NUMBER_OF_BYTES_READBytes read by read operations.
COUNT_WRITENumber of all write operations, including FPUTS, FPUTC, FPRINTF, VFPRINTF, FWRITE, and PWRITE.
SUM_TIMER_WRITETotal wait time of all write operations that are timed.
MIN_TIMER_WRITEMinimum wait time of all write operations that are timed.
AVG_TIMER_WRITEAverage wait time of all write operations that are timed.
MAX_TIMER_WRITEMaximum wait time of all write operations that are timed.
SUM_NUMBER_OF_BYTES_WRITEBytes written by write operations.
COUNT_MISCNumber of all miscellaneous operations not counted above, including CREATE, DELETE, OPEN, CLOSE, STREAM_OPEN, STREAM_CLOSE, SEEK, TELL, FLUSH, STAT, FSTAT, CHSIZE, RENAME, and SYNC.
SUM_TIMER_MISCTotal wait time of all miscellaneous operations that are timed.
MIN_TIMER_MISCMinimum wait time of all miscellaneous operations that are timed.
AVG_TIMER_MISCAverage wait time of all miscellaneous operations that are timed.
MAX_TIMER_MISCMaximum wait time of all miscellaneous operations that are timed.

I/O operations can be avoided by caching, in which case they will not be recorded in this table.

You can TRUNCATE the table, which will reset all counters to zero.

Example

SELECT * FROM file_summary_by_event_name\G
...
*************************** 49. row ***************************
               EVENT_NAME: wait/io/file/aria/MAD
               COUNT_STAR: 60
           SUM_TIMER_WAIT: 397234368
           MIN_TIMER_WAIT: 0
           AVG_TIMER_WAIT: 6620224
           MAX_TIMER_WAIT: 16808672
               COUNT_READ: 0
           SUM_TIMER_READ: 0
           MIN_TIMER_READ: 0
           AVG_TIMER_READ: 0
           MAX_TIMER_READ: 0
 SUM_NUMBER_OF_BYTES_READ: 0
              COUNT_WRITE: 0
          SUM_TIMER_WRITE: 0
          MIN_TIMER_WRITE: 0
          AVG_TIMER_WRITE: 0
          MAX_TIMER_WRITE: 0
SUM_NUMBER_OF_BYTES_WRITE: 0
               COUNT_MISC: 60
           SUM_TIMER_MISC: 397234368
           MIN_TIMER_MISC: 0
           AVG_TIMER_MISC: 6620224
           MAX_TIMER_MISC: 16808672
*************************** 50. row ***************************
               EVENT_NAME: wait/io/file/aria/control
               COUNT_STAR: 3
           SUM_TIMER_WAIT: 24055778544
           MIN_TIMER_WAIT: 0
           AVG_TIMER_WAIT: 8018592848
           MAX_TIMER_WAIT: 24027262400
               COUNT_READ: 1
           SUM_TIMER_READ: 24027262400
           MIN_TIMER_READ: 0
           AVG_TIMER_READ: 24027262400
           MAX_TIMER_READ: 24027262400
 SUM_NUMBER_OF_BYTES_READ: 52
              COUNT_WRITE: 0
          SUM_TIMER_WRITE: 0
          MIN_TIMER_WRITE: 0
          AVG_TIMER_WRITE: 0
          MAX_TIMER_WRITE: 0
SUM_NUMBER_OF_BYTES_WRITE: 0
               COUNT_MISC: 2
           SUM_TIMER_MISC: 28516144
           MIN_TIMER_MISC: 0
           AVG_TIMER_MISC: 14258072
           MAX_TIMER_MISC: 27262208

1.1.1.2.9.2.1.39 Performance Schema file_summary_by_instance Table

The Performance Schema file_summary_by_instance table contains file events summarized by instance. It contains the following columns:

ColumnDescription
FILE_NAMEFile name.
EVENT_NAMEEvent name.
OBJECT_INSTANCE_BEGINAddress in memory. Together with FILE_NAME and EVENT_NAME uniquely identifies a row.
COUNT_STARNumber of summarized events
SUM_TIMER_WAITTotal wait time of the summarized events that are timed.
MIN_TIMER_WAITMinimum wait time of the summarized events that are timed.
AVG_TIMER_WAITAverage wait time of the summarized events that are timed.
MAX_TIMER_WAITMaximum wait time of the summarized events that are timed.
COUNT_READNumber of all read operations, including FGETS, FGETC, FREAD, and READ.
SUM_TIMER_READTotal wait time of all read operations that are timed.
MIN_TIMER_READMinimum wait time of all read operations that are timed.
AVG_TIMER_READAverage wait time of all read operations that are timed.
MAX_TIMER_READMaximum wait time of all read operations that are timed.
SUM_NUMBER_OF_BYTES_READBytes read by read operations.
COUNT_WRITENumber of all write operations, including FPUTS, FPUTC, FPRINTF, VFPRINTF, FWRITE, and PWRITE.
SUM_TIMER_WRITETotal wait time of all write operations that are timed.
MIN_TIMER_WRITEMinimum wait time of all write operations that are timed.
AVG_TIMER_WRITEAverage wait time of all write operations that are timed.
MAX_TIMER_WRITEMaximum wait time of all write operations that are timed.
SUM_NUMBER_OF_BYTES_WRITEBytes written by write operations.
COUNT_MISCNumber of all miscellaneous operations not counted above, including CREATE, DELETE, OPEN, CLOSE, STREAM_OPEN, STREAM_CLOSE, SEEK, TELL, FLUSH, STAT, FSTAT, CHSIZE, RENAME, and SYNC.
SUM_TIMER_MISCTotal wait time of all miscellaneous operations that are timed.
MIN_TIMER_MISCMinimum wait time of all miscellaneous operations that are timed.
AVG_TIMER_MISCAverage wait time of all miscellaneous operations that are timed.
MAX_TIMER_MISCMaximum wait time of all miscellaneous operations that are timed.

I/O operations can be avoided by caching, in which case they will not be recorded in this table.

You can TRUNCATE the table, which will reset all counters to zero.

Example

SELECT * FROM file_summary_by_instance\G
...
*************************** 204. row ***************************
                FILE_NAME: /var/lib/mysql/test/db.opt
               EVENT_NAME: wait/io/file/sql/dbopt
    OBJECT_INSTANCE_BEGIN: 140578961971264
               COUNT_STAR: 6
           SUM_TIMER_WAIT: 39902495024
           MIN_TIMER_WAIT: 177888
           AVG_TIMER_WAIT: 6650415692
           MAX_TIMER_WAIT: 21026400404
               COUNT_READ: 1
           SUM_TIMER_READ: 21026400404
           MIN_TIMER_READ: 21026400404
           AVG_TIMER_READ: 21026400404
           MAX_TIMER_READ: 21026400404
 SUM_NUMBER_OF_BYTES_READ: 65
              COUNT_WRITE: 0
          SUM_TIMER_WRITE: 0
          MIN_TIMER_WRITE: 0
          AVG_TIMER_WRITE: 0
          MAX_TIMER_WRITE: 0
SUM_NUMBER_OF_BYTES_WRITE: 0
               COUNT_MISC: 5
           SUM_TIMER_MISC: 18876094620
           MIN_TIMER_MISC: 177888
           AVG_TIMER_MISC: 3775218924
           MAX_TIMER_MISC: 18864558060
*************************** 205. row ***************************
                FILE_NAME: /var/log/mysql/mariadb-bin.000157
               EVENT_NAME: wait/io/file/sql/binlog
    OBJECT_INSTANCE_BEGIN: 140578961971968
               COUNT_STAR: 6
           SUM_TIMER_WAIT: 73985877680
           MIN_TIMER_WAIT: 251136
           AVG_TIMER_WAIT: 12330979468
           MAX_TIMER_WAIT: 73846656340
               COUNT_READ: 0
           SUM_TIMER_READ: 0
           MIN_TIMER_READ: 0
           AVG_TIMER_READ: 0
           MAX_TIMER_READ: 0
 SUM_NUMBER_OF_BYTES_READ: 0
              COUNT_WRITE: 2
          SUM_TIMER_WRITE: 62583004
          MIN_TIMER_WRITE: 27630192
          AVG_TIMER_WRITE: 31291284
          MAX_TIMER_WRITE: 34952812
SUM_NUMBER_OF_BYTES_WRITE: 369
               COUNT_MISC: 4
           SUM_TIMER_MISC: 73923294676
           MIN_TIMER_MISC: 251136
           AVG_TIMER_MISC: 18480823560
           MAX_TIMER_MISC: 73846656340

1.1.1.2.9.2.1.40 Performance Schema global_status Table

MariaDB starting with 10.5.2

The global_status table was added in MariaDB 10.5.2.

The global_status table contains a list of status variables and their global values. The table only stores status variable statistics for threads which are instrumented, and does not collect statistics for Com_xxx variables.

The table contains the following columns:

ColumnDescription
VARIABLE_NAMEThe global status variable name.
VARIABLE_VALUEThe global status variable value.

TRUNCATE TABLE resets global status variables, including thread, account, host, and user status, but not those that are never reset by the server.

1.1.1.2.9.2.1.41 Performance Schema hosts Table

Description

The hosts table contains a row for each host used by clients to connect to the server, containing current and total connections.

The size is determined by the performance_schema_hosts_size system variable, which, if set to zero, will disable connection statistics in the hosts table.

It contains the following columns:

ColumnDescription
HOSTHost name used by the client to connect, NULL for internal threads or user sessions that failed to authenticate.
CURRENT_CONNECTIONSCurrent number of the host's connections.
TOTAL_CONNECTIONSTotal number of the host's connections

Example

SELECT * FROM hosts;
+-----------+---------------------+-------------------+
| HOST      | CURRENT_CONNECTIONS | TOTAL_CONNECTIONS |
+-----------+---------------------+-------------------+
| localhost |                   1 |                45 |
| NULL      |                  20 |                23 |
+-----------+---------------------+-------------------+

1.1.1.2.9.2.1.42 Performance Schema memory_summary_by_account_by_event_name Table

MariaDB starting with 10.5.2

The memory_summary_by_account_by_event_name table was introduced in MariaDB 10.5.2.

There are five memory summary tables in the Performance Schema that share a number of fields in common. These include:

The memory_summary_by_account_by_event_name table contains memory usage statistics aggregated by account and event.

The table contains the following columns:

FieldTypeNullDefaultDescription
USERchar(32)YESNULLUser portion of the account.
HOSTchar(60)YESNULLHost portion of the account.
EVENT_NAMEvarchar(128)NONULLEvent name.
COUNT_ALLOCbigint(20) unsignedNONULLTotal number of allocations to memory.
COUNT_FREEbigint(20) unsignedNONULLTotal number of attempts to free the allocated memory.
SUM_NUMBER_OF_BYTES_ALLOCbigint(20) unsignedNONULLTotal number of bytes allocated.
SUM_NUMBER_OF_BYTES_FREEbigint(20) unsignedNONULLTotal number of bytes freed
LOW_COUNT_USEDbigint(20)NONULLLowest number of allocated blocks (lowest value of CURRENT_COUNT_USED).
CURRENT_COUNT_USEDbigint(20)NONULLCurrently allocated blocks that have not been freed (COUNT_ALLOC minus COUNT_FREE).
HIGH_COUNT_USEDbigint(20)NONULLHighest number of allocated blocks (highest value of CURRENT_COUNT_USED).
LOW_NUMBER_OF_BYTES_USEDbigint(20)NONULLLowest number of bytes used.
CURRENT_NUMBER_OF_BYTES_USEDbigint(20)NONULLCurrent number of bytes used (total allocated minus total freed).
HIGH_NUMBER_OF_BYTES_USEDbigint(20)NONULLHighest number of bytes used.

1.1.1.2.9.2.1.43 Performance Schema memory_summary_by_host_by_event_name Table

MariaDB starting with 10.5.2

The memory_summary_by_host_by_event_name table was introduced in MariaDB 10.5.2.

There are five memory summary tables in the Performance Schema that share a number of fields in common. These include:

The memory_summary_by_host_by_event_name table contains memory usage statistics aggregated by host and event.

The table contains the following columns:

FieldTypeNullDefaultDescription
HOSTchar(60)YESNULLHost portion of the account.
EVENT_NAMEvarchar(128)NONULLEvent name.
COUNT_ALLOCbigint(20) unsignedNONULLTotal number of allocations to memory.
COUNT_FREEbigint(20) unsignedNONULLTotal number of attempts to free the allocated memory.
SUM_NUMBER_OF_BYTES_ALLOCbigint(20) unsignedNONULLTotal number of bytes allocated.
SUM_NUMBER_OF_BYTES_FREEbigint(20) unsignedNONULLTotal number of bytes freed
LOW_COUNT_USEDbigint(20)NONULLLowest number of allocated blocks (lowest value of CURRENT_COUNT_USED).
CURRENT_COUNT_USEDbigint(20)NONULLCurrently allocated blocks that have not been freed (COUNT_ALLOC minus COUNT_FREE).
HIGH_COUNT_USEDbigint(20)NONULLHighest number of allocated blocks (highest value of CURRENT_COUNT_USED).
LOW_NUMBER_OF_BYTES_USEDbigint(20)NONULLLowest number of bytes used.
CURRENT_NUMBER_OF_BYTES_USEDbigint(20)NONULLCurrent number of bytes used (total allocated minus total freed).
HIGH_NUMBER_OF_BYTES_USEDbigint(20)NONULLHighest number of bytes used.

1.1.1.2.9.2.1.44 Performance Schema memory_summary_by_thread_by_event_name Table

MariaDB starting with 10.5.2

The memory_summary_by_thread_by_event_name table was introduced in MariaDB 10.5.2.

There are five memory summary tables in the Performance Schema that share a number of fields in common. These include:

The memory_summary_by_thread_by_event_name table contains memory usage statistics aggregated by thread and event.

The table contains the following columns:

FieldTypeNullDefaultDescription
THREAD_IDbigint(20) unsignedNONULLThread id.
EVENT_NAMEvarchar(128)NONULLEvent name.
COUNT_ALLOCbigint(20) unsignedNONULLTotal number of allocations to memory.
COUNT_FREEbigint(20) unsignedNONULLTotal number of attempts to free the allocated memory.
SUM_NUMBER_OF_BYTES_ALLOCbigint(20) unsignedNONULLTotal number of bytes allocated.
SUM_NUMBER_OF_BYTES_FREEbigint(20) unsignedNONULLTotal number of bytes freed
LOW_COUNT_USEDbigint(20)NONULLLowest number of allocated blocks (lowest value of CURRENT_COUNT_USED).
CURRENT_COUNT_USEDbigint(20)NONULLCurrently allocated blocks that have not been freed (COUNT_ALLOC minus COUNT_FREE).
HIGH_COUNT_USEDbigint(20)NONULLHighest number of allocated blocks (highest value of CURRENT_COUNT_USED).
LOW_NUMBER_OF_BYTES_USEDbigint(20)NONULLLowest number of bytes used.
CURRENT_NUMBER_OF_BYTES_USEDbigint(20)NONULLCurrent number of bytes used (total allocated minus total freed).
HIGH_NUMBER_OF_BYTES_USEDbigint(20)NONULLHighest number of bytes used.

1.1.1.2.9.2.1.45 Performance Schema memory_summary_by_user_by_event_name Table

MariaDB starting with 10.5.2

The memory_summary_by_user_by_event_name table was introduced in MariaDB 10.5.2.

There are five memory summary tables in the Performance Schema that share a number of fields in common. These include:

The memory_summary_by_user_by_event_name table contains memory usage statistics aggregated by user and event.

The table contains the following columns:

FieldTypeNullDefaultDescription
USERchar(32)YESNULLUser portion of the account.
EVENT_NAMEvarchar(128)NONULLEvent name.
COUNT_ALLOCbigint(20) unsignedNONULLTotal number of allocations to memory.
COUNT_FREEbigint(20) unsignedNONULLTotal number of attempts to free the allocated memory.
SUM_NUMBER_OF_BYTES_ALLOCbigint(20) unsignedNONULLTotal number of bytes allocated.
SUM_NUMBER_OF_BYTES_FREEbigint(20) unsignedNONULLTotal number of bytes freed
LOW_COUNT_USEDbigint(20)NONULLLowest number of allocated blocks (lowest value of CURRENT_COUNT_USED).
CURRENT_COUNT_USEDbigint(20)NONULLCurrently allocated blocks that have not been freed (COUNT_ALLOC minus COUNT_FREE).
HIGH_COUNT_USEDbigint(20)NONULLHighest number of allocated blocks (highest value of CURRENT_COUNT_USED).
LOW_NUMBER_OF_BYTES_USEDbigint(20)NONULLLowest number of bytes used.
CURRENT_NUMBER_OF_BYTES_USEDbigint(20)NONULLCurrent number of bytes used (total allocated minus total freed).
HIGH_NUMBER_OF_BYTES_USEDbigint(20)NONULLHighest number of bytes used.

1.1.1.2.9.2.1.46 Performance Schema memory_summary_global_by_event_name Table

MariaDB starting with 10.5.2

The memory_summary_global_by_event_name table was introduced in MariaDB 10.5.2.

There are five memory summary tables in the Performance Schema that share a number of fields in common. These include:

The memory_summary_global_by_event_name table contains memory usage statistics aggregated by event and event.

The table contains the following columns:

FieldTypeNullDefaultDescription
EVENT_NAMEvarchar(128)NONULLEvent name.
COUNT_ALLOCbigint(20) unsignedNONULLTotal number of allocations to memory.
COUNT_FREEbigint(20) unsignedNONULLTotal number of attempts to free the allocated memory.
SUM_NUMBER_OF_BYTES_ALLOCbigint(20) unsignedNONULLTotal number of bytes allocated.
SUM_NUMBER_OF_BYTES_FREEbigint(20) unsignedNONULLTotal number of bytes freed
LOW_COUNT_USEDbigint(20)NONULLLowest number of allocated blocks (lowest value of CURRENT_COUNT_USED).
CURRENT_COUNT_USEDbigint(20)NONULLCurrently allocated blocks that have not been freed (COUNT_ALLOC minus COUNT_FREE).
HIGH_COUNT_USEDbigint(20)NONULLHighest number of allocated blocks (highest value of CURRENT_COUNT_USED).
LOW_NUMBER_OF_BYTES_USEDbigint(20)NONULLLowest number of bytes used.
CURRENT_NUMBER_OF_BYTES_USEDbigint(20)NONULLCurrent number of bytes used (total allocated minus total freed).
HIGH_NUMBER_OF_BYTES_USEDbigint(20)NONULLHighest number of bytes used.

Example

Seeing what memory was most often allocated for:

SELECT * FROM memory_summary_global_by_event_name 
  ORDER BY count_alloc DESC LIMIT 1\G
*************************** 1. row ***************************
                  EVENT_NAME: memory/sql/QUICK_RANGE_SELECT::alloc
                 COUNT_ALLOC: 147976
                  COUNT_FREE: 147976
   SUM_NUMBER_OF_BYTES_ALLOC: 600190656
    SUM_NUMBER_OF_BYTES_FREE: 600190656
              LOW_COUNT_USED: 0
          CURRENT_COUNT_USED: 0
             HIGH_COUNT_USED: 68
    LOW_NUMBER_OF_BYTES_USED: 0
CURRENT_NUMBER_OF_BYTES_USED: 0
   HIGH_NUMBER_OF_BYTES_USED: 275808

1.1.1.2.9.2.1.47 Performance Schema metadata_locks Table

MariaDB starting with 10.5.2

The metadata_locks table was introduced in MariaDB 10.5.2.

The metadata_locks table contains metadata lock information.

To enable metadata lock instrumention, at runtime:

UPDATE performance_schema.setup_instruments SET enabled='YES', timed='YES' 
  WHERE name LIKE 'wait/lock/metadata%';

or in the configuration file:

performance-schema-instrument='wait/lock/metadata/sql/mdl=ON'

The table is by default autosized, but the size can be configured with the performance_schema_max_metadata_locks system variabe.

The table is read-only, and TRUNCATE TABLE cannot be used to empty the table.

The table contains the following columns:

FieldTypeNullDefaultDescription
OBJECT_TYPEvarchar(64)NONULLObject type. One of BACKUP, COMMIT, EVENT, FUNCTION, GLOBAL, LOCKING SERVICE, PROCEDURE, SCHEMA, TABLE, TABLESPACE, TRIGGER (unused) or USER LEVEL LOCK.
OBJECT_SCHEMAvarchar(64)YESNULLObject schema.
OBJECT_NAMEvarchar(64)YESNULLObject name.
OBJECT_INSTANCE_BEGINbigint(20) unsignedNONULLAddress in memory of the instrumented object.
LOCK_TYPEvarchar(32)NONULLLock type. One of BACKUP_FTWRL1, BACKUP_START, BACKUP_TRANS_DML, EXCLUSIVE, INTENTION_EXCLUSIVE, SHARED, SHARED_HIGH_PRIO, SHARED_NO_READ_WRITE, SHARED_NO_WRITE, SHARED_READ, SHARED_UPGRADABLE or SHARED_WRITE.
LOCK_DURATIONvarchar(32)NONULLLock duration. One of EXPLICIT (locks released by explicit action, for example a global lock acquired with FLUSH TABLES WITH READ LOCK) , STATEMENT (locks implicitly released at statement end) or TRANSACTION (locks implicitly released at transaction end).
LOCK_STATUSvarchar(32)NONULLLock status. One of GRANTED, KILLED, PENDING, POST_RELEASE_NOTIFY, PRE_ACQUIRE_NOTIFY, TIMEOUT or VICTIM.
SOURCEvarchar(64)YESNULLSource file containing the instrumented code that produced the event, as well as the line number where the instrumentation occurred. This allows one to examine the source code involved.
OWNER_THREAD_IDbigint(20) unsignedYESNULLThread that requested the lock.
OWNER_EVENT_IDbigint(20) unsignedYESNULLEvent that requested the lock.

1.1.1.2.9.2.1.48 Performance Schema mutex_instances Table

Description

The mutex_instances table lists all mutexes that the Performance Schema seeing while the server is executing.

A mutex is a code mechanism for ensuring that threads can only access resources one at a time. A second thread attempting to access a resource will find it protected by a mutex, and will wait for it to be unlocked.

The performance_schema_max_mutex_instances system variable specifies the maximum number of instrumented mutex instances.

ColumnDescription
NAMEInstrument name associated with the mutex.
OBJECT_INSTANCE_BEGINMemory address of the instrumented mutex.
LOCKED_BY_THREAD_IDThe THREAD_ID of the locking thread if a thread has a mutex locked, otherwise NULL.

1.1.1.2.9.2.1.49 Performance Schema objects_summary_global_by_type Table

It aggregates object wait events, and contains the following columns:

ColumnDescription
OBJECT_TYPEGroups records together with OBJECT_SCHEMA and OBJECT_NAME.
OBJECT_SCHEMAGroups records together with OBJECT_TYPE and OBJECT_NAME.
OBJECT_NAMEGroups records together with OBJECT_SCHEMA and OBJECT_TYPE.
COUNT_STARNumber of summarized events
SUM_TIMER_WAITTotal wait time of the summarized events that are timed.
MIN_TIMER_WAITMinimum wait time of the summarized events that are timed.
AVG_TIMER_WAITAverage wait time of the summarized events that are timed.
MAX_TIMER_WAITMaximum wait time of the summarized events that are timed.

You can TRUNCATE the table, which will reset all counters to zero.

Example

SELECT * FROM objects_summary_global_by_type\G
...
*************************** 101. row ***************************
   OBJECT_TYPE: TABLE
 OBJECT_SCHEMA: test
   OBJECT_NAME: v
    COUNT_STAR: 0
SUM_TIMER_WAIT: 0
MIN_TIMER_WAIT: 0
AVG_TIMER_WAIT: 0
MAX_TIMER_WAIT: 0
*************************** 102. row ***************************
   OBJECT_TYPE: TABLE
 OBJECT_SCHEMA: test
   OBJECT_NAME: xx2
    COUNT_STAR: 2
SUM_TIMER_WAIT: 1621920
MIN_TIMER_WAIT: 481344
AVG_TIMER_WAIT: 810960
MAX_TIMER_WAIT: 1140576

1.1.1.2.9.2.1.50 Performance Schema performance_timers Table

Description

The performance_timers table lists available event timers.

It contains the following columns:

ColumnDescription
TIMER_NAMETime name, used in the setup_timers table.
TIMER_FREQUENCYNumber of timer units per second. Dependent on the processor speed.
TIMER_RESOLUTIONNumber of timer units by which timed values increase each time.
TIMER_OVERHEADMinimum timer overhead, determined during initialization by calling the timer 20 times and selecting the smallest value. Total overhead will be at least double this, as the timer is called at the beginning and end of each timed event.

Any NULL values indicate that that particular timer is not available on your platform, Any timer names with a non-NULL value can be used in the setup_timers table.

Example

SELECT * FROM performance_timers;
+-------------+-----------------+------------------+---------------------+
| TIMER_NAME  | TIMER_FREQUENCY | TIMER_RESOLUTION | TIMER_OVERHEAD      |
+-------------+-----------------+------------------+---------------------+
| CYCLE       |      2293651741 |                1 |                  28 |
| NANOSECOND  |      1000000000 |                1 |                  48 |
| MICROSECOND |         1000000 |                1 |                  52 |
| MILLISECOND |            1000 |             1000 | 9223372036854775807 |
| TICK        |             106 |                1 |                 496 |
+-------------+-----------------+------------------+---------------------+

1.1.1.2.9.2.1.51 Performance Schema prepared_statements_instances Table

MariaDB starting with 10.5.2

The prepared_statements_instances table was introduced in MariaDB 10.5.2.

The prepared_statements_instances table contains aggregated statistics of prepared statements.

The maximum number of rows in the table is determined by the performance_schema_max_prepared_statement_instances system variable, which is by default autosized on startup.

The table contains the following columns:

+-----------------------------+--------------------------------------------------------+------+-----+---------+-------+
| Field                       | Type                                                   | Null | Key | Default | Extra |
+-----------------------------+--------------------------------------------------------+------+-----+---------+-------+
| OBJECT_INSTANCE_BEGIN       | bigint(20) unsigned                                    | NO   |     | NULL    |       |
| STATEMENT_ID                | bigint(20) unsigned                                    | NO   |     | NULL    |       |
| STATEMENT_NAME              | varchar(64)                                            | YES  |     | NULL    |       |
| SQL_TEXT                    | longtext                                               | NO   |     | NULL    |       |
| OWNER_THREAD_ID             | bigint(20) unsigned                                    | NO   |     | NULL    |       |
| OWNER_EVENT_ID              | bigint(20) unsigned                                    | NO   |     | NULL    |       |
| OWNER_OBJECT_TYPE           | enum('EVENT','FUNCTION','PROCEDURE','TABLE','TRIGGER') | YES  |     | NULL    |       |
| OWNER_OBJECT_SCHEMA         | varchar(64)                                            | YES  |     | NULL    |       |
| OWNER_OBJECT_NAME           | varchar(64)                                            | YES  |     | NULL    |       |
| TIMER_PREPARE               | bigint(20) unsigned                                    | NO   |     | NULL    |       |
| COUNT_REPREPARE             | bigint(20) unsigned                                    | NO   |     | NULL    |       |
| COUNT_EXECUTE               | bigint(20) unsigned                                    | NO   |     | NULL    |       |
| SUM_TIMER_EXECUTE           | bigint(20) unsigned                                    | NO   |     | NULL    |       |
| MIN_TIMER_EXECUTE           | bigint(20) unsigned                                    | NO   |     | NULL    |       |
| AVG_TIMER_EXECUTE           | bigint(20) unsigned                                    | NO   |     | NULL    |       |
| MAX_TIMER_EXECUTE           | bigint(20) unsigned                                    | NO   |     | NULL    |       |
| SUM_LOCK_TIME               | bigint(20) unsigned                                    | NO   |     | NULL    |       |
| SUM_ERRORS                  | bigint(20) unsigned                                    | NO   |     | NULL    |       |
| SUM_WARNINGS                | bigint(20) unsigned                                    | NO   |     | NULL    |       |
| SUM_ROWS_AFFECTED           | bigint(20) unsigned                                    | NO   |     | NULL    |       |
| SUM_ROWS_SENT               | bigint(20) unsigned                                    | NO   |     | NULL    |       |
| SUM_ROWS_EXAMINED           | bigint(20) unsigned                                    | NO   |     | NULL    |       |
| SUM_CREATED_TMP_DISK_TABLES | bigint(20) unsigned                                    | NO   |     | NULL    |       |
| SUM_CREATED_TMP_TABLES      | bigint(20) unsigned                                    | NO   |     | NULL    |       |
| SUM_SELECT_FULL_JOIN        | bigint(20) unsigned                                    | NO   |     | NULL    |       |
| SUM_SELECT_FULL_RANGE_JOIN  | bigint(20) unsigned                                    | NO   |     | NULL    |       |
| SUM_SELECT_RANGE            | bigint(20) unsigned                                    | NO   |     | NULL    |       |
| SUM_SELECT_RANGE_CHECK      | bigint(20) unsigned                                    | NO   |     | NULL    |       |
| SUM_SELECT_SCAN             | bigint(20) unsigned                                    | NO   |     | NULL    |       |
| SUM_SORT_MERGE_PASSES       | bigint(20) unsigned                                    | NO   |     | NULL    |       |
| SUM_SORT_RANGE              | bigint(20) unsigned                                    | NO   |     | NULL    |       |
| SUM_SORT_ROWS               | bigint(20) unsigned                                    | NO   |     | NULL    |       |
| SUM_SORT_SCAN               | bigint(20) unsigned                                    | NO   |     | NULL    |       |
| SUM_NO_INDEX_USED           | bigint(20) unsigned                                    | NO   |     | NULL    |       |
| SUM_NO_GOOD_INDEX_USED      | bigint(20) unsigned                                    | NO   |     | NULL    |       |
+-----------------------------+--------------------------------------------------------+------+-----+---------+-------+

1.1.1.2.9.2.1.52 Performance Schema replication_applier_configuration Table

MariaDB starting with 10.5.2

The replication_applier_configuration table, along with many other new Performance Schema tables, was added in MariaDB 10.5.2.

The Performance Schema replication_applier_configuration table contains configuration settings affecting replica transactions.

It contains the following fields.

FieldTypeNullDescription
CHANNEL_NAMEchar(64)NOReplication channel name.
DESIRED_DELAYint(11)NOTarget number of seconds the replica should be delayed to the master.

1.1.1.2.9.2.1.53 Performance Schema replication_applier_status Table

MariaDB starting with 10.5.2

The replication_applier_status table, along with many other new Performance Schema tables, was added in MariaDB 10.5.2.

The Performance Schema replication_applier_status table contains information about the general transaction execution status on the replica.

It contains the following fields.

FieldTypeNullDescription
CHANNEL_NAMEchar(64)NOThe replication channel name.
SERVICE_STATEenum('ON','OFF')NOShows ON when the replication channel's applier threads are active or idle, OFF means that the applier threads are not active.
REMAINING_DELAYint(10) unsignedYESSeconds the replica needs to wait to reach the desired delay from master.
COUNT_TRANSACTIONS_RETRIESbigint(20) unsignedNOThe number of retries that were made because the replication SQL thread failed to apply a transaction.

1.1.1.2.9.2.1.54 Performance Schema replication_applier_status_by_coordinator Table

MariaDB starting with 10.5.2

The replication_applier_status_by_coordinator table was added in MariaDB 10.5.2.

The Performance Schema replication_applier_status_by_coordinator table displays the status of the coordinator thread used in multi-threaded replicas to manage multiple worker threads.

It contains the following fields.

ColumnTypeNullDescription
CHANNEL_NAMEvarchar(256)NOReplication channel name.
THREAD_IDbigint(20) unsignedYESThe SQL/coordinator thread ID.
SERVICE_STATEenum('ON','OFF')NOON (thread exists and is active or idle) or OFF (thread no longer exists).
LAST_ERROR_NUMBERint(11)NOLast error number that caused the SQL/coordinator thread to stop.
LAST_ERROR_MESSAGEvarchar(1024)NOLast error message that caused the SQL/coordinator thread to stop.
LAST_ERROR_TIMESTAMPtimestampNOTimestamp that shows when the most recent SQL/coordinator error occured.
LAST_SEEN_TRANSACTIONchar(57)NOThe transaction the worker has last seen.
LAST_TRANS_RETRY_COUNTint(11)NOTotal number of retries attempted by last transaction.

1.1.1.2.9.2.1.55 Performance Schema replication_applier_status_by_worker Table

MariaDB starting with 10.6.0

The replication_applier_status_by_worker table was added in MariaDB 10.6.0.

The Performance Schema replication_applier_status_by_worker table displays replica worker thread specific information.

It contains the following fields.

ColumnDescription
CHANNEL_NAMEName of replication channel through which the transaction is received.
THREAD_IDThread_Id as displayed in the performance_schema.threads table for thread with name 'thread/sql/rpl_parallel_thread'. THREAD_ID will be NULL when worker threads are stopped due to error/force stop.
SERVICE_STATEWhether or not the thread is running.
LAST_SEEN_TRANSACTIONLast GTID executed by worker
LAST_ERROR_NUMBERLast Error that occurred on a particular worker.
LAST_ERROR_MESSAGELast error specific message.
LAST_ERROR_TIMESTAMPTime stamp of last error.
WORKER_IDLE_TIMETotal idle time in seconds that the worker thread has spent waiting for work from SQL thread.
LAST_TRANS_RETRY_COUNTTotal number of retries attempted by last transaction.

1.1.1.2.9.2.1.56 Performance Schema replication_connection_configuration Table

MariaDB starting with 10.5.2

The replication_connection_configuration table was added in MariaDB 10.6.0.

The Performance Schema replication_connection_configuration table displays replica's configuration settings used for connecting to the primary.

It contains the following fields.

ColumnTypeNullDescription
CHANNEL_NAMEvarchar(256)NOThe replication channel used.
HOSTchar(60)NOThe host name of the source that the replica is connected to.
PORTint(11)NOThe port used to connect to the source.
USERchar(32)NOThe user name of the replication user account used to connect to the source.
USING_GTIDenum('NO', 'CURRENT_POS', 'SLAVE_POS')NOWhether replication is using GTIDs or not.
SSL_ALLOWEDenum('YES', 'NO', 'IGNORED')NOWhether SSL is allowed for the replica connection.
SSL_CA_FILEvarchar(512)NOPath to the file that contains one or more certificates for trusted Certificate Authorities (CA) to use for TLS.
SSL_CA_PATHvarchar(512)NOPath to a directory that contains one or more PEM files that contain X509 certificates for a trusted Certificate Authority (CA) to use for TLS.
SSL_CERTIFICATEvarchar(512)NOPath to the certificate used to authenticate the master.
SSL_CIPHERvarchar(512)NOWhich cipher is used for encription.
SSL_KEYvarchar(512)NOPath to the private key used for TLS.
SSL_VERIFY_SERVER_CERTIFICATEenum('YES','NO')NOWhether the server certificate is verified as part of the SSL connection.
SSL_CRL_FILEvarchar(255)NOPath to the PEM file containing one or more revoked X.509 certificates.
SSL_CRL_PATHvarchar(255)NOPATH to a folder containing PEM files containing one or more revoked X.509 certificates.
CONNECTION_RETRY_INTERVALint(11)NOThe number of seconds between connect retries.
CONNECTION_RETRY_COUNTbigint(20) unsignedNOThe number of times the replica can attempt to reconnect to the source in the event of a lost connection.
HEARTBEAT_INTERVALdouble(10,3) unsignedNONumber of seconds after which a heartbeat will be sent.
IGNORE_SERVER_IDSlongtextNOBinary log events from servers (ids) to ignore.
REPL_DO_DOMAIN_IDSlongtextNOOnly apply binary logs from these domain ids.
REPL_IGNORE_DOMAIN_IDSlongtextNOBinary log events from domains to ignore.

1.1.1.2.9.2.1.57 Performance Schema rwlock_instances Table

The rwlock_instances table lists all read write lock (rwlock) instances that the Performance Schema sees while the server is executing. A read write is a mechanism for ensuring threads can either share access to common resources, or have exclusive access.

The performance_schema_max_rwlock_instances system variable specifies the maximum number of instrumented rwlock objects.

The rwlock_instances table contains the following columns:

ColumnDescription
NAMEInstrument name associated with the read write lock
OBJECT_INSTANCE_BEGINAddress in memory of the instrumented lock
WRITE_LOCKED_BY_THREAD_IDTHREAD_ID of the locking thread if locked in write (exclusive) mode, otherwise NULL.
READ_LOCKED_BY_COUNTCount of current read locks held

1.1.1.2.9.2.1.58 Performance Schema session_account_connect_attrs Table

Description

The session_account_connect_attrs table shows connection attributes for the current session.

Applications can pass key/value connection attributes to the server when a connection is made. The session_connect_attrs and session_account_connect_attrs tables provide access to this information, for all sessions and the current session respectively.

The C API functions mysql_options() and mysql_optionsv() are used for passing connection attributes to the server.

session_account_connect_attrs contains the following columns:

ColumnDescription
PROCESSLIST_IDSession connection identifier.
ATTR_NAMEAttribute name.
ATTR_VALUEAttribute value.
ORDINAL_POSITIONOrder in which attribute was added to the connection attributes.

Example

SELECT * FROM performance_schema.session_account_connect_attrs;
+----------------+-----------------+------------------+------------------+
| PROCESSLIST_ID | ATTR_NAME       | ATTR_VALUE       | ORDINAL_POSITION |
+----------------+-----------------+------------------+------------------+
|             45 | _os             | debian-linux-gnu |                0 |
|             45 | _client_name    | libmysql         |                1 |
|             45 | _pid            | 7711             |                2 |
|             45 | _client_version | 10.0.5           |                3 |
|             45 | _platform       | x86_64           |                4 |
|             45 | program_name    | mysql            |                5 |
+----------------+-----------------+------------------+------------------+

1.1.1.2.9.2.1.59 Performance Schema session_connect_attrs Table

Description

The session_connect_attrs table shows connection attributes for all sessions.

Applications can pass key/value connection attributes to the server when a connection is made. The session_connect_attrs and session_account_connect_attrs tables provide access to this information, for all sessions and the current session respectively.

The C API functions mysql_options() and mysql_optionsv() are used for passing connection attributes to the server.

session_connect_attrs contains the following columns:

ColumnDescription
PROCESSLIST_IDSession connection identifier.
ATTR_NAMEAttribute name.
ATTR_VALUEAttribute value.
ORDINAL_POSITIONOrder in which attribute was added to the connection attributes.

Example

Returning the current connection's attributes:

SELECT * FROM performance_schema.session_connect_attrs WHERE processlist_id=CONNECTION_ID();
+----------------+-----------------+------------------+------------------+
| PROCESSLIST_ID | ATTR_NAME       | ATTR_VALUE       | ORDINAL_POSITION |
+----------------+-----------------+------------------+------------------+
|             45 | _os             | debian-linux-gnu |                0 |
|             45 | _client_name    | libmysql         |                1 |
|             45 | _pid            | 7711             |                2 |
|             45 | _client_version | 10.0.5           |                3 |
|             45 | _platform       | x86_64           |                4 |
|             45 | program_name    | mysql            |                5 |
+----------------+-----------------+------------------+------------------+

1.1.1.2.9.2.1.60 Performance Schema session_status Table

MariaDB starting with 10.5.2

The session_status table was added in MariaDB 10.5.2.

The session_status table contains a list of status variables for the current session. The table only stores status variable statistics for threads which are instrumented, and does not collect statistics for Com_xxx variables.

The table contains the following columns:

ColumnDescription
VARIABLE_NAMEThe session status variable name.
VARIABLE_VALUEThe session status variable value.

It is not possible to empty this table with a TRUNCATE TABLE statement.

1.1.1.2.9.2.1.61 Performance Schema setup_actors Table

The setup_actors table contains information for determining whether monitoring should be enabled for new client connection threads.

The default size is 100 rows, which can be changed by modifying the performance_schema_setup_actors_size system variable at server startup.

If a row in the table matches a new foreground thread's client and host, the matching INSTRUMENTED column in the threads table is set to either YES or NO, which allows selective application of instrumenting by host, by user, or combination thereof.

ColumnDescription
HOSTHost name, either a literal, or the % wildcard representing any host.
USERUser name, either a literal or the % wildcard representing any name.
ROLEUnused

Initially, any user and host is matched:

SELECT * FROM performance_schema.setup_actors;
+------+------+------+
| HOST | USER | ROLE |
+------+------+------+
| %    | %    | %    |
+------+------+------+

1.1.1.2.9.2.1.62 Performance Schema setup_consumers Table

Lists the types of consumers for which event information is available.

The setup_consumers table contains the following columns:

ColumnDescription
NAMEConsumer name
ENABLEDYES or NO for whether or not the consumer is enabled. You can modify this column to ensure that event information is added, or is not added.

The table can be modified directly, or the server started with the option enabled, for example:

performance-schema-consumer-events-waits-history=ON

Example

SELECT * FROM performance_schema.setup_consumers;

+--------------------------------+---------+
| NAME                           | ENABLED |
+--------------------------------+---------+
| events_stages_current          | NO      |
| events_stages_history          | NO      |
| events_stages_history_long     | NO      |
| events_statements_current      | YES     |
| events_statements_history      | NO      |
| events_statements_history_long | NO      |
| events_waits_current           | NO      |
| events_waits_history           | NO      |
| events_waits_history_long      | NO      |
| global_instrumentation         | YES     |
| thread_instrumentation         | YES     |
| statements_digest              | YES     |
+--------------------------------+---------+

See Also

1.1.1.2.9.2.1.63 Performance Schema setup_instruments Table

The setup_instruments table contains a list of instrumented object classes for which it is possible to collect events. There is one row for each instrument in the source code. When an instrument is enabled and executed, instances are created which are then stored in the cond_instances, file_instances, mutex_instances, rwlock_instances or socket_instance tables.

It contains the following columns:

ColumnDescription
NAMEInstrument name
ENABLEDWhether or not the instrument is enabled. It can be disabled, and the instrument will produce no events.
TIMEDWhether or not the instrument is timed. It can be set, but if disabled, events produced by the instrument will have NULL values for the corresponding TIMER_START, TIMER_END, and TIMER_WAIT values.

Example

From MariaDB 10.5.7, default settings with the Performance Schema enabled:

SELECT * FROM setup_instruments ORDER BY name;
+--------------------------------------------------------------------------------+---------+-------+
| NAME                                                                           | ENABLED | TIMED |
+--------------------------------------------------------------------------------+---------+-------+
| idle                                                                           | YES     | YES   |
| memory/csv/blobroot                                                            | NO      | NO    |
| memory/csv/row                                                                 | NO      | NO    |
| memory/csv/tina_set                                                            | NO      | NO    |
| memory/csv/TINA_SHARE                                                          | NO      | NO    |
| memory/csv/Transparent_file                                                    | NO      | NO    |
| memory/innodb/adaptive hash index                                              | NO      | NO    |
| memory/innodb/btr0btr                                                          | NO      | NO    |
| memory/innodb/btr0buf                                                          | NO      | NO    |
| memory/innodb/btr0bulk                                                         | NO      | NO    |
| memory/innodb/btr0cur                                                          | NO      | NO    |
| memory/innodb/btr0pcur                                                         | NO      | NO    |
| memory/innodb/btr0sea                                                          | NO      | NO    |
| memory/innodb/buf0buf                                                          | NO      | NO    |
| memory/innodb/buf0dblwr                                                        | NO      | NO    |
| memory/innodb/buf0dump                                                         | NO      | NO    |
| memory/innodb/buf_buf_pool                                                     | NO      | NO    |
| memory/innodb/dict0dict                                                        | NO      | NO    |
| memory/innodb/dict0mem                                                         | NO      | NO    |
| memory/innodb/dict0stats                                                       | NO      | NO    |
| memory/innodb/dict_stats_bg_recalc_pool_t                                      | NO      | NO    |
| memory/innodb/dict_stats_index_map_t                                           | NO      | NO    |
| memory/innodb/dict_stats_n_diff_on_level                                       | NO      | NO    |
| memory/innodb/eval0eval                                                        | NO      | NO    |
| memory/innodb/fil0crypt                                                        | NO      | NO    |
| memory/innodb/fil0fil                                                          | NO      | NO    |
| memory/innodb/fsp0file                                                         | NO      | NO    |
| memory/innodb/fts0ast                                                          | NO      | NO    |
| memory/innodb/fts0blex                                                         | NO      | NO    |
| memory/innodb/fts0config                                                       | NO      | NO    |
| memory/innodb/fts0file                                                         | NO      | NO    |
| memory/innodb/fts0fts                                                          | NO      | NO    |
| memory/innodb/fts0opt                                                          | NO      | NO    |
| memory/innodb/fts0pars                                                         | NO      | NO    |
| memory/innodb/fts0que                                                          | NO      | NO    |
| memory/innodb/fts0sql                                                          | NO      | NO    |
| memory/innodb/fts0tlex                                                         | NO      | NO    |
| memory/innodb/gis0sea                                                          | NO      | NO    |
| memory/innodb/handler0alter                                                    | NO      | NO    |
| memory/innodb/hash0hash                                                        | NO      | NO    |
| memory/innodb/ha_innodb                                                        | NO      | NO    |
| memory/innodb/i_s                                                              | NO      | NO    |
| memory/innodb/lexyy                                                            | NO      | NO    |
| memory/innodb/lock0lock                                                        | NO      | NO    |
| memory/innodb/mem0mem                                                          | NO      | NO    |
| memory/innodb/os0event                                                         | NO      | NO    |
| memory/innodb/os0file                                                          | NO      | NO    |
| memory/innodb/other                                                            | NO      | NO    |
| memory/innodb/pars0lex                                                         | NO      | NO    |
| memory/innodb/rem0rec                                                          | NO      | NO    |
| memory/innodb/row0ftsort                                                       | NO      | NO    |
| memory/innodb/row0import                                                       | NO      | NO    |
| memory/innodb/row0log                                                          | NO      | NO    |
| memory/innodb/row0merge                                                        | NO      | NO    |
| memory/innodb/row0mysql                                                        | NO      | NO    |
| memory/innodb/row0sel                                                          | NO      | NO    |
| memory/innodb/row_log_buf                                                      | NO      | NO    |
| memory/innodb/row_merge_sort                                                   | NO      | NO    |
| memory/innodb/srv0start                                                        | NO      | NO    |
| memory/innodb/std                                                              | NO      | NO    |
| memory/innodb/sync0arr                                                         | NO      | NO    |
| memory/innodb/sync0debug                                                       | NO      | NO    |
| memory/innodb/sync0rw                                                          | NO      | NO    |
| memory/innodb/sync0start                                                       | NO      | NO    |
| memory/innodb/sync0types                                                       | NO      | NO    |
| memory/innodb/trx0i_s                                                          | NO      | NO    |
| memory/innodb/trx0roll                                                         | NO      | NO    |
| memory/innodb/trx0rseg                                                         | NO      | NO    |
| memory/innodb/trx0seg                                                          | NO      | NO    |
| memory/innodb/trx0trx                                                          | NO      | NO    |
| memory/innodb/trx0undo                                                         | NO      | NO    |
| memory/innodb/ut0list                                                          | NO      | NO    |
| memory/innodb/ut0mem                                                           | NO      | NO    |
| memory/innodb/ut0new                                                           | NO      | NO    |
| memory/innodb/ut0pool                                                          | NO      | NO    |
| memory/innodb/ut0rbt                                                           | NO      | NO    |
| memory/innodb/ut0wqueue                                                        | NO      | NO    |
| memory/innodb/xtrabackup                                                       | NO      | NO    |
| memory/memory/HP_INFO                                                          | NO      | NO    |
| memory/memory/HP_KEYDEF                                                        | NO      | NO    |
| memory/memory/HP_PTRS                                                          | NO      | NO    |
| memory/memory/HP_SHARE                                                         | NO      | NO    |
| memory/myisam/filecopy                                                         | NO      | NO    |
| memory/myisam/FTB                                                              | NO      | NO    |
| memory/myisam/FTPARSER_PARAM                                                   | NO      | NO    |
| memory/myisam/FT_INFO                                                          | NO      | NO    |
| memory/myisam/ft_memroot                                                       | NO      | NO    |
| memory/myisam/ft_stopwords                                                     | NO      | NO    |
| memory/myisam/keycache_thread_var                                              | NO      | NO    |
| memory/myisam/MI_DECODE_TREE                                                   | NO      | NO    |
| memory/myisam/MI_INFO                                                          | NO      | NO    |
| memory/myisam/MI_INFO::bulk_insert                                             | NO      | NO    |
| memory/myisam/MI_INFO::ft1_to_ft2                                              | NO      | NO    |
| memory/myisam/MI_SORT_PARAM                                                    | NO      | NO    |
| memory/myisam/MI_SORT_PARAM::wordroot                                          | NO      | NO    |
| memory/myisam/MYISAM_SHARE                                                     | NO      | NO    |
| memory/myisam/MYISAM_SHARE::decode_tables                                      | NO      | NO    |
| memory/myisam/preload_buffer                                                   | NO      | NO    |
| memory/myisam/record_buffer                                                    | NO      | NO    |
| memory/myisam/SORT_FT_BUF                                                      | NO      | NO    |
| memory/myisam/SORT_INFO::buffer                                                | NO      | NO    |
| memory/myisam/SORT_KEY_BLOCKS                                                  | NO      | NO    |
| memory/myisam/stPageList::pages                                                | NO      | NO    |
| memory/myisammrg/children                                                      | NO      | NO    |
| memory/myisammrg/MYRG_INFO                                                     | NO      | NO    |
| memory/partition/ha_partition::file                                            | NO      | NO    |
| memory/partition/ha_partition::part_ids                                        | NO      | NO    |
| memory/partition/Partition_admin                                               | NO      | NO    |
| memory/partition/Partition_share                                               | NO      | NO    |
| memory/partition/partition_sort_buffer                                         | NO      | NO    |
| memory/performance_schema/accounts                                             | YES     | NO    |
| memory/performance_schema/cond_class                                           | YES     | NO    |
| memory/performance_schema/cond_instances                                       | YES     | NO    |
| memory/performance_schema/events_stages_history                                | YES     | NO    |
| memory/performance_schema/events_stages_history_long                           | YES     | NO    |
| memory/performance_schema/events_stages_summary_by_account_by_event_name       | YES     | NO    |
| memory/performance_schema/events_stages_summary_by_host_by_event_name          | YES     | NO    |
| memory/performance_schema/events_stages_summary_by_thread_by_event_name        | YES     | NO    |
| memory/performance_schema/events_stages_summary_by_user_by_event_name          | YES     | NO    |
| memory/performance_schema/events_stages_summary_global_by_event_name           | YES     | NO    |
| memory/performance_schema/events_statements_current                            | YES     | NO    |
| memory/performance_schema/events_statements_current.sqltext                    | YES     | NO    |
| memory/performance_schema/events_statements_current.tokens                     | YES     | NO    |
| memory/performance_schema/events_statements_history                            | YES     | NO    |
| memory/performance_schema/events_statements_history.sqltext                    | YES     | NO    |
| memory/performance_schema/events_statements_history.tokens                     | YES     | NO    |
| memory/performance_schema/events_statements_history_long                       | YES     | NO    |
| memory/performance_schema/events_statements_history_long.sqltext               | YES     | NO    |
| memory/performance_schema/events_statements_history_long.tokens                | YES     | NO    |
| memory/performance_schema/events_statements_summary_by_account_by_event_name   | YES     | NO    |
| memory/performance_schema/events_statements_summary_by_digest                  | YES     | NO    |
| memory/performance_schema/events_statements_summary_by_digest.tokens           | YES     | NO    |
| memory/performance_schema/events_statements_summary_by_host_by_event_name      | YES     | NO    |
| memory/performance_schema/events_statements_summary_by_program                 | YES     | NO    |
| memory/performance_schema/events_statements_summary_by_thread_by_event_name    | YES     | NO    |
| memory/performance_schema/events_statements_summary_by_user_by_event_name      | YES     | NO    |
| memory/performance_schema/events_statements_summary_global_by_event_name       | YES     | NO    |
| memory/performance_schema/events_transactions_history                          | YES     | NO    |
| memory/performance_schema/events_transactions_history_long                     | YES     | NO    |
| memory/performance_schema/events_transactions_summary_by_account_by_event_name | YES     | NO    |
| memory/performance_schema/events_transactions_summary_by_host_by_event_name    | YES     | NO    |
| memory/performance_schema/events_transactions_summary_by_thread_by_event_name  | YES     | NO    |
| memory/performance_schema/events_transactions_summary_by_user_by_event_name    | YES     | NO    |
| memory/performance_schema/events_waits_history                                 | YES     | NO    |
| memory/performance_schema/events_waits_history_long                            | YES     | NO    |
| memory/performance_schema/events_waits_summary_by_account_by_event_name        | YES     | NO    |
| memory/performance_schema/events_waits_summary_by_host_by_event_name           | YES     | NO    |
| memory/performance_schema/events_waits_summary_by_thread_by_event_name         | YES     | NO    |
| memory/performance_schema/events_waits_summary_by_user_by_event_name           | YES     | NO    |
| memory/performance_schema/file_class                                           | YES     | NO    |
| memory/performance_schema/file_handle                                          | YES     | NO    |
| memory/performance_schema/file_instances                                       | YES     | NO    |
| memory/performance_schema/hosts                                                | YES     | NO    |
| memory/performance_schema/memory_class                                         | YES     | NO    |
| memory/performance_schema/memory_summary_by_account_by_event_name              | YES     | NO    |
| memory/performance_schema/memory_summary_by_host_by_event_name                 | YES     | NO    |
| memory/performance_schema/memory_summary_by_thread_by_event_name               | YES     | NO    |
| memory/performance_schema/memory_summary_by_user_by_event_name                 | YES     | NO    |
| memory/performance_schema/memory_summary_global_by_event_name                  | YES     | NO    |
| memory/performance_schema/metadata_locks                                       | YES     | NO    |
| memory/performance_schema/mutex_class                                          | YES     | NO    |
| memory/performance_schema/mutex_instances                                      | YES     | NO    |
| memory/performance_schema/prepared_statements_instances                        | YES     | NO    |
| memory/performance_schema/rwlock_class                                         | YES     | NO    |
| memory/performance_schema/rwlock_instances                                     | YES     | NO    |
| memory/performance_schema/scalable_buffer                                      | YES     | NO    |
| memory/performance_schema/session_connect_attrs                                | YES     | NO    |
| memory/performance_schema/setup_actors                                         | YES     | NO    |
| memory/performance_schema/setup_objects                                        | YES     | NO    |
| memory/performance_schema/socket_class                                         | YES     | NO    |
| memory/performance_schema/socket_instances                                     | YES     | NO    |
| memory/performance_schema/stage_class                                          | YES     | NO    |
| memory/performance_schema/statement_class                                      | YES     | NO    |
| memory/performance_schema/table_handles                                        | YES     | NO    |
| memory/performance_schema/table_io_waits_summary_by_index_usage                | YES     | NO    |
| memory/performance_schema/table_lock_waits_summary_by_table                    | YES     | NO    |
| memory/performance_schema/table_shares                                         | YES     | NO    |
| memory/performance_schema/threads                                              | YES     | NO    |
| memory/performance_schema/thread_class                                         | YES     | NO    |
| memory/performance_schema/users                                                | YES     | NO    |
| memory/sql/acl_cache                                                           | NO      | NO    |
| memory/sql/binlog_cache_mngr                                                   | NO      | NO    |
| memory/sql/binlog_pos                                                          | NO      | NO    |
| memory/sql/binlog_statement_buffer                                             | NO      | NO    |
| memory/sql/binlog_ver_1_event                                                  | NO      | NO    |
| memory/sql/bison_stack                                                         | NO      | NO    |
| memory/sql/Blob_mem_storage::storage                                           | NO      | NO    |
| memory/sql/DATE_TIME_FORMAT                                                    | NO      | NO    |
| memory/sql/dboptions_hash                                                      | NO      | NO    |
| memory/sql/DDL_LOG_MEMORY_ENTRY                                                | NO      | NO    |
| memory/sql/display_table_locks                                                 | NO      | NO    |
| memory/sql/errmsgs                                                             | NO      | NO    |
| memory/sql/Event_basic::mem_root                                               | NO      | NO    |
| memory/sql/Event_queue_element_for_exec::names                                 | NO      | NO    |
| memory/sql/Event_scheduler::scheduler_param                                    | NO      | NO    |
| memory/sql/Filesort_info::merge                                                | NO      | NO    |
| memory/sql/Filesort_info::record_pointers                                      | NO      | NO    |
| memory/sql/frm::string                                                         | NO      | NO    |
| memory/sql/gdl                                                                 | NO      | NO    |
| memory/sql/Gis_read_stream::err_msg                                            | NO      | NO    |
| memory/sql/global_system_variables                                             | NO      | NO    |
| memory/sql/handler::errmsgs                                                    | NO      | NO    |
| memory/sql/handlerton                                                          | NO      | NO    |
| memory/sql/hash_index_key_buffer                                               | NO      | NO    |
| memory/sql/host_cache::hostname                                                | NO      | NO    |
| memory/sql/ignored_db                                                          | NO      | NO    |
| memory/sql/JOIN_CACHE                                                          | NO      | NO    |
| memory/sql/load_env_plugins                                                    | NO      | NO    |
| memory/sql/Locked_tables_list::m_locked_tables_root                            | NO      | NO    |
| memory/sql/MDL_context::acquire_locks                                          | NO      | NO    |
| memory/sql/MPVIO_EXT::auth_info                                                | NO      | NO    |
| memory/sql/MYSQL_BIN_LOG::basename                                             | NO      | NO    |
| memory/sql/MYSQL_BIN_LOG::index                                                | NO      | NO    |
| memory/sql/MYSQL_BIN_LOG::recover                                              | NO      | NO    |
| memory/sql/MYSQL_LOCK                                                          | NO      | NO    |
| memory/sql/MYSQL_LOG::name                                                     | NO      | NO    |
| memory/sql/mysql_plugin                                                        | NO      | NO    |
| memory/sql/mysql_plugin_dl                                                     | NO      | NO    |
| memory/sql/MYSQL_RELAY_LOG::basename                                           | NO      | NO    |
| memory/sql/MYSQL_RELAY_LOG::index                                              | NO      | NO    |
| memory/sql/my_str_malloc                                                       | NO      | NO    |
| memory/sql/NAMED_ILINK::name                                                   | NO      | NO    |
| memory/sql/native_functions                                                    | NO      | NO    |
| memory/sql/plugin_bookmark                                                     | NO      | NO    |
| memory/sql/plugin_int_mem_root                                                 | NO      | NO    |
| memory/sql/plugin_mem_root                                                     | NO      | NO    |
| memory/sql/Prepared_statement::main_mem_root                                   | NO      | NO    |
| memory/sql/Prepared_statement_map                                              | NO      | NO    |
| memory/sql/PROFILE                                                             | NO      | NO    |
| memory/sql/Query_cache                                                         | NO      | NO    |
| memory/sql/Queue::queue_item                                                   | NO      | NO    |
| memory/sql/QUICK_RANGE_SELECT::alloc                                           | NO      | NO    |
| memory/sql/QUICK_RANGE_SELECT::mrr_buf_desc                                    | NO      | NO    |
| memory/sql/Relay_log_info::group_relay_log_name                                | NO      | NO    |
| memory/sql/root                                                                | NO      | NO    |
| memory/sql/Row_data_memory::memory                                             | NO      | NO    |
| memory/sql/rpl_filter memory                                                   | NO      | NO    |
| memory/sql/Rpl_info_file::buffer                                               | NO      | NO    |
| memory/sql/servers_cache                                                       | NO      | NO    |
| memory/sql/SLAVE_INFO                                                          | NO      | NO    |
| memory/sql/Sort_param::tmp_buffer                                              | NO      | NO    |
| memory/sql/sp_head::call_mem_root                                              | NO      | NO    |
| memory/sql/sp_head::execute_mem_root                                           | NO      | NO    |
| memory/sql/sp_head::main_mem_root                                              | NO      | NO    |
| memory/sql/sql_acl_mem                                                         | NO      | NO    |
| memory/sql/sql_acl_memex                                                       | NO      | NO    |
| memory/sql/String::value                                                       | NO      | NO    |
| memory/sql/ST_SCHEMA_TABLE                                                     | NO      | NO    |
| memory/sql/Sys_var_charptr::value                                              | NO      | NO    |
| memory/sql/TABLE                                                               | NO      | NO    |
| memory/sql/table_mapping::m_mem_root                                           | NO      | NO    |
| memory/sql/TABLE_RULE_ENT                                                      | NO      | NO    |
| memory/sql/TABLE_SHARE::mem_root                                               | NO      | NO    |
| memory/sql/Table_triggers_list                                                 | NO      | NO    |
| memory/sql/Table_trigger_dispatcher::m_mem_root                                | NO      | NO    |
| memory/sql/TC_LOG_MMAP::pages                                                  | NO      | NO    |
| memory/sql/THD::db                                                             | NO      | NO    |
| memory/sql/THD::handler_tables_hash                                            | NO      | NO    |
| memory/sql/thd::main_mem_root                                                  | NO      | NO    |
| memory/sql/THD::sp_cache                                                       | NO      | NO    |
| memory/sql/THD::transactions::mem_root                                         | NO      | NO    |
| memory/sql/THD::variables                                                      | NO      | NO    |
| memory/sql/tz_storage                                                          | NO      | NO    |
| memory/sql/udf_mem                                                             | NO      | NO    |
| memory/sql/Unique::merge_buffer                                                | NO      | NO    |
| memory/sql/Unique::sort_buffer                                                 | NO      | NO    |
| memory/sql/user_conn                                                           | NO      | NO    |
| memory/sql/User_level_lock                                                     | NO      | NO    |
| memory/sql/user_var_entry                                                      | NO      | NO    |
| memory/sql/user_var_entry::value                                               | NO      | NO    |
| memory/sql/XID                                                                 | NO      | NO    |
| stage/aria/Waiting for a resource                                              | NO      | NO    |
| stage/innodb/alter table (end)                                                 | YES     | YES   |
| stage/innodb/alter table (insert)                                              | YES     | YES   |
| stage/innodb/alter table (log apply index)                                     | YES     | YES   |
| stage/innodb/alter table (log apply table)                                     | YES     | YES   |
| stage/innodb/alter table (merge sort)                                          | YES     | YES   |
| stage/innodb/alter table (read PK and internal sort)                           | YES     | YES   |
| stage/innodb/buffer pool load                                                  | YES     | YES   |
| stage/mysys/Waiting for table level lock                                       | NO      | NO    |
| stage/sql/After apply log event                                                | NO      | NO    |
| stage/sql/After create                                                         | NO      | NO    |
| stage/sql/After opening tables                                                 | NO      | NO    |
| stage/sql/After table lock                                                     | NO      | NO    |
| stage/sql/Allocating local table                                               | NO      | NO    |
| stage/sql/altering table                                                       | NO      | NO    |
| stage/sql/Apply log event                                                      | NO      | NO    |
| stage/sql/Changing master                                                      | NO      | NO    |
| stage/sql/Checking master version                                              | NO      | NO    |
| stage/sql/checking permissions                                                 | NO      | NO    |
| stage/sql/checking privileges on cached query                                  | NO      | NO    |
| stage/sql/Checking query cache for query                                       | NO      | NO    |
| stage/sql/closing tables                                                       | NO      | NO    |
| stage/sql/Commit                                                               | NO      | NO    |
| stage/sql/Commit implicit                                                      | NO      | NO    |
| stage/sql/Committing alter table to storage engine                             | NO      | NO    |
| stage/sql/Connecting to master                                                 | NO      | NO    |
| stage/sql/Converting HEAP to Aria                                              | NO      | NO    |
| stage/sql/copy to tmp table                                                    | YES     | YES   |
| stage/sql/Copying to group table                                               | NO      | NO    |
| stage/sql/Copying to tmp table                                                 | NO      | NO    |
| stage/sql/Creating delayed handler                                             | NO      | NO    |
| stage/sql/Creating sort index                                                  | NO      | NO    |
| stage/sql/creating table                                                       | NO      | NO    |
| stage/sql/Creating tmp table                                                   | NO      | NO    |
| stage/sql/Deleting from main table                                             | NO      | NO    |
| stage/sql/Deleting from reference tables                                       | NO      | NO    |
| stage/sql/Discard_or_import_tablespace                                         | NO      | NO    |
| stage/sql/Enabling keys                                                        | NO      | NO    |
| stage/sql/End of update loop                                                   | NO      | NO    |
| stage/sql/Executing                                                            | NO      | NO    |
| stage/sql/Execution of init_command                                            | NO      | NO    |
| stage/sql/Explaining                                                           | NO      | NO    |
| stage/sql/Filling schema table                                                 | NO      | NO    |
| stage/sql/Finding key cache                                                    | NO      | NO    |
| stage/sql/Finished reading one binlog; switching to next binlog                | NO      | NO    |
| stage/sql/Flushing relay log and master info repository.                       | NO      | NO    |
| stage/sql/Flushing relay-log info file.                                        | NO      | NO    |
| stage/sql/Freeing items                                                        | NO      | NO    |
| stage/sql/Fulltext initialization                                              | NO      | NO    |
| stage/sql/Got handler lock                                                     | NO      | NO    |
| stage/sql/Got old table                                                        | NO      | NO    |
| stage/sql/init                                                                 | NO      | NO    |
| stage/sql/init for update                                                      | NO      | NO    |
| stage/sql/Insert                                                               | NO      | NO    |
| stage/sql/Invalidating query cache entries (table list)                        | NO      | NO    |
| stage/sql/Invalidating query cache entries (table)                             | NO      | NO    |
| stage/sql/Killing slave                                                        | NO      | NO    |
| stage/sql/Logging slow query                                                   | NO      | NO    |
| stage/sql/Making temporary file (append) before replaying LOAD DATA INFILE     | NO      | NO    |
| stage/sql/Making temporary file (create) before replaying LOAD DATA INFILE     | NO      | NO    |
| stage/sql/Manage keys                                                          | NO      | NO    |
| stage/sql/Master has sent all binlog to slave; waiting for more updates        | NO      | NO    |
| stage/sql/Opening tables                                                       | NO      | NO    |
| stage/sql/Optimizing                                                           | NO      | NO    |
| stage/sql/Preparing                                                            | NO      | NO    |
| stage/sql/preparing for alter table                                            | NO      | NO    |
| stage/sql/Processing binlog checkpoint notification                            | NO      | NO    |
| stage/sql/Processing requests                                                  | NO      | NO    |
| stage/sql/Purging old relay logs                                               | NO      | NO    |
| stage/sql/Query end                                                            | NO      | NO    |
| stage/sql/Queueing master event to the relay log                               | NO      | NO    |
| stage/sql/Reading event from the relay log                                     | NO      | NO    |
| stage/sql/Reading semi-sync ACK from slave                                     | NO      | NO    |
| stage/sql/Recreating table                                                     | NO      | NO    |
| stage/sql/Registering slave on master                                          | NO      | NO    |
| stage/sql/Removing duplicates                                                  | NO      | NO    |
| stage/sql/Removing tmp table                                                   | NO      | NO    |
| stage/sql/Rename                                                               | NO      | NO    |
| stage/sql/Rename result table                                                  | NO      | NO    |
| stage/sql/Requesting binlog dump                                               | NO      | NO    |
| stage/sql/Reschedule                                                           | NO      | NO    |
| stage/sql/Reset for next command                                               | NO      | NO    |
| stage/sql/Rollback                                                             | NO      | NO    |
| stage/sql/Rollback_implicit                                                    | NO      | NO    |
| stage/sql/Searching rows for update                                            | NO      | NO    |
| stage/sql/Sending binlog event to slave                                        | NO      | NO    |
| stage/sql/Sending cached result to client                                      | NO      | NO    |
| stage/sql/Sending data                                                         | NO      | NO    |
| stage/sql/setup                                                                | NO      | NO    |
| stage/sql/Show explain                                                         | NO      | NO    |
| stage/sql/Slave has read all relay log; waiting for more updates               | NO      | NO    |
| stage/sql/Sorting                                                              | NO      | NO    |
| stage/sql/Sorting for group                                                    | NO      | NO    |
| stage/sql/Sorting for order                                                    | NO      | NO    |
| stage/sql/Sorting result                                                       | NO      | NO    |
| stage/sql/starting                                                             | NO      | NO    |
| stage/sql/Starting cleanup                                                     | NO      | NO    |
| stage/sql/Statistics                                                           | NO      | NO    |
| stage/sql/Stopping binlog background thread                                    | NO      | NO    |
| stage/sql/Storing result in query cache                                        | NO      | NO    |
| stage/sql/Storing row into queue                                               | NO      | NO    |
| stage/sql/System lock                                                          | NO      | NO    |
| stage/sql/table lock                                                           | NO      | NO    |
| stage/sql/Unlocking tables                                                     | NO      | NO    |
| stage/sql/Update                                                               | NO      | NO    |
| stage/sql/Updating                                                             | NO      | NO    |
| stage/sql/Updating main table                                                  | NO      | NO    |
| stage/sql/Updating reference tables                                            | NO      | NO    |
| stage/sql/Upgrading lock                                                       | NO      | NO    |
| stage/sql/User lock                                                            | NO      | NO    |
| stage/sql/User sleep                                                           | NO      | NO    |
| stage/sql/Verifying table                                                      | NO      | NO    |
| stage/sql/Waiting for background binlog tasks                                  | NO      | NO    |
| stage/sql/Waiting for backup lock                                              | NO      | NO    |
| stage/sql/Waiting for delay_list                                               | NO      | NO    |
| stage/sql/Waiting for event metadata lock                                      | NO      | NO    |
| stage/sql/Waiting for GTID to be written to binary log                         | NO      | NO    |
| stage/sql/Waiting for handler insert                                           | NO      | NO    |
| stage/sql/Waiting for handler lock                                             | NO      | NO    |
| stage/sql/Waiting for handler open                                             | NO      | NO    |
| stage/sql/Waiting for INSERT                                                   | NO      | NO    |
| stage/sql/Waiting for master to send event                                     | NO      | NO    |
| stage/sql/Waiting for master update                                            | NO      | NO    |
| stage/sql/Waiting for next activation                                          | NO      | NO    |
| stage/sql/Waiting for other master connection to process the same GTID         | NO      | NO    |
| stage/sql/Waiting for parallel replication deadlock handling to complete       | NO      | NO    |
| stage/sql/Waiting for prior transaction to commit                              | NO      | NO    |
| stage/sql/Waiting for prior transaction to start commit                        | NO      | NO    |
| stage/sql/Waiting for query cache lock                                         | NO      | NO    |
| stage/sql/Waiting for requests                                                 | NO      | NO    |
| stage/sql/Waiting for room in worker thread event queue                        | NO      | NO    |
| stage/sql/Waiting for schema metadata lock                                     | NO      | NO    |
| stage/sql/Waiting for semi-sync ACK from slave                                 | NO      | NO    |
| stage/sql/Waiting for semi-sync slave connection                               | NO      | NO    |
| stage/sql/Waiting for slave mutex on exit                                      | NO      | NO    |
| stage/sql/Waiting for slave thread to start                                    | NO      | NO    |
| stage/sql/Waiting for stored function metadata lock                            | NO      | NO    |
| stage/sql/Waiting for stored package body metadata lock                        | NO      | NO    |
| stage/sql/Waiting for stored procedure metadata lock                           | NO      | NO    |
| stage/sql/Waiting for table flush                                              | NO      | NO    |
| stage/sql/Waiting for table metadata lock                                      | NO      | NO    |
| stage/sql/Waiting for the next event in relay log                              | NO      | NO    |
| stage/sql/Waiting for the scheduler to stop                                    | NO      | NO    |
| stage/sql/Waiting for the slave SQL thread to advance position                 | NO      | NO    |
| stage/sql/Waiting for the slave SQL thread to free enough relay log space      | NO      | NO    |
| stage/sql/Waiting for trigger metadata lock                                    | NO      | NO    |
| stage/sql/Waiting for work from SQL thread                                     | NO      | NO    |
| stage/sql/Waiting in MASTER_GTID_WAIT()                                        | NO      | NO    |
| stage/sql/Waiting in MASTER_GTID_WAIT() (primary waiter)                       | NO      | NO    |
| stage/sql/Waiting on empty queue                                               | NO      | NO    |
| stage/sql/Waiting to finalize termination                                      | NO      | NO    |
| stage/sql/Waiting until MASTER_DELAY seconds after master executed event       | NO      | NO    |
| stage/sql/Writing to binlog                                                    | NO      | NO    |
| statement/abstract/new_packet                                                  | YES     | YES   |
| statement/abstract/Query                                                       | YES     | YES   |
| statement/abstract/relay_log                                                   | YES     | YES   |
| statement/com/Binlog Dump                                                      | YES     | YES   |
| statement/com/Bulk_execute                                                     | YES     | YES   |
| statement/com/Change user                                                      | YES     | YES   |
| statement/com/Close stmt                                                       | YES     | YES   |
| statement/com/Com_multi                                                        | YES     | YES   |
| statement/com/Connect                                                          | YES     | YES   |
| statement/com/Connect Out                                                      | YES     | YES   |
| statement/com/Create DB                                                        | YES     | YES   |
| statement/com/Daemon                                                           | YES     | YES   |
| statement/com/Debug                                                            | YES     | YES   |
| statement/com/Delayed insert                                                   | YES     | YES   |
| statement/com/Drop DB                                                          | YES     | YES   |
| statement/com/Error                                                            | YES     | YES   |
| statement/com/Execute                                                          | YES     | YES   |
| statement/com/Fetch                                                            | YES     | YES   |
| statement/com/Field List                                                       | YES     | YES   |
| statement/com/Init DB                                                          | YES     | YES   |
| statement/com/Kill                                                             | YES     | YES   |
| statement/com/Long Data                                                        | YES     | YES   |
| statement/com/Ping                                                             | YES     | YES   |
| statement/com/Prepare                                                          | YES     | YES   |
| statement/com/Processlist                                                      | YES     | YES   |
| statement/com/Quit                                                             | YES     | YES   |
| statement/com/Refresh                                                          | YES     | YES   |
| statement/com/Register Slave                                                   | YES     | YES   |
| statement/com/Reset connection                                                 | YES     | YES   |
| statement/com/Reset stmt                                                       | YES     | YES   |
| statement/com/Set option                                                       | YES     | YES   |
| statement/com/Shutdown                                                         | YES     | YES   |
| statement/com/Slave_IO                                                         | YES     | YES   |
| statement/com/Slave_SQL                                                        | YES     | YES   |
| statement/com/Slave_worker                                                     | YES     | YES   |
| statement/com/Sleep                                                            | YES     | YES   |
| statement/com/Statistics                                                       | YES     | YES   |
| statement/com/Table Dump                                                       | YES     | YES   |
| statement/com/Time                                                             | YES     | YES   |
| statement/com/Unimpl get tid                                                   | YES     | YES   |
| statement/scheduler/event                                                      | YES     | YES   |
| statement/sp/agg_cfetch                                                        | YES     | YES   |
| statement/sp/cclose                                                            | YES     | YES   |
| statement/sp/cfetch                                                            | YES     | YES   |
| statement/sp/copen                                                             | YES     | YES   |
| statement/sp/cpop                                                              | YES     | YES   |
| statement/sp/cpush                                                             | YES     | YES   |
| statement/sp/cursor_copy_struct                                                | YES     | YES   |
| statement/sp/error                                                             | YES     | YES   |
| statement/sp/freturn                                                           | YES     | YES   |
| statement/sp/hpop                                                              | YES     | YES   |
| statement/sp/hpush_jump                                                        | YES     | YES   |
| statement/sp/hreturn                                                           | YES     | YES   |
| statement/sp/jump                                                              | YES     | YES   |
| statement/sp/jump_if_not                                                       | YES     | YES   |
| statement/sp/preturn                                                           | YES     | YES   |
| statement/sp/set                                                               | YES     | YES   |
| statement/sp/set_case_expr                                                     | YES     | YES   |
| statement/sp/set_trigger_field                                                 | YES     | YES   |
| statement/sp/stmt                                                              | YES     | YES   |
| statement/sql/                                                                 | YES     | YES   |
| statement/sql/alter_db                                                         | YES     | YES   |
| statement/sql/alter_db_upgrade                                                 | YES     | YES   |
| statement/sql/alter_event                                                      | YES     | YES   |
| statement/sql/alter_function                                                   | YES     | YES   |
| statement/sql/alter_procedure                                                  | YES     | YES   |
| statement/sql/alter_sequence                                                   | YES     | YES   |
| statement/sql/alter_server                                                     | YES     | YES   |
| statement/sql/alter_table                                                      | YES     | YES   |
| statement/sql/alter_tablespace                                                 | YES     | YES   |
| statement/sql/alter_user                                                       | YES     | YES   |
| statement/sql/analyze                                                          | YES     | YES   |
| statement/sql/assign_to_keycache                                               | YES     | YES   |
| statement/sql/backup                                                           | YES     | YES   |
| statement/sql/backup_lock                                                      | YES     | YES   |
| statement/sql/begin                                                            | YES     | YES   |
| statement/sql/binlog                                                           | YES     | YES   |
| statement/sql/call_procedure                                                   | YES     | YES   |
| statement/sql/change_db                                                        | YES     | YES   |
| statement/sql/change_master                                                    | YES     | YES   |
| statement/sql/check                                                            | YES     | YES   |
| statement/sql/checksum                                                         | YES     | YES   |
| statement/sql/commit                                                           | YES     | YES   |
| statement/sql/compound_sql                                                     | YES     | YES   |
| statement/sql/create_db                                                        | YES     | YES   |
| statement/sql/create_event                                                     | YES     | YES   |
| statement/sql/create_function                                                  | YES     | YES   |
| statement/sql/create_index                                                     | YES     | YES   |
| statement/sql/create_package                                                   | YES     | YES   |
| statement/sql/create_package_body                                              | YES     | YES   |
| statement/sql/create_procedure                                                 | YES     | YES   |
| statement/sql/create_role                                                      | YES     | YES   |
| statement/sql/create_sequence                                                  | YES     | YES   |
| statement/sql/create_server                                                    | YES     | YES   |
| statement/sql/create_table                                                     | YES     | YES   |
| statement/sql/create_trigger                                                   | YES     | YES   |
| statement/sql/create_udf                                                       | YES     | YES   |
| statement/sql/create_user                                                      | YES     | YES   |
| statement/sql/create_view                                                      | YES     | YES   |
| statement/sql/dealloc_sql                                                      | YES     | YES   |
| statement/sql/delete                                                           | YES     | YES   |
| statement/sql/delete_multi                                                     | YES     | YES   |
| statement/sql/do                                                               | YES     | YES   |
| statement/sql/drop_db                                                          | YES     | YES   |
| statement/sql/drop_event                                                       | YES     | YES   |
| statement/sql/drop_function                                                    | YES     | YES   |
| statement/sql/drop_index                                                       | YES     | YES   |
| statement/sql/drop_package                                                     | YES     | YES   |
| statement/sql/drop_package_body                                                | YES     | YES   |
| statement/sql/drop_procedure                                                   | YES     | YES   |
| statement/sql/drop_role                                                        | YES     | YES   |
| statement/sql/drop_sequence                                                    | YES     | YES   |
| statement/sql/drop_server                                                      | YES     | YES   |
| statement/sql/drop_table                                                       | YES     | YES   |
| statement/sql/drop_trigger                                                     | YES     | YES   |
| statement/sql/drop_user                                                        | YES     | YES   |
| statement/sql/drop_view                                                        | YES     | YES   |
| statement/sql/empty_query                                                      | YES     | YES   |
| statement/sql/error                                                            | YES     | YES   |
| statement/sql/execute_immediate                                                | YES     | YES   |
| statement/sql/execute_sql                                                      | YES     | YES   |
| statement/sql/flush                                                            | YES     | YES   |
| statement/sql/get_diagnostics                                                  | YES     | YES   |
| statement/sql/grant                                                            | YES     | YES   |
| statement/sql/grant_role                                                       | YES     | YES   |
| statement/sql/ha_close                                                         | YES     | YES   |
| statement/sql/ha_open                                                          | YES     | YES   |
| statement/sql/ha_read                                                          | YES     | YES   |
| statement/sql/help                                                             | YES     | YES   |
| statement/sql/insert                                                           | YES     | YES   |
| statement/sql/insert_select                                                    | YES     | YES   |
| statement/sql/install_plugin                                                   | YES     | YES   |
| statement/sql/kill                                                             | YES     | YES   |
| statement/sql/load                                                             | YES     | YES   |
| statement/sql/lock_tables                                                      | YES     | YES   |
| statement/sql/optimize                                                         | YES     | YES   |
| statement/sql/preload_keys                                                     | YES     | YES   |
| statement/sql/prepare_sql                                                      | YES     | YES   |
| statement/sql/purge                                                            | YES     | YES   |
| statement/sql/purge_before_date                                                | YES     | YES   |
| statement/sql/release_savepoint                                                | YES     | YES   |
| statement/sql/rename_table                                                     | YES     | YES   |
| statement/sql/rename_user                                                      | YES     | YES   |
| statement/sql/repair                                                           | YES     | YES   |
| statement/sql/replace                                                          | YES     | YES   |
| statement/sql/replace_select                                                   | YES     | YES   |
| statement/sql/reset                                                            | YES     | YES   |
| statement/sql/resignal                                                         | YES     | YES   |
| statement/sql/revoke                                                           | YES     | YES   |
| statement/sql/revoke_all                                                       | YES     | YES   |
| statement/sql/revoke_role                                                      | YES     | YES   |
| statement/sql/rollback                                                         | YES     | YES   |
| statement/sql/rollback_to_savepoint                                            | YES     | YES   |
| statement/sql/savepoint                                                        | YES     | YES   |
| statement/sql/select                                                           | YES     | YES   |
| statement/sql/set_option                                                       | YES     | YES   |
| statement/sql/show_authors                                                     | YES     | YES   |
| statement/sql/show_binlogs                                                     | YES     | YES   |
| statement/sql/show_binlog_events                                               | YES     | YES   |
| statement/sql/show_binlog_status                                               | YES     | YES   |
| statement/sql/show_charsets                                                    | YES     | YES   |
| statement/sql/show_collations                                                  | YES     | YES   |
| statement/sql/show_contributors                                                | YES     | YES   |
| statement/sql/show_create_db                                                   | YES     | YES   |
| statement/sql/show_create_event                                                | YES     | YES   |
| statement/sql/show_create_func                                                 | YES     | YES   |
| statement/sql/show_create_package                                              | YES     | YES   |
| statement/sql/show_create_package_body                                         | YES     | YES   |
| statement/sql/show_create_proc                                                 | YES     | YES   |
| statement/sql/show_create_table                                                | YES     | YES   |
| statement/sql/show_create_trigger                                              | YES     | YES   |
| statement/sql/show_create_user                                                 | YES     | YES   |
| statement/sql/show_databases                                                   | YES     | YES   |
| statement/sql/show_engine_logs                                                 | YES     | YES   |
| statement/sql/show_engine_mutex                                                | YES     | YES   |
| statement/sql/show_engine_status                                               | YES     | YES   |
| statement/sql/show_errors                                                      | YES     | YES   |
| statement/sql/show_events                                                      | YES     | YES   |
| statement/sql/show_explain                                                     | YES     | YES   |
| statement/sql/show_fields                                                      | YES     | YES   |
| statement/sql/show_function_status                                             | YES     | YES   |
| statement/sql/show_generic                                                     | YES     | YES   |
| statement/sql/show_grants                                                      | YES     | YES   |
| statement/sql/show_keys                                                        | YES     | YES   |
| statement/sql/show_open_tables                                                 | YES     | YES   |
| statement/sql/show_package_body_status                                         | YES     | YES   |
| statement/sql/show_package_status                                              | YES     | YES   |
| statement/sql/show_plugins                                                     | YES     | YES   |
| statement/sql/show_privileges                                                  | YES     | YES   |
| statement/sql/show_procedure_status                                            | YES     | YES   |
| statement/sql/show_processlist                                                 | YES     | YES   |
| statement/sql/show_profile                                                     | YES     | YES   |
| statement/sql/show_profiles                                                    | YES     | YES   |
| statement/sql/show_relaylog_events                                             | YES     | YES   |
| statement/sql/show_slave_hosts                                                 | YES     | YES   |
| statement/sql/show_slave_status                                                | YES     | YES   |
| statement/sql/show_status                                                      | YES     | YES   |
| statement/sql/show_storage_engines                                             | YES     | YES   |
| statement/sql/show_tables                                                      | YES     | YES   |
| statement/sql/show_table_status                                                | YES     | YES   |
| statement/sql/show_triggers                                                    | YES     | YES   |
| statement/sql/show_variables                                                   | YES     | YES   |
| statement/sql/show_warnings                                                    | YES     | YES   |
| statement/sql/shutdown                                                         | YES     | YES   |
| statement/sql/signal                                                           | YES     | YES   |
| statement/sql/start_all_slaves                                                 | YES     | YES   |
| statement/sql/start_slave                                                      | YES     | YES   |
| statement/sql/stop_all_slaves                                                  | YES     | YES   |
| statement/sql/stop_slave                                                       | YES     | YES   |
| statement/sql/truncate                                                         | YES     | YES   |
| statement/sql/uninstall_plugin                                                 | YES     | YES   |
| statement/sql/unlock_tables                                                    | YES     | YES   |
| statement/sql/update                                                           | YES     | YES   |
| statement/sql/update_multi                                                     | YES     | YES   |
| statement/sql/xa_commit                                                        | YES     | YES   |
| statement/sql/xa_end                                                           | YES     | YES   |
| statement/sql/xa_prepare                                                       | YES     | YES   |
| statement/sql/xa_recover                                                       | YES     | YES   |
| statement/sql/xa_rollback                                                      | YES     | YES   |
| statement/sql/xa_start                                                         | YES     | YES   |
| transaction                                                                    | NO      | NO    |
| wait/io/file/aria/control                                                      | YES     | YES   |
| wait/io/file/aria/MAD                                                          | YES     | YES   |
| wait/io/file/aria/MAI                                                          | YES     | YES   |
| wait/io/file/aria/translog                                                     | YES     | YES   |
| wait/io/file/csv/data                                                          | YES     | YES   |
| wait/io/file/csv/metadata                                                      | YES     | YES   |
| wait/io/file/csv/update                                                        | YES     | YES   |
| wait/io/file/innodb/innodb_data_file                                           | YES     | YES   |
| wait/io/file/innodb/innodb_log_file                                            | YES     | YES   |
| wait/io/file/innodb/innodb_temp_file                                           | YES     | YES   |
| wait/io/file/myisam/data_tmp                                                   | YES     | YES   |
| wait/io/file/myisam/dfile                                                      | YES     | YES   |
| wait/io/file/myisam/kfile                                                      | YES     | YES   |
| wait/io/file/myisam/log                                                        | YES     | YES   |
| wait/io/file/myisammrg/MRG                                                     | YES     | YES   |
| wait/io/file/mysys/charset                                                     | YES     | YES   |
| wait/io/file/mysys/cnf                                                         | YES     | YES   |
| wait/io/file/partition/ha_partition::parfile                                   | YES     | YES   |
| wait/io/file/sql/binlog                                                        | YES     | YES   |
| wait/io/file/sql/binlog_cache                                                  | YES     | YES   |
| wait/io/file/sql/binlog_index                                                  | YES     | YES   |
| wait/io/file/sql/binlog_index_cache                                            | YES     | YES   |
| wait/io/file/sql/binlog_state                                                  | YES     | YES   |
| wait/io/file/sql/casetest                                                      | YES     | YES   |
| wait/io/file/sql/dbopt                                                         | YES     | YES   |
| wait/io/file/sql/des_key_file                                                  | YES     | YES   |
| wait/io/file/sql/ERRMSG                                                        | YES     | YES   |
| wait/io/file/sql/file_parser                                                   | YES     | YES   |
| wait/io/file/sql/FRM                                                           | YES     | YES   |
| wait/io/file/sql/global_ddl_log                                                | YES     | YES   |
| wait/io/file/sql/init                                                          | YES     | YES   |
| wait/io/file/sql/io_cache                                                      | YES     | YES   |
| wait/io/file/sql/load                                                          | YES     | YES   |
| wait/io/file/sql/LOAD_FILE                                                     | YES     | YES   |
| wait/io/file/sql/log_event_data                                                | YES     | YES   |
| wait/io/file/sql/log_event_info                                                | YES     | YES   |
| wait/io/file/sql/map                                                           | YES     | YES   |
| wait/io/file/sql/master_info                                                   | YES     | YES   |
| wait/io/file/sql/misc                                                          | YES     | YES   |
| wait/io/file/sql/partition_ddl_log                                             | YES     | YES   |
| wait/io/file/sql/pid                                                           | YES     | YES   |
| wait/io/file/sql/query_log                                                     | YES     | YES   |
| wait/io/file/sql/relaylog                                                      | YES     | YES   |
| wait/io/file/sql/relaylog_cache                                                | YES     | YES   |
| wait/io/file/sql/relaylog_index                                                | YES     | YES   |
| wait/io/file/sql/relaylog_index_cache                                          | YES     | YES   |
| wait/io/file/sql/relay_log_info                                                | YES     | YES   |
| wait/io/file/sql/select_to_file                                                | YES     | YES   |
| wait/io/file/sql/send_file                                                     | YES     | YES   |
| wait/io/file/sql/slow_log                                                      | YES     | YES   |
| wait/io/file/sql/tclog                                                         | YES     | YES   |
| wait/io/file/sql/trigger                                                       | YES     | YES   |
| wait/io/file/sql/trigger_name                                                  | YES     | YES   |
| wait/io/file/sql/wsrep_gra_log                                                 | YES     | YES   |
| wait/io/socket/sql/client_connection                                           | NO      | NO    |
| wait/io/socket/sql/server_tcpip_socket                                         | NO      | NO    |
| wait/io/socket/sql/server_unix_socket                                          | NO      | NO    |
| wait/io/table/sql/handler                                                      | YES     | YES   |
| wait/lock/metadata/sql/mdl                                                     | NO      | NO    |
| wait/lock/table/sql/handler                                                    | YES     | YES   |
| wait/synch/cond/aria/BITMAP::bitmap_cond                                       | NO      | NO    |
| wait/synch/cond/aria/COND_soft_sync                                            | NO      | NO    |
| wait/synch/cond/aria/SERVICE_THREAD_CONTROL::COND_control                      | NO      | NO    |
| wait/synch/cond/aria/SHARE::key_del_cond                                       | NO      | NO    |
| wait/synch/cond/aria/SORT_INFO::cond                                           | NO      | NO    |
| wait/synch/cond/aria/TRANSLOG_BUFFER::prev_sent_to_disk_cond                   | NO      | NO    |
| wait/synch/cond/aria/TRANSLOG_BUFFER::waiting_filling_buffer                   | NO      | NO    |
| wait/synch/cond/aria/TRANSLOG_DESCRIPTOR::log_flush_cond                       | NO      | NO    |
| wait/synch/cond/aria/TRANSLOG_DESCRIPTOR::new_goal_cond                        | NO      | NO    |
| wait/synch/cond/innodb/commit_cond                                             | NO      | NO    |
| wait/synch/cond/myisam/MI_SORT_INFO::cond                                      | NO      | NO    |
| wait/synch/cond/mysys/COND_alarm                                               | NO      | NO    |
| wait/synch/cond/mysys/COND_timer                                               | NO      | NO    |
| wait/synch/cond/mysys/IO_CACHE_SHARE::cond                                     | NO      | NO    |
| wait/synch/cond/mysys/IO_CACHE_SHARE::cond_writer                              | NO      | NO    |
| wait/synch/cond/mysys/my_thread_var::suspend                                   | NO      | NO    |
| wait/synch/cond/mysys/THR_COND_threads                                         | NO      | NO    |
| wait/synch/cond/mysys/WT_RESOURCE::cond                                        | NO      | NO    |
| wait/synch/cond/sql/Ack_receiver::cond                                         | NO      | NO    |
| wait/synch/cond/sql/COND_binlog_send                                           | NO      | NO    |
| wait/synch/cond/sql/COND_flush_thread_cache                                    | NO      | NO    |
| wait/synch/cond/sql/COND_group_commit_orderer                                  | NO      | NO    |
| wait/synch/cond/sql/COND_gtid_ignore_duplicates                                | NO      | NO    |
| wait/synch/cond/sql/COND_manager                                               | NO      | NO    |
| wait/synch/cond/sql/COND_parallel_entry                                        | NO      | NO    |
| wait/synch/cond/sql/COND_prepare_ordered                                       | NO      | NO    |
| wait/synch/cond/sql/COND_queue_state                                           | NO      | NO    |
| wait/synch/cond/sql/COND_rpl_thread                                            | NO      | NO    |
| wait/synch/cond/sql/COND_rpl_thread_pool                                       | NO      | NO    |
| wait/synch/cond/sql/COND_rpl_thread_queue                                      | NO      | NO    |
| wait/synch/cond/sql/COND_rpl_thread_stop                                       | NO      | NO    |
| wait/synch/cond/sql/COND_server_started                                        | NO      | NO    |
| wait/synch/cond/sql/COND_slave_background                                      | NO      | NO    |
| wait/synch/cond/sql/COND_start_thread                                          | NO      | NO    |
| wait/synch/cond/sql/COND_thread_cache                                          | NO      | NO    |
| wait/synch/cond/sql/COND_wait_gtid                                             | NO      | NO    |
| wait/synch/cond/sql/COND_wsrep_donor_monitor                                   | NO      | NO    |
| wait/synch/cond/sql/COND_wsrep_gtid_wait_upto                                  | NO      | NO    |
| wait/synch/cond/sql/COND_wsrep_joiner_monitor                                  | NO      | NO    |
| wait/synch/cond/sql/COND_wsrep_ready                                           | NO      | NO    |
| wait/synch/cond/sql/COND_wsrep_replaying                                       | NO      | NO    |
| wait/synch/cond/sql/COND_wsrep_sst                                             | NO      | NO    |
| wait/synch/cond/sql/COND_wsrep_sst_init                                        | NO      | NO    |
| wait/synch/cond/sql/COND_wsrep_wsrep_slave_threads                             | NO      | NO    |
| wait/synch/cond/sql/Delayed_insert::cond                                       | NO      | NO    |
| wait/synch/cond/sql/Delayed_insert::cond_client                                | NO      | NO    |
| wait/synch/cond/sql/Event_scheduler::COND_state                                | NO      | NO    |
| wait/synch/cond/sql/Item_func_sleep::cond                                      | NO      | NO    |
| wait/synch/cond/sql/Master_info::data_cond                                     | NO      | NO    |
| wait/synch/cond/sql/Master_info::sleep_cond                                    | NO      | NO    |
| wait/synch/cond/sql/Master_info::start_cond                                    | NO      | NO    |
| wait/synch/cond/sql/Master_info::stop_cond                                     | NO      | NO    |
| wait/synch/cond/sql/MDL_context::COND_wait_status                              | NO      | NO    |
| wait/synch/cond/sql/MYSQL_BIN_LOG::COND_binlog_background_thread               | NO      | NO    |
| wait/synch/cond/sql/MYSQL_BIN_LOG::COND_binlog_background_thread_end           | NO      | NO    |
| wait/synch/cond/sql/MYSQL_BIN_LOG::COND_bin_log_updated                        | NO      | NO    |
| wait/synch/cond/sql/MYSQL_BIN_LOG::COND_queue_busy                             | NO      | NO    |
| wait/synch/cond/sql/MYSQL_BIN_LOG::COND_relay_log_updated                      | NO      | NO    |
| wait/synch/cond/sql/MYSQL_BIN_LOG::COND_xid_list                               | NO      | NO    |
| wait/synch/cond/sql/MYSQL_RELAY_LOG::COND_bin_log_updated                      | NO      | NO    |
| wait/synch/cond/sql/MYSQL_RELAY_LOG::COND_queue_busy                           | NO      | NO    |
| wait/synch/cond/sql/MYSQL_RELAY_LOG::COND_relay_log_updated                    | NO      | NO    |
| wait/synch/cond/sql/PAGE::cond                                                 | NO      | NO    |
| wait/synch/cond/sql/Query_cache::COND_cache_status_changed                     | NO      | NO    |
| wait/synch/cond/sql/Relay_log_info::data_cond                                  | NO      | NO    |
| wait/synch/cond/sql/Relay_log_info::log_space_cond                             | NO      | NO    |
| wait/synch/cond/sql/Relay_log_info::start_cond                                 | NO      | NO    |
| wait/synch/cond/sql/Relay_log_info::stop_cond                                  | NO      | NO    |
| wait/synch/cond/sql/Rpl_group_info::sleep_cond                                 | NO      | NO    |
| wait/synch/cond/sql/show_explain                                               | NO      | NO    |
| wait/synch/cond/sql/TABLE_SHARE::cond                                          | NO      | NO    |
| wait/synch/cond/sql/TABLE_SHARE::COND_rotation                                 | NO      | NO    |
| wait/synch/cond/sql/TABLE_SHARE::tdc.COND_release                              | NO      | NO    |
| wait/synch/cond/sql/TC_LOG_MMAP::COND_active                                   | NO      | NO    |
| wait/synch/cond/sql/TC_LOG_MMAP::COND_pool                                     | NO      | NO    |
| wait/synch/cond/sql/TC_LOG_MMAP::COND_queue_busy                               | NO      | NO    |
| wait/synch/cond/sql/THD::COND_wakeup_ready                                     | NO      | NO    |
| wait/synch/cond/sql/THD::COND_wsrep_thd                                        | NO      | NO    |
| wait/synch/cond/sql/User_level_lock::cond                                      | NO      | NO    |
| wait/synch/cond/sql/wait_for_commit::COND_wait_commit                          | NO      | NO    |
| wait/synch/cond/sql/wsrep_sst_thread                                           | NO      | NO    |
| wait/synch/mutex/aria/LOCK_soft_sync                                           | NO      | NO    |
| wait/synch/mutex/aria/LOCK_trn_list                                            | NO      | NO    |
| wait/synch/mutex/aria/PAGECACHE::cache_lock                                    | NO      | NO    |
| wait/synch/mutex/aria/SERVICE_THREAD_CONTROL::LOCK_control                     | NO      | NO    |
| wait/synch/mutex/aria/SHARE::bitmap::bitmap_lock                               | NO      | NO    |
| wait/synch/mutex/aria/SHARE::close_lock                                        | NO      | NO    |
| wait/synch/mutex/aria/SHARE::intern_lock                                       | NO      | NO    |
| wait/synch/mutex/aria/SHARE::key_del_lock                                      | NO      | NO    |
| wait/synch/mutex/aria/SORT_INFO::mutex                                         | NO      | NO    |
| wait/synch/mutex/aria/THR_LOCK_maria                                           | NO      | NO    |
| wait/synch/mutex/aria/TRANSLOG_BUFFER::mutex                                   | NO      | NO    |
| wait/synch/mutex/aria/TRANSLOG_DESCRIPTOR::dirty_buffer_mask_lock              | NO      | NO    |
| wait/synch/mutex/aria/TRANSLOG_DESCRIPTOR::file_header_lock                    | NO      | NO    |
| wait/synch/mutex/aria/TRANSLOG_DESCRIPTOR::log_flush_lock                      | NO      | NO    |
| wait/synch/mutex/aria/TRANSLOG_DESCRIPTOR::purger_lock                         | NO      | NO    |
| wait/synch/mutex/aria/TRANSLOG_DESCRIPTOR::sent_to_disk_lock                   | NO      | NO    |
| wait/synch/mutex/aria/TRANSLOG_DESCRIPTOR::unfinished_files_lock               | NO      | NO    |
| wait/synch/mutex/aria/TRN::state_lock                                          | NO      | NO    |
| wait/synch/mutex/csv/tina                                                      | NO      | NO    |
| wait/synch/mutex/csv/TINA_SHARE::mutex                                         | NO      | NO    |
| wait/synch/mutex/innodb/buf_dblwr_mutex                                        | NO      | NO    |
| wait/synch/mutex/innodb/buf_pool_mutex                                         | NO      | NO    |
| wait/synch/mutex/innodb/commit_cond_mutex                                      | NO      | NO    |
| wait/synch/mutex/innodb/dict_foreign_err_mutex                                 | NO      | NO    |
| wait/synch/mutex/innodb/dict_sys_mutex                                         | NO      | NO    |
| wait/synch/mutex/innodb/fil_system_mutex                                       | NO      | NO    |
| wait/synch/mutex/innodb/flush_list_mutex                                       | NO      | NO    |
| wait/synch/mutex/innodb/fts_delete_mutex                                       | NO      | NO    |
| wait/synch/mutex/innodb/fts_doc_id_mutex                                       | NO      | NO    |
| wait/synch/mutex/innodb/ibuf_bitmap_mutex                                      | NO      | NO    |
| wait/synch/mutex/innodb/ibuf_mutex                                             | NO      | NO    |
| wait/synch/mutex/innodb/ibuf_pessimistic_insert_mutex                          | NO      | NO    |
| wait/synch/mutex/innodb/lock_mutex                                             | NO      | NO    |
| wait/synch/mutex/innodb/lock_wait_mutex                                        | NO      | NO    |
| wait/synch/mutex/innodb/log_flush_order_mutex                                  | NO      | NO    |
| wait/synch/mutex/innodb/log_sys_mutex                                          | NO      | NO    |
| wait/synch/mutex/innodb/noredo_rseg_mutex                                      | NO      | NO    |
| wait/synch/mutex/innodb/page_zip_stat_per_index_mutex                          | NO      | NO    |
| wait/synch/mutex/innodb/pending_checkpoint_mutex                               | NO      | NO    |
| wait/synch/mutex/innodb/purge_sys_pq_mutex                                     | NO      | NO    |
| wait/synch/mutex/innodb/recalc_pool_mutex                                      | NO      | NO    |
| wait/synch/mutex/innodb/recv_sys_mutex                                         | NO      | NO    |
| wait/synch/mutex/innodb/redo_rseg_mutex                                        | NO      | NO    |
| wait/synch/mutex/innodb/rtr_active_mutex                                       | NO      | NO    |
| wait/synch/mutex/innodb/rtr_match_mutex                                        | NO      | NO    |
| wait/synch/mutex/innodb/rtr_path_mutex                                         | NO      | NO    |
| wait/synch/mutex/innodb/rw_lock_list_mutex                                     | NO      | NO    |
| wait/synch/mutex/innodb/srv_innodb_monitor_mutex                               | NO      | NO    |
| wait/synch/mutex/innodb/srv_misc_tmpfile_mutex                                 | NO      | NO    |
| wait/synch/mutex/innodb/srv_monitor_file_mutex                                 | NO      | NO    |
| wait/synch/mutex/innodb/srv_threads_mutex                                      | NO      | NO    |
| wait/synch/mutex/innodb/trx_mutex                                              | NO      | NO    |
| wait/synch/mutex/innodb/trx_pool_manager_mutex                                 | NO      | NO    |
| wait/synch/mutex/innodb/trx_pool_mutex                                         | NO      | NO    |
| wait/synch/mutex/innodb/trx_sys_mutex                                          | NO      | NO    |
| wait/synch/mutex/myisam/MI_CHECK::print_msg                                    | NO      | NO    |
| wait/synch/mutex/myisam/MI_SORT_INFO::mutex                                    | NO      | NO    |
| wait/synch/mutex/myisam/MYISAM_SHARE::intern_lock                              | NO      | NO    |
| wait/synch/mutex/myisammrg/MYRG_INFO::mutex                                    | NO      | NO    |
| wait/synch/mutex/mysys/BITMAP::mutex                                           | NO      | NO    |
| wait/synch/mutex/mysys/IO_CACHE::append_buffer_lock                            | NO      | NO    |
| wait/synch/mutex/mysys/IO_CACHE::SHARE_mutex                                   | NO      | NO    |
| wait/synch/mutex/mysys/KEY_CACHE::cache_lock                                   | NO      | NO    |
| wait/synch/mutex/mysys/LOCK_alarm                                              | NO      | NO    |
| wait/synch/mutex/mysys/LOCK_timer                                              | NO      | NO    |
| wait/synch/mutex/mysys/LOCK_uuid_generator                                     | NO      | NO    |
| wait/synch/mutex/mysys/my_thread_var::mutex                                    | NO      | NO    |
| wait/synch/mutex/mysys/THR_LOCK::mutex                                         | NO      | NO    |
| wait/synch/mutex/mysys/THR_LOCK_charset                                        | NO      | NO    |
| wait/synch/mutex/mysys/THR_LOCK_heap                                           | NO      | NO    |
| wait/synch/mutex/mysys/THR_LOCK_lock                                           | NO      | NO    |
| wait/synch/mutex/mysys/THR_LOCK_malloc                                         | NO      | NO    |
| wait/synch/mutex/mysys/THR_LOCK_myisam                                         | NO      | NO    |
| wait/synch/mutex/mysys/THR_LOCK_myisam_mmap                                    | NO      | NO    |
| wait/synch/mutex/mysys/THR_LOCK_net                                            | NO      | NO    |
| wait/synch/mutex/mysys/THR_LOCK_open                                           | NO      | NO    |
| wait/synch/mutex/mysys/THR_LOCK_threads                                        | NO      | NO    |
| wait/synch/mutex/mysys/TMPDIR_mutex                                            | NO      | NO    |
| wait/synch/mutex/partition/Partition_share::auto_inc_mutex                     | NO      | NO    |
| wait/synch/mutex/sql/Ack_receiver::mutex                                       | NO      | NO    |
| wait/synch/mutex/sql/Cversion_lock                                             | NO      | NO    |
| wait/synch/mutex/sql/Delayed_insert::mutex                                     | NO      | NO    |
| wait/synch/mutex/sql/Event_scheduler::LOCK_scheduler_state                     | NO      | NO    |
| wait/synch/mutex/sql/gtid_waiting::LOCK_gtid_waiting                           | NO      | NO    |
| wait/synch/mutex/sql/hash_filo::lock                                           | NO      | NO    |
| wait/synch/mutex/sql/HA_DATA_PARTITION::LOCK_auto_inc                          | NO      | NO    |
| wait/synch/mutex/sql/LOCK_active_mi                                            | NO      | NO    |
| wait/synch/mutex/sql/LOCK_after_binlog_sync                                    | NO      | NO    |
| wait/synch/mutex/sql/LOCK_audit_mask                                           | NO      | NO    |
| wait/synch/mutex/sql/LOCK_binlog                                               | NO      | NO    |
| wait/synch/mutex/sql/LOCK_binlog_state                                         | NO      | NO    |
| wait/synch/mutex/sql/LOCK_commit_ordered                                       | NO      | NO    |
| wait/synch/mutex/sql/LOCK_crypt                                                | NO      | NO    |
| wait/synch/mutex/sql/LOCK_delayed_create                                       | NO      | NO    |
| wait/synch/mutex/sql/LOCK_delayed_insert                                       | NO      | NO    |
| wait/synch/mutex/sql/LOCK_delayed_status                                       | NO      | NO    |
| wait/synch/mutex/sql/LOCK_des_key_file                                         | NO      | NO    |
| wait/synch/mutex/sql/LOCK_error_log                                            | NO      | NO    |
| wait/synch/mutex/sql/LOCK_error_messages                                       | NO      | NO    |
| wait/synch/mutex/sql/LOCK_event_queue                                          | NO      | NO    |
| wait/synch/mutex/sql/LOCK_gdl                                                  | NO      | NO    |
| wait/synch/mutex/sql/LOCK_global_index_stats                                   | NO      | NO    |
| wait/synch/mutex/sql/LOCK_global_system_variables                              | NO      | NO    |
| wait/synch/mutex/sql/LOCK_global_table_stats                                   | NO      | NO    |
| wait/synch/mutex/sql/LOCK_global_user_client_stats                             | NO      | NO    |
| wait/synch/mutex/sql/LOCK_item_func_sleep                                      | NO      | NO    |
| wait/synch/mutex/sql/LOCK_load_client_plugin                                   | NO      | NO    |
| wait/synch/mutex/sql/LOCK_manager                                              | NO      | NO    |
| wait/synch/mutex/sql/LOCK_parallel_entry                                       | NO      | NO    |
| wait/synch/mutex/sql/LOCK_plugin                                               | NO      | NO    |
| wait/synch/mutex/sql/LOCK_prepared_stmt_count                                  | NO      | NO    |
| wait/synch/mutex/sql/LOCK_prepare_ordered                                      | NO      | NO    |
| wait/synch/mutex/sql/LOCK_rpl_semi_sync_master_enabled                         | NO      | NO    |
| wait/synch/mutex/sql/LOCK_rpl_status                                           | NO      | NO    |
| wait/synch/mutex/sql/LOCK_rpl_thread                                           | NO      | NO    |
| wait/synch/mutex/sql/LOCK_rpl_thread_pool                                      | NO      | NO    |
| wait/synch/mutex/sql/LOCK_server_started                                       | NO      | NO    |
| wait/synch/mutex/sql/LOCK_slave_background                                     | NO      | NO    |
| wait/synch/mutex/sql/LOCK_slave_state                                          | NO      | NO    |
| wait/synch/mutex/sql/LOCK_start_thread                                         | NO      | NO    |
| wait/synch/mutex/sql/LOCK_stats                                                | NO      | NO    |
| wait/synch/mutex/sql/LOCK_status                                               | NO      | NO    |
| wait/synch/mutex/sql/LOCK_system_variables_hash                                | NO      | NO    |
| wait/synch/mutex/sql/LOCK_table_cache                                          | NO      | NO    |
| wait/synch/mutex/sql/LOCK_thread_cache                                         | NO      | NO    |
| wait/synch/mutex/sql/LOCK_thread_id                                            | NO      | NO    |
| wait/synch/mutex/sql/LOCK_unused_shares                                        | NO      | NO    |
| wait/synch/mutex/sql/LOCK_user_conn                                            | NO      | NO    |
| wait/synch/mutex/sql/LOCK_uuid_short_generator                                 | NO      | NO    |
| wait/synch/mutex/sql/LOCK_wsrep_cluster_config                                 | NO      | NO    |
| wait/synch/mutex/sql/LOCK_wsrep_config_state                                   | NO      | NO    |
| wait/synch/mutex/sql/LOCK_wsrep_desync                                         | NO      | NO    |
| wait/synch/mutex/sql/LOCK_wsrep_donor_monitor                                  | NO      | NO    |
| wait/synch/mutex/sql/LOCK_wsrep_group_commit                                   | NO      | NO    |
| wait/synch/mutex/sql/LOCK_wsrep_gtid_wait_upto                                 | NO      | NO    |
| wait/synch/mutex/sql/LOCK_wsrep_joiner_monitor                                 | NO      | NO    |
| wait/synch/mutex/sql/LOCK_wsrep_ready                                          | NO      | NO    |
| wait/synch/mutex/sql/LOCK_wsrep_replaying                                      | NO      | NO    |
| wait/synch/mutex/sql/LOCK_wsrep_slave_threads                                  | NO      | NO    |
| wait/synch/mutex/sql/LOCK_wsrep_SR_pool                                        | NO      | NO    |
| wait/synch/mutex/sql/LOCK_wsrep_SR_store                                       | NO      | NO    |
| wait/synch/mutex/sql/LOCK_wsrep_sst                                            | NO      | NO    |
| wait/synch/mutex/sql/LOCK_wsrep_sst_init                                       | NO      | NO    |
| wait/synch/mutex/sql/LOG::LOCK_log                                             | NO      | NO    |
| wait/synch/mutex/sql/Master_info::data_lock                                    | NO      | NO    |
| wait/synch/mutex/sql/Master_info::run_lock                                     | NO      | NO    |
| wait/synch/mutex/sql/Master_info::sleep_lock                                   | NO      | NO    |
| wait/synch/mutex/sql/Master_info::start_stop_lock                              | NO      | NO    |
| wait/synch/mutex/sql/MDL_wait::LOCK_wait_status                                | NO      | NO    |
| wait/synch/mutex/sql/MYSQL_BIN_LOG::LOCK_binlog_background_thread              | NO      | NO    |
| wait/synch/mutex/sql/MYSQL_BIN_LOG::LOCK_binlog_end_pos                        | NO      | NO    |
| wait/synch/mutex/sql/MYSQL_BIN_LOG::LOCK_index                                 | NO      | NO    |
| wait/synch/mutex/sql/MYSQL_BIN_LOG::LOCK_xid_list                              | NO      | NO    |
| wait/synch/mutex/sql/MYSQL_RELAY_LOG::LOCK_binlog_end_pos                      | NO      | NO    |
| wait/synch/mutex/sql/MYSQL_RELAY_LOG::LOCK_index                               | NO      | NO    |
| wait/synch/mutex/sql/PAGE::lock                                                | NO      | NO    |
| wait/synch/mutex/sql/Query_cache::structure_guard_mutex                        | NO      | NO    |
| wait/synch/mutex/sql/Relay_log_info::data_lock                                 | NO      | NO    |
| wait/synch/mutex/sql/Relay_log_info::log_space_lock                            | NO      | NO    |
| wait/synch/mutex/sql/Relay_log_info::run_lock                                  | NO      | NO    |
| wait/synch/mutex/sql/Rpl_group_info::sleep_lock                                | NO      | NO    |
| wait/synch/mutex/sql/Slave_reporting_capability::err_lock                      | NO      | NO    |
| wait/synch/mutex/sql/TABLE_SHARE::LOCK_ha_data                                 | NO      | NO    |
| wait/synch/mutex/sql/TABLE_SHARE::LOCK_rotation                                | NO      | NO    |
| wait/synch/mutex/sql/TABLE_SHARE::LOCK_share                                   | NO      | NO    |
| wait/synch/mutex/sql/TABLE_SHARE::tdc.LOCK_table_share                         | NO      | NO    |
| wait/synch/mutex/sql/TC_LOG_MMAP::LOCK_active                                  | NO      | NO    |
| wait/synch/mutex/sql/TC_LOG_MMAP::LOCK_pending_checkpoint                      | NO      | NO    |
| wait/synch/mutex/sql/TC_LOG_MMAP::LOCK_pool                                    | NO      | NO    |
| wait/synch/mutex/sql/TC_LOG_MMAP::LOCK_sync                                    | NO      | NO    |
| wait/synch/mutex/sql/THD::LOCK_thd_data                                        | NO      | NO    |
| wait/synch/mutex/sql/THD::LOCK_thd_kill                                        | NO      | NO    |
| wait/synch/mutex/sql/THD::LOCK_wakeup_ready                                    | NO      | NO    |
| wait/synch/mutex/sql/tz_LOCK                                                   | NO      | NO    |
| wait/synch/mutex/sql/wait_for_commit::LOCK_wait_commit                         | NO      | NO    |
| wait/synch/mutex/sql/wsrep_sst_thread                                          | NO      | NO    |
| wait/synch/rwlock/aria/KEYINFO::root_lock                                      | NO      | NO    |
| wait/synch/rwlock/aria/SHARE::mmap_lock                                        | NO      | NO    |
| wait/synch/rwlock/aria/TRANSLOG_DESCRIPTOR::open_files_lock                    | NO      | NO    |
| wait/synch/rwlock/myisam/MYISAM_SHARE::key_root_lock                           | NO      | NO    |
| wait/synch/rwlock/myisam/MYISAM_SHARE::mmap_lock                               | NO      | NO    |
| wait/synch/rwlock/mysys/SAFE_HASH::mutex                                       | NO      | NO    |
| wait/synch/rwlock/proxy_proto/rwlock                                           | NO      | NO    |
| wait/synch/rwlock/sql/CRYPTO_dynlock_value::lock                               | NO      | NO    |
| wait/synch/rwlock/sql/LOCK_all_status_vars                                     | NO      | NO    |
| wait/synch/rwlock/sql/LOCK_dboptions                                           | NO      | NO    |
| wait/synch/rwlock/sql/LOCK_grant                                               | NO      | NO    |
| wait/synch/rwlock/sql/LOCK_SEQUENCE                                            | NO      | NO    |
| wait/synch/rwlock/sql/LOCK_ssl_refresh                                         | NO      | NO    |
| wait/synch/rwlock/sql/LOCK_system_variables_hash                               | NO      | NO    |
| wait/synch/rwlock/sql/LOCK_sys_init_connect                                    | NO      | NO    |
| wait/synch/rwlock/sql/LOCK_sys_init_slave                                      | NO      | NO    |
| wait/synch/rwlock/sql/LOGGER::LOCK_logger                                      | NO      | NO    |
| wait/synch/rwlock/sql/MDL_context::LOCK_waiting_for                            | NO      | NO    |
| wait/synch/rwlock/sql/MDL_lock::rwlock                                         | NO      | NO    |
| wait/synch/rwlock/sql/Query_cache_query::lock                                  | NO      | NO    |
| wait/synch/rwlock/sql/TABLE_SHARE::LOCK_stat_serial                            | NO      | NO    |
| wait/synch/rwlock/sql/THD_list::lock                                           | NO      | NO    |
| wait/synch/rwlock/sql/THR_LOCK_servers                                         | NO      | NO    |
| wait/synch/rwlock/sql/THR_LOCK_udf                                             | NO      | NO    |
| wait/synch/rwlock/sql/Vers_field_stats::lock                                   | NO      | NO    |
| wait/synch/sxlock/innodb/btr_search_latch                                      | NO      | NO    |
| wait/synch/sxlock/innodb/dict_operation_lock                                   | NO      | NO    |
| wait/synch/sxlock/innodb/fil_space_latch                                       | NO      | NO    |
| wait/synch/sxlock/innodb/fts_cache_init_rw_lock                                | NO      | NO    |
| wait/synch/sxlock/innodb/fts_cache_rw_lock                                     | NO      | NO    |
| wait/synch/sxlock/innodb/index_online_log                                      | NO      | NO    |
| wait/synch/sxlock/innodb/index_tree_rw_lock                                    | NO      | NO    |
| wait/synch/sxlock/innodb/trx_i_s_cache_lock                                    | NO      | NO    |
| wait/synch/sxlock/innodb/trx_purge_latch                                       | NO      | NO    |
+--------------------------------------------------------------------------------+---------+-------+
996 rows in set (0.005 sec)

1.1.1.2.9.2.1.64 Performance Schema setup_objects Table

Description

The setup_objects table determines whether objects are monitored by the performance schema or not. By default limited to 100 rows, this can be changed by setting the performance_schema_setup_objects_size system variable when the server starts.

It contains the following columns:

ColumnDescription
OBJECT_TYPEType of object to instrument, currently only . Currently, only TABLE', for base table.
OBJECT_SCHEMASchema containing the object, either the literal or % for any schema.
OBJECT_NAMEName of the instrumented object, either the literal or % for any object.
ENABLEDWhether the object's events are instrumented or not. Can be disabled, in which case monitoring is not enabled for those objects.
TIMEDWhether the object's events are timed or not. Can be modified.

When the Performance Schema looks for matches in the setup_objects, there may be more than one row matching, with different ENABLED and TIMED values. It looks for the most specific matches first, that is, it will first look for the specific database and table name combination, then the specific database, only then falling back to a wildcard for both.

Rows can be added or removed from the table, while for existing rows, only the TIMED and ENABLED columns can be updated. By default, all tables except those in the performance_schema, information_schema and mysql databases are instrumented.

1.1.1.2.9.2.1.65 Performance Schema setup_timers Table

Description

The setup_timers table shows the currently selected event timers.

It contains the following columns:

ColumnDescription
NAMEType of instrument the timer is used for.
TIMER_NAMETimer applying to the instrument type. Can be modified.

The TIMER_NAME value can be changed to choose a different timer, and can be any non-NULL value in the performance_timers.TIMER_NAME column.

If you modify the table, monitoring is immediately affected, and currently monitored events would use a combination of old and new timers, which is probably undesirable. It is best to reset the Performance Schema statistics if you make changes to this table.

Example

SELECT * FROM setup_timers;
+-----------+-------------+
| NAME      | TIMER_NAME  |
+-----------+-------------+
| idle      | MICROSECOND |
| wait      | CYCLE       |
| stage     | NANOSECOND  |
| statement | NANOSECOND  |
+-----------+-------------+

1.1.1.2.9.2.1.66 Performance Schema socket_instances Table

The socket_instances table lists active server connections, with each record being a Unix socket file or TCP/IP connection.

The socket_instances table contains the following columns:

ColumnDescription
EVENT_NAMENAME from the setup_instruments table, and the name of the wait/io/socket/* instrument that produced the event.
OBJECT_INSTANCE_BEGINMemory address of the object.
THREAD_IDThread identifier that the server assigns to each socket.
SOCKET_IDThe socket's internal file handle.
IPClient IP address. Blank for Unix socket file, otherwise an IPv4 or IPv6 address. Together with the PORT identifies the connection.
PORTTCP/IP port number, from 0 to 65535. Together with the IP identifies the connection.
STATESocket status, either IDLE if waiting to receive a request from a client, or ACTIVE

1.1.1.2.9.2.1.67 Performance Schema socket_summary_by_event_name Table

It aggregates timer and byte count statistics for all socket I/O operations by socket instrument.

ColumnDescription
EVENT_NAMESocket instrument.
COUNT_STARNumber of summarized events
SUM_TIMER_WAITTotal wait time of the summarized events that are timed.
MIN_TIMER_WAITMinimum wait time of the summarized events that are timed.
AVG_TIMER_WAITAverage wait time of the summarized events that are timed.
MAX_TIMER_WAITMaximum wait time of the summarized events that are timed.
COUNT_READNumber of all read operations, including RECV, RECVFROM, and RECVMSG.
SUM_TIMER_READTotal wait time of all read operations that are timed.
MIN_TIMER_READMinimum wait time of all read operations that are timed.
AVG_TIMER_READAverage wait time of all read operations that are timed.
MAX_TIMER_READMaximum wait time of all read operations that are timed.
SUM_NUMBER_OF_BYTES_READBytes read by read operations.
COUNT_WRITENumber of all write operations, including SEND, SENDTO, and SENDMSG.
SUM_TIMER_WRITETotal wait time of all write operations that are timed.
MIN_TIMER_WRITEMinimum wait time of all write operations that are timed.
AVG_TIMER_WRITEAverage wait time of all write operations that are timed.
MAX_TIMER_WRITEMaximum wait time of all write operations that are timed.
SUM_NUMBER_OF_BYTES_WRITEBytes written by write operations.
COUNT_MISCNumber of all miscellaneous operations not counted above, including CONNECT, LISTEN, ACCEPT, CLOSE, and SHUTDOWN.
SUM_TIMER_MISCTotal wait time of all miscellaneous operations that are timed.
MIN_TIMER_MISCMinimum wait time of all miscellaneous operations that are timed.
AVG_TIMER_MISCAverage wait time of all miscellaneous operations that are timed.
MAX_TIMER_MISCMaximum wait time of all miscellaneous operations that are timed.

You can TRUNCATE the table, which will reset all counters to zero.

Example

SELECT * FROM socket_summary_by_event_name\G
*************************** 1. row ***************************
               EVENT_NAME: wait/io/socket/sql/server_tcpip_socket
               COUNT_STAR: 0
           SUM_TIMER_WAIT: 0
           MIN_TIMER_WAIT: 0
           AVG_TIMER_WAIT: 0
           MAX_TIMER_WAIT: 0
               COUNT_READ: 0
           SUM_TIMER_READ: 0
           MIN_TIMER_READ: 0
           AVG_TIMER_READ: 0
           MAX_TIMER_READ: 0
 SUM_NUMBER_OF_BYTES_READ: 0
              COUNT_WRITE: 0
          SUM_TIMER_WRITE: 0
          MIN_TIMER_WRITE: 0
          AVG_TIMER_WRITE: 0
          MAX_TIMER_WRITE: 0
SUM_NUMBER_OF_BYTES_WRITE: 0
               COUNT_MISC: 0
           SUM_TIMER_MISC: 0
           MIN_TIMER_MISC: 0
           AVG_TIMER_MISC: 0
           MAX_TIMER_MISC: 0
*************************** 2. row ***************************
               EVENT_NAME: wait/io/socket/sql/server_unix_socket
               COUNT_STAR: 0
           SUM_TIMER_WAIT: 0
           MIN_TIMER_WAIT: 0
           AVG_TIMER_WAIT: 0
           MAX_TIMER_WAIT: 0
               COUNT_READ: 0
           SUM_TIMER_READ: 0
           MIN_TIMER_READ: 0
           AVG_TIMER_READ: 0
           MAX_TIMER_READ: 0
 SUM_NUMBER_OF_BYTES_READ: 0
              COUNT_WRITE: 0
          SUM_TIMER_WRITE: 0
          MIN_TIMER_WRITE: 0
          AVG_TIMER_WRITE: 0
          MAX_TIMER_WRITE: 0
SUM_NUMBER_OF_BYTES_WRITE: 0
               COUNT_MISC: 0
           SUM_TIMER_MISC: 0
           MIN_TIMER_MISC: 0
           AVG_TIMER_MISC: 0
           MAX_TIMER_MISC: 0
...

1.1.1.2.9.2.1.68 Performance Schema socket_summary_by_instance Table

It aggregates timer and byte count statistics for all socket I/O operations by socket instance.

ColumnDescription
EVENT_NAMESocket instrument.
OBJECT_INSTANCE_BEGINAddress in memory.
COUNT_STARNumber of summarized events
SUM_TIMER_WAITTotal wait time of the summarized events that are timed.
MIN_TIMER_WAITMinimum wait time of the summarized events that are timed.
AVG_TIMER_WAITAverage wait time of the summarized events that are timed.
MAX_TIMER_WAITMaximum wait time of the summarized events that are timed.
COUNT_READNumber of all read operations, including RECV, RECVFROM, and RECVMSG.
SUM_TIMER_READTotal wait time of all read operations that are timed.
MIN_TIMER_READMinimum wait time of all read operations that are timed.
AVG_TIMER_READAverage wait time of all read operations that are timed.
MAX_TIMER_READMaximum wait time of all read operations that are timed.
SUM_NUMBER_OF_BYTES_READBytes read by read operations.
COUNT_WRITENumber of all write operations, including SEND, SENDTO, and SENDMSG.
SUM_TIMER_WRITETotal wait time of all write operations that are timed.
MIN_TIMER_WRITEMinimum wait time of all write operations that are timed.
AVG_TIMER_WRITEAverage wait time of all write operations that are timed.
MAX_TIMER_WRITEMaximum wait time of all write operations that are timed.
SUM_NUMBER_OF_BYTES_WRITEBytes written by write operations.
COUNT_MISCNumber of all miscellaneous operations not counted above, including CONNECT, LISTEN, ACCEPT, CLOSE, and SHUTDOWN.
SUM_TIMER_MISCTotal wait time of all miscellaneous operations that are timed.
MIN_TIMER_MISCMinimum wait time of all miscellaneous operations that are timed.
AVG_TIMER_MISCAverage wait time of all miscellaneous operations that are timed.
MAX_TIMER_MISCMaximum wait time of all miscellaneous operations that are timed.

The corresponding row in the table is deleted when a connection terminates.

You can TRUNCATE the table, which will reset all counters to zero.

1.1.1.2.9.2.1.69 Performance Schema status_by_thread Table

MariaDB starting with 10.5.2

The session_status table was added in MariaDB 10.5.2.

The status_by_thread table contains status variable information about active foreground threads. The table does not collect statistics for Com_xxx variables.

The table contains the following columns:

ColumnDescription
THREAD_IDThe thread identifier of the session in which the status variable is defined.
VARIABLE_NAMEStatus variable name.
VARIABLE_VALUEAggregated status variable value.

If TRUNCATE TABLE is run, will aggregate the status for all threads to the global status and account status, then reset the thread status. If account statistics are not collected but host and user status are, the session status is added to host and user status.

1.1.1.2.9.2.1.70 Performance Schema table_io_waits_summary_by_index_usage Table

The table_io_waits_summary_by_index_usage table records table I/O waits by index.

ColumnDescription
OBJECT_TYPETABLE in the case of all indexes.
OBJECT_SCHEMASchema name.
OBJECT_NAMETable name.
INDEX_NAMEIndex name, or PRIMARY for the primary index, NULL for no index (inserts are counted in this case).
COUNT_STARNumber of summarized events and the sum of the x_READ and x_WRITE columns.
SUM_TIMER_WAITTotal wait time of the summarized events that are timed.
MIN_TIMER_WAITMinimum wait time of the summarized events that are timed.
AVG_TIMER_WAITAverage wait time of the summarized events that are timed.
MAX_TIMER_WAITMaximum wait time of the summarized events that are timed.
COUNT_READNumber of all read operations, and the sum of the equivalent x_FETCH columns.
SUM_TIMER_READTotal wait time of all read operations that are timed.
MIN_TIMER_READMinimum wait time of all read operations that are timed.
AVG_TIMER_READAverage wait time of all read operations that are timed.
MAX_TIMER_READMaximum wait time of all read operations that are timed.
COUNT_WRITENumber of all write operations, and the sum of the equivalent x_INSERT, x_UPDATE and x_DELETE columns.
SUM_TIMER_WRITETotal wait time of all write operations that are timed.
MIN_TIMER_WRITEMinimum wait time of all write operations that are timed.
AVG_TIMER_WRITEAverage wait time of all write operations that are timed.
MAX_TIMER_WRITEMaximum wait time of all write operations that are timed.
COUNT_FETCHNumber of all fetch operations.
SUM_TIMER_FETCHTotal wait time of all fetch operations that are timed.
MIN_TIMER_FETCHMinimum wait time of all fetch operations that are timed.
AVG_TIMER_FETCHAverage wait time of all fetch operations that are timed.
MAX_TIMER_FETCHMaximum wait time of all fetch operations that are timed.
COUNT_INSERTNumber of all insert operations.
SUM_TIMER_INSERTTotal wait time of all insert operations that are timed.
MIN_TIMER_INSERTMinimum wait time of all insert operations that are timed.
AVG_TIMER_INSERTAverage wait time of all insert operations that are timed.
MAX_TIMER_INSERTMaximum wait time of all insert operations that are timed.
COUNT_UPDATENumber of all update operations.
SUM_TIMER_UPDATETotal wait time of all update operations that are timed.
MIN_TIMER_UPDATEMinimum wait time of all update operations that are timed.
AVG_TIMER_UPDATEAverage wait time of all update operations that are timed.
MAX_TIMER_UPDATEMaximum wait time of all update operations that are timed.
COUNT_DELETENumber of all delete operations.
SUM_TIMER_DELETETotal wait time of all delete operations that are timed.
MIN_TIMER_DELETEMinimum wait time of all delete operations that are timed.
AVG_TIMER_DELETEAverage wait time of all delete operations that are timed.
MAX_TIMER_DELETEMaximum wait time of all delete operations that are timed.

You can TRUNCATE the table, which will reset all counters to zero. The table is also truncated if the table_io_waits_summary_by_table table is truncated.

If a table's index structure is changed, index statistics recorded in this table may also be reset.

1.1.1.2.9.2.1.71 Performance Schema table_io_waits_summary_by_table Table

The table_io_waits_summary_by_table table records table I/O waits by table.

ColumnDescription
OBJECT_TYPESince this table records waits by table, always set to TABLE.
OBJECT_SCHEMASchema name.
OBJECT_NAMETable name.
COUNT_STARNumber of summarized events and the sum of the x_READ and x_WRITE columns.
SUM_TIMER_WAITTotal wait time of the summarized events that are timed.
MIN_TIMER_WAITMinimum wait time of the summarized events that are timed.
AVG_TIMER_WAITAverage wait time of the summarized events that are timed.
MAX_TIMER_WAITMaximum wait time of the summarized events that are timed.
COUNT_READNumber of all read operations, and the sum of the equivalent x_FETCH columns.
SUM_TIMER_READTotal wait time of all read operations that are timed.
MIN_TIMER_READMinimum wait time of all read operations that are timed.
AVG_TIMER_READAverage wait time of all read operations that are timed.
MAX_TIMER_READMaximum wait time of all read operations that are timed.
COUNT_WRITENumber of all write operations, and the sum of the equivalent x_INSERT, x_UPDATE and x_DELETE columns.
SUM_TIMER_WRITETotal wait time of all write operations that are timed.
MIN_TIMER_WRITEMinimum wait time of all write operations that are timed.
AVG_TIMER_WRITEAverage wait time of all write operations that are timed.
MAX_TIMER_WRITEMaximum wait time of all write operations that are timed.
COUNT_FETCHNumber of all fetch operations.
SUM_TIMER_FETCHTotal wait time of all fetch operations that are timed.
MIN_TIMER_FETCHMinimum wait time of all fetch operations that are timed.
AVG_TIMER_FETCHAverage wait time of all fetch operations that are timed.
MAX_TIMER_FETCHMaximum wait time of all fetch operations that are timed.
COUNT_INSERTNumber of all insert operations.
SUM_TIMER_INSERTTotal wait time of all insert operations that are timed.
MIN_TIMER_INSERTMinimum wait time of all insert operations that are timed.
AVG_TIMER_INSERTAverage wait time of all insert operations that are timed.
MAX_TIMER_INSERTMaximum wait time of all insert operations that are timed.
COUNT_UPDATENumber of all update operations.
SUM_TIMER_UPDATETotal wait time of all update operations that are timed.
MIN_TIMER_UPDATEMinimum wait time of all update operations that are timed.
AVG_TIMER_UPDATEAverage wait time of all update operations that are timed.
MAX_TIMER_UPDATEMaximum wait time of all update operations that are timed.
COUNT_DELETENumber of all delete operations.
SUM_TIMER_DELETETotal wait time of all delete operations that are timed.
MIN_TIMER_DELETEMinimum wait time of all delete operations that are timed.
AVG_TIMER_DELETEAverage wait time of all delete operations that are timed.
MAX_TIMER_DELETEMaximum wait time of all delete operations that are timed.

You can TRUNCATE the table, which will reset all counters to zero. Truncating this table will also truncate the table_io_waits_summary_by_index_usage table.

1.1.1.2.9.2.1.72 Performance Schema table_lock_waits_summary_by_table Table

The table_lock_waits_summary_by_table table records table lock waits by table.

ColumnDescription
OBJECT_TYPESince this table records waits by table, always set to TABLE.
OBJECT_SCHEMASchema name.
OBJECT_NAMETable name.
COUNT_STARNumber of summarized events and the sum of the x_READ and x_WRITE columns.
SUM_TIMER_WAITTotal wait time of the summarized events that are timed.
MIN_TIMER_WAITMinimum wait time of the summarized events that are timed.
AVG_TIMER_WAITAverage wait time of the summarized events that are timed.
MAX_TIMER_WAITMaximum wait time of the summarized events that are timed.
COUNT_READNumber of all read operations, and the sum of the equivalent x_READ_NORMAL, x_READ_WITH_SHARED_LOCKS, x_READ_HIGH_PRIORITY and x_READ_NO_INSERT columns.
SUM_TIMER_READTotal wait time of all read operations that are timed.
MIN_TIMER_READMinimum wait time of all read operations that are timed.
AVG_TIMER_READAverage wait time of all read operations that are timed.
MAX_TIMER_READMaximum wait time of all read operations that are timed.
COUNT_WRITENumber of all write operations, and the sum of the equivalent x_WRITE_ALLOW_WRITE, x_WRITE_CONCURRENT_INSERT, x_WRITE_DELAYED, x_WRITE_LOW_PRIORITY and x_WRITE_NORMAL columns.
SUM_TIMER_WRITETotal wait time of all write operations that are timed.
MIN_TIMER_WRITEMinimum wait time of all write operations that are timed.
AVG_TIMER_WRITEAverage wait time of all write operations that are timed.
MAX_TIMER_WRITEMaximum wait time of all write operations that are timed.
COUNT_READ_NORMALNumber of all internal read normal locks.
SUM_TIMER_READ_NORMALTotal wait time of all internal read normal locks that are timed.
MIN_TIMER_READ_NORMALMinimum wait time of all internal read normal locks that are timed.
AVG_TIMER_READ_NORMALAverage wait time of all internal read normal locks that are timed.
MAX_TIMER_READ_NORMALMaximum wait time of all internal read normal locks that are timed.
COUNT_READ_WITH_SHARED_LOCKSNumber of all internal read with shared locks.
SUM_TIMER_READ_WITH_SHARED_LOCKSTotal wait time of all internal read with shared locks that are timed.
MIN_TIMER_READ_WITH_SHARED_LOCKSMinimum wait time of all internal read with shared locks that are timed.
AVG_TIMER_READ_WITH_SHARED_LOCKSAverage wait time of all internal read with shared locks that are timed.
MAX_TIMER_READ_WITH_SHARED_LOCKSMaximum wait time of all internal read with shared locks that are timed.
COUNT_READ_HIGH_PRIORITYNumber of all internal read high priority locks.
SUM_TIMER_READ_HIGH_PRIORITYTotal wait time of all internal read high priority locks that are timed.
MIN_TIMER_READ_HIGH_PRIORITYMinimum wait time of all internal read high priority locks that are timed.
AVG_TIMER_READ_HIGH_PRIORITYAverage wait time of all internal read high priority locks that are timed.
MAX_TIMER_READ_HIGH_PRIORITYMaximum wait time of all internal read high priority locks that are timed.
COUNT_READ_NO_INSERTNumber of all internal read no insert locks.
SUM_TIMER_READ_NO_INSERTTotal wait time of all internal read no insert locks that are timed.
MIN_TIMER_READ_NO_INSERTMinimum wait time of all internal read no insert locks that are timed.
AVG_TIMER_READ_NO_INSERTAverage wait time of all internal read no insert locks that are timed.
MAX_TIMER_READ_NO_INSERTMaximum wait time of all internal read no insert locks that are timed.
COUNT_READ_EXTERNALNumber of all external read locks.
SUM_TIMER_READ_EXTERNALTotal wait time of all external read locks that are timed.
MIN_TIMER_READ_EXTERNALMinimum wait time of all external read locks that are timed.
AVG_TIMER_READ_EXTERNALAverage wait time of all external read locks that are timed.
MAX_TIMER_READ_EXTERNALMaximum wait time of all external read locks that are timed.
COUNT_WRITE_ALLOW_WRITENumber of all internal read normal locks.
SUM_TIMER_WRITE_ALLOW_WRITETotal wait time of all internal write allow write locks that are timed.
MIN_TIMER_WRITE_ALLOW_WRITEMinimum wait time of all internal write allow write locks that are timed.
AVG_TIMER_WRITE_ALLOW_WRITEAverage wait time of all internal write allow write locks that are timed.
MAX_TIMER_WRITE_ALLOW_WRITEMaximum wait time of all internal write allow write locks that are timed.
COUNT_WRITE_CONCURRENT_INSERTNumber of all internal concurrent insert write locks.
SUM_TIMER_WRITE_CONCURRENT_INSERTTotal wait time of all internal concurrent insert write locks that are timed.
MIN_TIMER_WRITE_CONCURRENT_INSERTMinimum wait time of all internal concurrent insert write locks that are timed.
AVG_TIMER_WRITE_CONCURRENT_INSERTAverage wait time of all internal concurrent insert write locks that are timed.
MAX_TIMER_WRITE_CONCURRENT_INSERTMaximum wait time of all internal concurrent insert write locks that are timed.
COUNT_WRITE_DELAYEDNumber of all internal write delayed locks.
SUM_TIMER_WRITE_DELAYEDTotal wait time of all internal write delayed locks that are timed.
MIN_TIMER_WRITE_DELAYEDMinimum wait time of all internal write delayed locks that are timed.
AVG_TIMER_WRITE_DELAYEDAverage wait time of all internal write delayed locks that are timed.
MAX_TIMER_WRITE_DELAYEDMaximum wait time of all internal write delayed locks that are timed.
COUNT_WRITE_LOW_PRIORITYNumber of all internal write low priority locks.
SUM_TIMER_WRITE_LOW_PRIORITYTotal wait time of all internal write low priority locks that are timed.
MIN_TIMER_WRITE_LOW_PRIORITYMinimum wait time of all internal write low priority locks that are timed.
AVG_TIMER_WRITE_LOW_PRIORITYAverage wait time of all internal write low priority locks that are timed.
MAX_TIMER_WRITE_LOW_PRIORITYMaximum wait time of all internal write low priority locks that are timed.
COUNT_WRITE_NORMALNumber of all internal write normal locks.
SUM_TIMER_WRITE_NORMALTotal wait time of all internal write normal locks that are timed.
MIN_TIMER_WRITE_NORMALMinimum wait time of all internal write normal locks that are timed.
AVG_TIMER_WRITE_NORMALAverage wait time of all internal write normal locks that are timed.
MAX_TIMER_WRITE_NORMALMaximum wait time of all internal write normal locks that are timed.
COUNT_WRITE_EXTERNALNumber of all external write locks.
SUM_TIMER_WRITE_EXTERNALTotal wait time of all external write locks that are timed.
MIN_TIMER_WRITE_EXTERNALMinimum wait time of all external write locks that are timed.
AVG_TIMER_WRITE_EXTERNALAverage wait time of all external write locks that are timed.
MAX_TIMER_WRITE_EXTERNALMaximum wait time of all external write locks that are timed.

You can TRUNCATE the table, which will reset all counters to zero.

1.1.1.2.9.2.1.73 Performance Schema threads Table

Each server thread is represented as a row in the threads table.

The threads table contains the following columns:

ColumnDescription
THREAD_IDA unique thread identifier.
NAMEName associated with the server's thread instrumentation code, for example thread/sql/main for the server's main() function, and thread/sql/one_connection for a user connection.
TYPEFOREGROUND or BACKGROUND, depending on the thread type. User connection threads are FOREGROUND, internal server threads are BACKGROUND.
PROCESSLIST_IDThe PROCESSLIST.ID value for threads displayed in the INFORMATION_SCHEMA.PROCESSLIST table, or 0 for background threads. Also corresponds with the CONNECTION_ID() return value for the thread.
PROCESSLIST_USERForeground thread user, or NULL for a background thread.
PROCESSLIST_HOSTForeground thread host, or NULL for a background thread.
PROCESSLIST_DBThread's default database, or NULL if none exists.
PROCESSLIST_COMMANDType of command executed by the thread. These correspond to the the COM_xxx client/server protocol commands, and the Com_xxx status variables. See Thread Command Values.
PROCESSLIST_TIMETime in seconds the thread has been in its current state.
PROCESSLIST_STATEAction, event or state indicating what the thread is doing.
PROCESSLIST_INFOStatement being executed by the thread, or NULL if a statement is not being executed. If a statement results in calling other statements, such as for a stored procedure, the innermost statement from the stored procedure is shown here.
PARENT_THREAD_IDTHREAD_ID of the parent thread, if any. Subthreads can for example be spawned as a result of INSERT DELAYED statements.
ROLEUnused.
INSTRUMENTEDYES or NO for Whether the thread is instrumented or not. For foreground threads, the initial value is determined by whether there's a user/host match in the setup_actors table. Subthreads are again matched, while for background threads, this will be set to YES by default. To monitor events that the thread executes, INSTRUMENTED must be YES and the thread_instrumentation consumer in the setup_consumers table must also be YES.
HISTORYYES or NO for Whether to log historical events for the thread. For foreground threads, the initial value is determined by whether there's a user/host match in the setup_actors table. Subthreads are again matched, while for background threads, this will be set to YES by default. To monitor events that the thread executes, INSTRUMENTED must be YES and the thread_instrumentation consumer in the setup_consumers table must also be YES. Added in MariaDB 10.5.
CONNECTION_TYPEThe protocol used to establish the connection, or NULL for background threads. Added in MariaDB 10.5.
THREAD_OS_IDThe thread or task identifier as defined by the underlying operating system, if there is one. Added in MariaDB 10.5

Example

SELECT * FROM performance_schema.threads\G;
*************************** 1. row ***************************
          THREAD_ID: 1
               NAME: thread/sql/main
               TYPE: BACKGROUND
     PROCESSLIST_ID: NULL
   PROCESSLIST_USER: NULL
   PROCESSLIST_HOST: NULL
     PROCESSLIST_DB: NULL
PROCESSLIST_COMMAND: NULL
   PROCESSLIST_TIME: 215859
  PROCESSLIST_STATE: Table lock
   PROCESSLIST_INFO: INTERNAL DDL LOG RECOVER IN PROGRESS
   PARENT_THREAD_ID: NULL
               ROLE: NULL
       INSTRUMENTED: YES
...
*************************** 21. row ***************************
          THREAD_ID: 64
               NAME: thread/sql/one_connection
               TYPE: FOREGROUND
     PROCESSLIST_ID: 44
   PROCESSLIST_USER: root
   PROCESSLIST_HOST: localhost
     PROCESSLIST_DB: NULL
PROCESSLIST_COMMAND: Query
   PROCESSLIST_TIME: 0
  PROCESSLIST_STATE: Sending data
   PROCESSLIST_INFO: SELECT * FROM performance_schema.threads
   PARENT_THREAD_ID: NULL
               ROLE: NULL
       INSTRUMENTED: YES

1.1.1.2.9.2.1.74 Performance Schema users Table

Description

Each user that connects to the server is stored as a row in the users table, along with current and total connections.

The table size is determined at startup by the value of the performance_schema_users_size system variable. If this is set to 0, user statistics will be disabled.

ColumnDescription
USERThe connection's client user name for the connection, or NULL if an internal thread.
CURRENT_CONNECTIONSCurrent connections for the user.
TOTAL_CONNECTIONSTotal connections for the user.

Example

SELECT * FROM performance_schema.users;
+------------------+---------------------+-------------------+
| USER             | CURRENT_CONNECTIONS | TOTAL_CONNECTIONS |
+------------------+---------------------+-------------------+
| debian-sys-maint |                   0 |                35 |
| NULL             |                  20 |                23 |
| root             |                   1 |                 2 |
+------------------+---------------------+-------------------+

1.1.1.2.9.2.2 Performance Schema Overview

Contents

  1. Introduction
  2. Activating the Performance Schema
  3. Enabling the Performance Schema
  4. Listing Performance Schema Variables
  5. Column Comments
  6. See Also

The Performance Schema is a feature for monitoring server performance.


Introduction

It is implemented as a storage engine, and so will appear in the list of storage engines available.

SHOW ENGINES;
+--------------------+---------+----------------------------------+--------------+------+------------+
| Engine             | Support | Comment                          | Transactions | XA   | Savepoints |
+--------------------+---------+----------------------------------+--------------+------+------------+
| ...                |         |                                  |              |      |            |
| PERFORMANCE_SCHEMA | YES     | Performance Schema               | NO           | NO   | NO         |
| ...                |         |                                  |              |      |            |
+--------------------+---------+----------------------------------+--------------+------+------------+

However, performance_schema is not a regular storage engine for storing data, it's a mechanism for implementing the Performance Schema feature.

The storage engine contains a database called performance_schema, which in turn consists of a number of tables that can be queried with regular SQL statements, returning specific performance information.

USE performance_schema

SHOW TABLES;
+----------------------------------------------------+
| Tables_in_performance_schema                       |
+----------------------------------------------------+
| accounts                                           |
...
| users                                              |
+----------------------------------------------------+
80 rows in set (0.00 sec)

See List of Performance Schema Tables for a full list and links to detailed descriptions of each table. From MariaDB 10.5, there are 80 Performance Schema tables, while until MariaDB 10.4, there are 52.

Activating the Performance Schema

The performance schema is disabled by default for performance reasons. You can check its current status by looking at the value of the performance_schema system variable.

SHOW VARIABLES LIKE 'performance_schema';
+--------------------+-------+
| Variable_name      | Value |
+--------------------+-------+
| performance_schema | ON    |
+--------------------+-------+

The performance schema cannot be activated at runtime - it must be set when the server starts by adding the following line in your my.cnf configuration file.

performance_schema=ON

Until MariaDB 10.4, all memory used by the Performance Schema is allocated at startup. From MariaDB 10.5, some memory is allocated dynamically, depending on load, number of connections, number of tables open etc.

Enabling the Performance Schema

You need to set up all consumers (starting collection of data) and instrumentations (what to collect):

UPDATE performance_schema.setup_consumers SET ENABLED = 'YES';
UPDATE performance_schema.setup_instruments SET ENABLED = 'YES', TIMED = 'YES';

You can decide what to enable/disable with WHERE NAME like "%what_to_enable"; You can disable instrumentations by setting ENABLED to "NO".

You can also do this in your my.cnf file. The following enables all instrumentation of all stages (computation units) in MariaDB:

[mysqld]
performance_schema=ON
performance-schema-instrument='stage/%=ON'
performance-schema-consumer-events-stages-current=ON
performance-schema-consumer-events-stages-history=ON
performance-schema-consumer-events-stages-history-long=ON

Listing Performance Schema Variables

SHOW VARIABLES LIKE "perf%";
+--------------------------------------------------------+-------+
| Variable_name                                          | Value |
+--------------------------------------------------------+-------+
| performance_schema                                     | ON    |
...
| performance_schema_users_size                          | 100   |
+--------------------------------------------------------+-------+

See Performance Schema System Variables for a full list of available system variables.

Note that the "consumer" events are not shown on this list, as they are only available as options, not as system variables, and they can only be enabled at startup.

Column Comments

MariaDB starting with 10.7.1

From MariaDB 10.7.1, comments have been added to table columns in the Performance Schema. These can be viewed with, for example:

SELECT column_name, column_comment FROM information_schema.columns 
  WHERE table_schema='performance_schema' AND table_name='file_instances';
...
*************************** 2. row ***************************
   column_name: EVENT_NAME
column_comment: Instrument name associated with the file.
*************************** 3. row ***************************
   column_name: OPEN_COUNT
column_comment: Open handles on the file. A value of greater than zero means 
                that the file is currently open.
...

See Also

1.1.1.2.9.2.3 Performance Schema Status Variables

Contents

  1. Performance_schema_accounts_lost
  2. Performance_schema_cond_classes_lost
  3. Performance_schema_cond_instances_lost
  4. Performance_schema_digest_lost
  5. Performance_schema_file_classes_lost
  6. Performance_schema_file_handles_lost
  7. Performance_schema_file_instances_lost
  8. Performance_schema_hosts_lost
  9. Performance_schema_index_stat_lost
  10. Performance_schema_locker_lost
  11. Performance_schema_memory_classes_lost
  12. Performance_schema_metadata_lock_lost
  13. Performance_schema_mutex_classes_lost
  14. Performance_schema_mutex_instances_lost
  15. Performance_schema_nested_statement_lost
  16. Performance_schema_prepared_statements_lost
  17. Performance_schema_program_lost
  18. Performance_schema_rwlock_classes_lost
  19. Performance_schema_rwlock_instances_lost
  20. Performance_schema_session_connect_attrs_lost
  21. Performance_schema_socket_classes_lost
  22. Performance_schema_socket_instances_lost
  23. Performance_schema_stage_classes_lost
  24. Performance_schema_statement_classes_lost
  25. Performance_schema_table_handles_lost
  26. Performance_schema_table_instances_lost
  27. Performance_schema_table_lock_stat_lost
  28. Performance_schema_thread_classes_lost
  29. Performance_schema_thread_instances_lost
  30. Performance_schema_users_lost

This page documents status variables related to the Performance Schema. See Server Status Variables for a complete list of status variables that can be viewed with SHOW STATUS.

See also the Full list of MariaDB options, system and status variables.

Performance_schema_accounts_lost

  • Description: Number of times a row could not be added to the performance schema accounts table due to it being full. The global value can be flushed by FLUSH STATUS.
  • Scope: Global, Session
  • Data Type: numeric

Performance_schema_cond_classes_lost

  • Description: Number of condition instruments that could not be loaded.
  • Scope: Global, Session
  • Data Type: numeric

Performance_schema_cond_instances_lost

  • Description: Number of instances a condition object could not be created. The global value can be flushed by FLUSH STATUS.
  • Scope: Global, Session
  • Data Type: numeric

Performance_schema_digest_lost

  • Description: The global value can be flushed by FLUSH STATUS.
  • Scope: Global, Session
  • Data Type: numeric

Performance_schema_file_classes_lost

  • Description: Number of file instruments that could not be loaded.
  • Scope: Global, Session
  • Data Type: numeric

Performance_schema_file_handles_lost

  • Description: Number of instances a file object could not be opened. The global value can be flushed by FLUSH STATUS.
  • Scope: Global, Session
  • Data Type: numeric

Performance_schema_file_instances_lost

  • Description: Number of instances a file object could not be created. The global value can be flushed by FLUSH STATUS.
  • Scope: Global, Session
  • Data Type: numeric

Performance_schema_hosts_lost

  • Description: Number of times a row could not be added to the performance schema hosts table due to it being full. The global value can be flushed by FLUSH STATUS.
  • Scope: Global, Session
  • Data Type: numeric

Performance_schema_index_stat_lost

  • Description:
  • Scope: Global, Session
  • Data Type: numeric
  • Introduced: MariaDB 10.5.2

Performance_schema_locker_lost

  • Description: Number of events not recorded, due to either being recursive, or having a deeper nested events stack than the implementation limit. The global value can be flushed by FLUSH STATUS.
  • Scope: Global, Session
  • Data Type: numeric

Performance_schema_memory_classes_lost

  • Description:
  • Scope: Global, Session
  • Data Type: numeric
  • Introduced: MariaDB 10.5.2

Performance_schema_metadata_lock_lost

  • Description:
  • Scope: Global, Session
  • Data Type: numeric
  • Introduced: MariaDB 10.5.2

Performance_schema_mutex_classes_lost

  • Description: Number of mutual exclusion instruments that could not be loaded.
  • Scope: Global, Session
  • Data Type: numeric

Performance_schema_mutex_instances_lost

  • Description: Number of instances a mutual exclusion object could not be created. The global value can be flushed by FLUSH STATUS.
  • Scope: Global, Session
  • Data Type: numeric

Performance_schema_nested_statement_lost

  • Description:
  • Scope: Global, Session
  • Data Type: numeric
  • Introduced: MariaDB 10.5.2

Performance_schema_prepared_statements_lost

  • Description:
  • Scope: Global, Session
  • Data Type: numeric
  • Introduced: MariaDB 10.5.2

Performance_schema_program_lost

  • Description:
  • Scope: Global, Session
  • Data Type: numeric
  • Introduced: MariaDB 10.5.2

Performance_schema_rwlock_classes_lost

  • Description: Number of read/write lock instruments that could not be loaded.
  • Scope: Global, Session
  • Data Type: numeric

Performance_schema_rwlock_instances_lost

  • Description: Number of instances a read/write lock object could not be created. The global value can be flushed by FLUSH STATUS.
  • Scope: Global, Session
  • Data Type: numeric

Performance_schema_session_connect_attrs_lost

  • Description: Number of connections for which connection attribute truncation has occurred. The global value can be flushed by FLUSH STATUS.
  • Scope: Global, Session
  • Data Type: numeric

Performance_schema_socket_classes_lost

  • Description:
  • Scope: Global, Session
  • Data Type: numeric

Performance_schema_socket_instances_lost

  • Description: Number of instances a socket object could not be created. The global value can be flushed by FLUSH STATUS.
  • Scope: Global, Session
  • Data Type: numeric

Performance_schema_stage_classes_lost

  • Description: Number of stage event instruments that could not be loaded. The global value can be flushed by FLUSH STATUS.
  • Scope: Global, Session
  • Data Type: numeric

Performance_schema_statement_classes_lost

  • Description: Number of statement instruments that could not be loaded. The global value can be flushed by FLUSH STATUS.
  • Scope: Global, Session
  • Data Type: numeric

Performance_schema_table_handles_lost

  • Description: Number of instances a table object could not be opened. The global value can be flushed by FLUSH STATUS.
  • Scope: Global, Session
  • Data Type: numeric

Performance_schema_table_instances_lost

  • Description: Number of instances a table object could not be created. The global value can be flushed by FLUSH STATUS.
  • Scope: Global, Session
  • Data Type: numeric

Performance_schema_table_lock_stat_lost

  • Description:
  • Scope: Global, Session
  • Data Type: numeric
  • Introduced: MariaDB 10.5.2

Performance_schema_thread_classes_lost

  • Description: Number of thread instruments that could not be loaded.
  • Scope: Global, Session
  • Data Type: numeric

Performance_schema_thread_instances_lost

  • Description: Number of instances thread object could not be created. The global value can be flushed by FLUSH STATUS.
  • Scope: Global, Session
  • Data Type: numeric

Performance_schema_users_lost

  • Description: Number of times a row could not be added to the performance schema users table due to it being full. The global value can be flushed by FLUSH STATUS.
  • Scope: Global, Session
  • Data Type: numeric

1.1.1.2.9.2.4 Performance Schema System Variables

Contents

  1. performance_schema
  2. performance_schema_accounts_size
  3. performance_schema_digests_size
  4. performance_schema_events_stages_history_long_size
  5. performance_schema_events_stages_history_size
  6. performance_schema_events_statements_history_long_size
  7. performance_schema_events_statements_history_size
  8. performance_schema_events_transactions_history_long_size
  9. performance_schema_events_transactions_history_size
  10. performance_schema_events_waits_history_long_size
  11. performance_schema_events_waits_history_size
  12. performance_schema_hosts_size
  13. performance_schema_max_cond_classes
  14. performance_schema_max_cond_instances
  15. performance_schema_max_digest_length
  16. performance_schema_max_file_classes
  17. performance_schema_max_file_handles
  18. performance_schema_max_file_instances
  19. performance_schema_max_index_stat
  20. performance_schema_max_memory_classes
  21. performance_schema_max_metadata_locks
  22. performance_schema_max_mutex_classes
  23. performance_schema_max_mutex_instances
  24. performance_schema_max_prepared_statement_instances
  25. performance_schema_max_program_instances
  26. performance_schema_max_rwlock_classes
  27. performance_schema_max_rwlock_instances
  28. performance_schema_max_socket_classes
  29. performance_schema_max_socket_instances
  30. performance_schema_max_sql_text_length
  31. performance_schema_max_stage_classes
  32. performance_schema_max_statement_classes
  33. performance_schema_max_statement_stack
  34. performance_schema_max_table_handles
  35. performance_schema_max_table_instances
  36. performance_schema_max_table_lock_stat
  37. performance_schema_max_thread_classes
  38. performance_schema_max_thread_instances
  39. performance_schema_session_connect_attrs_size
  40. performance_schema_setup_actors_size
  41. performance_schema_setup_objects_size
  42. performance_schema_users_size

The following variables are used with MariaDB's Performance Schema. See Performance Schema Options for Performance Schema options that are not system variables. See Server System Variables for a complete list of system variables and instructions on setting them.

See also the Full list of MariaDB options, system and status variables.

performance_schema

  • Description: If set to 1 (0 is default), enables the Performance Schema
  • Commandline: --performance-schema=#
  • Scope: Global
  • Dynamic: No
  • Data Type: boolean
  • Default Value: OFF

performance_schema_accounts_size

  • Description: Maximum number of rows in the performance_schema.accounts table. If set to 0, the Performance Schema will not store statistics in the accounts table. Use -1 (the default) for automated sizing.
  • Commandline: --performance-schema-accounts-size=#
  • Scope: Global
  • Dynamic: No
  • Data Type: numeric
  • Default Value: -1
  • Range: -1 to 1048576

performance_schema_digests_size

  • Description: Maximum number of rows that can be stored in the events_statements_summary_by_digest table. 0 for disabling, -1 (the default) for automated sizing.
  • Commandline: --performance-schema-digests-size=#
  • Scope: Global
  • Dynamic: No
  • Data Type: numeric
  • Default Value: -1
  • Range: -1 to 200

performance_schema_events_stages_history_long_size

  • Description: Number of rows in the events_stages_history_long table. 0 for disabling, -1 (the default) for automated sizing.
  • Commandline: --performance-schema-events-stages-history-long-size=#
  • Scope: Global
  • Dynamic: No
  • Data Type: numeric
  • Default Value: -1
  • Range: -1 to 1048576

performance_schema_events_stages_history_size

  • Description: Number of rows per thread in the events_stages_history table. 0 for disabling, -1 (the default) for automated sizing.
  • Commandline: --performance-schema-events-stages-history-size=#
  • Scope: Global
  • Dynamic: No
  • Data Type: numeric
  • Default Value: -1
  • Range: -1 to 1024

performance_schema_events_statements_history_long_size

  • Description: Number of rows in the events_statements_history_long table. 0 for disabling, -1 (the default) for automated sizing.
  • Commandline: --performance-schema-events-statements-history-long-size=#
  • Scope: Global
  • Dynamic: No
  • Data Type: numeric
  • Default Value: -1
  • Range: -1 to 1048576

performance_schema_events_statements_history_size

  • Description: Number of rows per thread in the events_statements_history table. 0 for disabling, -1 (the default) for automated sizing.
  • Commandline: --performance-schema-events-statements-history-size=#
  • Scope: Global
  • Dynamic: No
  • Data Type: numeric
  • Default Value: -1
  • Range: -1 to 1024

performance_schema_events_transactions_history_long_size

  • Description: Number of rows in events_transactions_history_long table. Use 0 to disable, -1 for automated sizing.
  • Commandline: --performance-schema-events-transactions-history-long-size=#
  • Scope: Global
  • Dynamic: No
  • Data Type: numeric
  • Default Value: -1
  • Range: -1 to 1048576
  • Introduced: MariaDB 10.5.2

performance_schema_events_transactions_history_size

  • Description:Number of rows per thread in events_transactions_history. Use 0 to disable, -1 for automated sizing.
  • Commandline: --performance-schema-events-transactions-history-size=#
  • Scope: Global
  • Dynamic: No
  • Data Type: numeric
  • Default Value: -1
  • Range: -1 to 1024
  • Introduced: MariaDB 10.5.2

performance_schema_events_waits_history_long_size

  • Description: Number of rows contained in the events_waits_history_long table. 0 for disabling, -1 (the default) for automated sizing.
  • Commandline: --performance-schema-events-waits-history-long-size=#
  • Scope: Global
  • Dynamic: No
  • Data Type: numeric
  • Default Value: -1
  • Range: -1 to 1048576

performance_schema_events_waits_history_size

  • Description: Number of rows per thread contained in the events_waits_history table. 0 for disabling, -1 (the default) for automated sizing.
  • Commandline: --performance-schema-events-waits-history-size=#
  • Scope: Global
  • Dynamic: No
  • Data Type: numeric
  • Default Value: -1
  • Range: -1 to 1024

performance_schema_hosts_size

  • Description: Number of rows stored in the hosts table. If set to zero, no connection statistics are kept for the hosts table. -1 (the default) for automated sizing.
  • Commandline: --performance-schema-hosts-size=#
  • Scope: Global
  • Dynamic: No
  • Data Type: numeric
  • Default Value: -1
  • Range: -1 to 1048576

performance_schema_max_cond_classes

  • Description: Specifies the maximum number of condition instruments.
  • Commandline: --performance-schema-max-cond-classes=#
  • Scope: Global
  • Dynamic: No
  • Data Type: numeric
  • Default Value: 90 (>= MariaDB 10.5.1), 80 (<= MariaDB 10.5.0)
  • Range: 0 to 256

performance_schema_max_cond_instances

  • Description: Specifies the maximum number of instrumented condition objects. 0 for disabling, -1 (the default) for automated sizing.
  • Commandline: --performance-schema-max-cond-instances=#
  • Scope: Global
  • Dynamic: No
  • Data Type: numeric
  • Default Value: -1
  • Range: -1 to 1048576

performance_schema_max_digest_length

  • Description: Maximum length considered for digest text, when stored in performance_schema tables.
  • Commandline: --performance-schema-max-digest-length=#
  • Scope: Global
  • Dynamic: No
  • Data Type: numeric
  • Default Value: 1024
  • Range: 0 to 1048576

performance_schema_max_file_classes

  • Description: Specifies the maximum number of file instruments.
  • Commandline: --performance-schema-max-file-classes=#
  • Scope: Global
  • Dynamic: No
  • Data Type: numeric
  • Default Value:80 (>= MariaDB 10.5.2), 50 (<= MariaDB 10.5.1)
  • Range: 0 to 256

performance_schema_max_file_handles

  • Description: Specifies the maximum number of opened file objects. Should always be higher than open_files_limit.
  • Commandline: --performance-schema-max-file-handles=#
  • Scope: Global
  • Dynamic: No
  • Data Type: numeric
  • Default Value: 32768
  • Range: -1 to 32768

performance_schema_max_file_instances

  • Description: Specifies the maximum number of instrumented file objects. 0 for disabling, -1 (the default) for automated sizing.
  • Commandline: --performance-schema-max-file-instances=#
  • Scope: Global
  • Dynamic: No
  • Data Type: numeric
  • Default Value: -1
  • Range: -1 to 1048576

performance_schema_max_index_stat

  • Description: Maximum number of index statistics for instrumented tables. Use 0 to disable, -1 for automated scaling.
  • Commandline: --performance-schema-max-index-stat=#
  • Scope: Global
  • Dynamic: No
  • Data Type: numeric
  • Default Value: -1
  • Range: -1 to 1048576
  • Introduced: MariaDB 10.5.2

performance_schema_max_memory_classes

  • Description: Maximum number of memory pool instruments.
  • Commandline: --performance-schema-max-memory-classes=#
  • Scope: Global
  • Dynamic: No
  • Data Type: numeric
  • Default Value: 320
  • Range: 0 to 1024
  • Introduced: MariaDB 10.5.2

performance_schema_max_metadata_locks

  • Description: Maximum number of Performance Schema metadata locks. Use 0 to disable, -1 for automated scaling.
  • Commandline: --performance-schema-max-metadata-locks=#
  • Scope: Global
  • Dynamic: No
  • Data Type: numeric
  • Default Value: -1
  • Range: -1 to 104857600
  • Introduced: MariaDB 10.5.2

performance_schema_max_mutex_classes

  • Description: Specifies the maximum number of mutex instruments.
  • Commandline: --performance-schema-max-mutex-classes=#
  • Scope: Global
  • Dynamic: No
  • Data Type: numeric
  • Default Value: 210 (>= MariaDB 10.5.2), 200 (<= MariaDB 10.5.1)
  • Range: 0 to 256

performance_schema_max_mutex_instances

  • Description: Specifies the maximum number of instrumented mutex instances. 0 for disabling, -1 (the default) for automated sizing.
  • Commandline: --performance-schema-max-mutex-instances=#
  • Scope: Global
  • Dynamic: No
  • Data Type: numeric
  • Default Value:-1
  • Range: -1 to 104857600

performance_schema_max_prepared_statement_instances

  • Description: Maximum number of instrumented prepared statements. Use 0 to disable, -1 for automated scaling.
  • Commandline: --performance-schema-max-prepared-statement-instances=#
  • Scope: Global
  • Dynamic: No
  • Data Type: numeric
  • Default Value: -1
  • Range: -1 to 1048576
  • Introduced: MariaDB 10.5.2

performance_schema_max_program_instances

  • Description: Maximum number of instrumented programs. Use 0 to disable, -1 for automated scaling.
  • Commandline: --performance-schema-max-program-instances=#
  • Scope: Global
  • Dynamic: No
  • Data Type: numeric
  • Default Value: -1
  • Range: -1 to 1048576
  • Introduced: MariaDB 10.5.2

performance_schema_max_rwlock_classes

  • Description: Specifies the maximum number of rwlock instruments.
  • Commandline: --performance-schema-max-rwlock-classes=#
  • Scope: Global
  • Dynamic: No
  • Data Type: numeric
  • Default Value: 50 (>= MariaDB 10.5.2), 40 (<= MariaDB 10.5.1)
  • Range: 0 to 256

performance_schema_max_rwlock_instances

  • Description: Specifies the maximum number of instrumented rwlock objects. 0 for disabling, -1 (the default) for automated sizing.
  • Commandline: --performance-schema-max-rwlock-instances=#
  • Scope: Global
  • Dynamic: No
  • Data Type: numeric
  • Default Value:-1
  • Range: -1 to 104857600

performance_schema_max_socket_classes

  • Description: Specifies the maximum number of socket instruments.
  • Commandline: --performance-schema-max-socket-classes=#
  • Scope: Global
  • Dynamic: No
  • Data Type: numeric
  • Default Value: 10
  • Range: 0 to 256

performance_schema_max_socket_instances

  • Description: Specifies the maximum number of instrumented socket objects. 0 for disabling, -1 (the default) for automated sizing.
  • Commandline: --performance-schema-max-socket-instances=#
  • Scope: Global
  • Dynamic: No
  • Data Type: numeric
  • Default Value:-1
  • Range: -1 to 1048576

performance_schema_max_sql_text_length

  • Description: Maximum length of displayed sql text.
  • Commandline: --performance-schema-max-sql-text-length=#
  • Scope: Global
  • Dynamic: No
  • Data Type: numeric
  • Default Value: 1024
  • Range: 0 to 1048576
  • Introduced: MariaDB 10.5.2

performance_schema_max_stage_classes

  • Description: Specifies the maximum number of stage instruments.
  • Commandline: --performance-schema-max-stage-classes=#
  • Scope: Global
  • Dynamic: No
  • Data Type: numeric
  • Default Value: 160 (>= MariaDB 10.3.3), 150 (<= MariaDB 10.3.2)
  • Range: 0 to 256

performance_schema_max_statement_classes

  • Description: Specifies the maximum number of statement instruments. Automatically calculated at server build based on the number of available statements. Should be left as either autosized or disabled, as changing to any positive value has no benefit and will most likely allocate unnecessary memory. Setting to zero disables all statement instrumentation, and no memory will be allocated for this purpose.
  • Commandline: --performance-schema-max-statement-classes=#
  • Scope: Global
  • Dynamic: No
  • Data Type: numeric
  • Default Value: Autosized (see description)
  • Range: 0 to 256

performance_schema_max_statement_stack

  • Description: Number of rows per thread in EVENTS_STATEMENTS_CURRENT.
  • Commandline: --performance-schema-max-statement-stack=#
  • Scope: Global
  • Dynamic: No
  • Data Type: numeric
  • Default Value: 10
  • Range: 1 to 256
  • Introduced: MariaDB 10.5.2

performance_schema_max_table_handles

  • Description: Specifies the maximum number of opened table objects. 0 for disabling, -1 (the default) for automated sizing.
  • Commandline: --performance-schema-max-table-handles=#
  • Scope: Global
  • Dynamic: No
  • Data Type: numeric
  • Default Value: -1
  • Range: -1 to 1048576

performance_schema_max_table_instances

  • Description: Specifies the maximum number of instrumented table objects. 0 for disabling, -1 (the default) for automated sizing.
  • Commandline: --performance-schema-max-table-instances=#
  • Scope: Global
  • Dynamic: No
  • Data Type: numeric
  • Default Value:-1
  • Range: -1 to 1048576

performance_schema_max_table_lock_stat

  • Description: Maximum number of lock statistics for instrumented tables. Use 0 to disable, -1 for automated scaling.
  • Commandline: --performance-schema-max-table-lock-stat=#
  • Scope: Global
  • Dynamic: No
  • Data Type: numeric
  • Default Value: -1
  • Range: -1 to 1048576
  • Introduced: MariaDB 10.5.2

performance_schema_max_thread_classes

  • Description: Specifies the maximum number of thread instruments.
  • Commandline: --performance-schema-max-thread-classes=#
  • Scope: Global
  • Dynamic: No
  • Data Type: numeric
  • Default Value: 50
  • Range: 0 to 256

performance_schema_max_thread_instances

  • Description: Specifies how many of the running server threads (see max_connections and max_delayed_threads) can be instrumented. Should be greater than the sum of max_connections and max_delayed_threads. 0 for disabling, -1 (the default) for automated sizing.
  • Commandline: --performance-schema-max-thread-instances=#
  • Scope: Global
  • Dynamic: No
  • Data Type: numeric
  • Default Value:-1
  • Range: -1 to 1048576

performance_schema_session_connect_attrs_size

  • Description: Per thread preallocated memory for holding connection attribute strings. Incremented if the strings are larger than the reserved space. 0 for disabling, -1 (the default) for automated sizing.
  • Commandline: --performance-schema-session-connect-attrs-size=#
  • Scope: Global
  • Dynamic: No
  • Data Type: numeric
  • Default Value: -1
  • Range: -1 to 1048576

performance_schema_setup_actors_size

performance_schema_setup_objects_size

performance_schema_users_size

  • Description: Number of rows in the performance_schema.users table. If set to 0, the Performance Schema will not store connection statistics in the users table. -1 (the default) for automated sizing.
  • Commandline: --performance-schema-users-size=#
  • Scope: Global
  • Dynamic: No
  • Data Type: numeric
  • Default Value: -1
  • Range: -1 to 1048576

1.1.1.2.9.2.5 Performance Schema Digests

The Performance Schema digest is a normalized form of a statement, with the specific data values removed. It allows statistics to be gathered for similar kinds of statements.

For example:

SELECT * FROM customer WHERE age < 20
SELECT * FROM customer WHERE age < 30

With the data values removed, both of these statements normalize to:

SELECT * FROM customer WHERE age < ?

which is the digest text. The digest text is then MD5 hashed, resulting in a digest. For example:

DIGEST_TEXT: SELECT * FROM `performance_schema` . `users`
DIGEST: 0f70cec4015f2a346df4ac0e9475d9f1

By contrast, the following two statements would not have the same digest as, while the data values are the same, they call upon different tables.

SELECT * FROM customer1 WHERE age < 20
SELECT * FROM customer2 WHERE age < 20

The digest text is limited to 1024 bytes. Queries exceeding this limit are truncated with '...', meaning that long queries that would otherwise have different digests may share the same digest.

Digest information is used in a number of performance scheme tables. These include

1.1.1.2.9.2.6 PERFORMANCE_SCHEMA Storage Engine

If you run SHOW ENGINES, you'll see the following storage engine listed.

SHOW ENGINES\G
...
      Engine: PERFORMANCE_SCHEMA
     Support: YES
     Comment: Performance Schema
Transactions: NO
          XA: NO
  Savepoints: NO
...

The PERFORMANCE_SCHEMA is not a regular storage engine for storing data, it's a mechanism for implementing the Performance Schema feature.

The SHOW ENGINE PERFORMANCE_SCHEMA STATUS statement is also available, which shows how much memory is used by the tables and internal buffers.

See Performance Schema for more details.

1.1.1.2.9.3 The mysql Database Tables

MariaDB comes pre-installed with a system database called mysql containing many important tables storing, in particular, grant and privilege information. Until MariaDB 10.4, system tables used the MyISAM storage engine. From MariaDB 10.4, they use Aria.

There are 2 related questions.

1.1.1.2.9.3.1 mysql.column_stats Table

The mysql.column_stats table is one of three tables storing data used for Engine-independent table statistics. The others are mysql.table_stats and mysql.index_stats.

Note that statistics for blob and text columns are not collected. If explicitly specified, a warning is returned.

MariaDB starting with 10.4

In MariaDB 10.4 and later, this table uses the Aria storage engine.

MariaDB until 10.3

In MariaDB 10.3 and before, this table uses the MyISAM storage engine.

The mysql.column_stats table contains the following fields:

FieldTypeNullKeyDefaultDescription
db_namevarchar(64)NOPRINULLDatabase the table is in.
table_namevarchar(64)NOPRINULLTable name.
column_namevarchar(64)NOPRINULLName of the column.
min_valuevarchar(255)YESNULLMinimum value in the table (in text form).
max_valuevarchar(255)YESNULLMaximum value in the table (in text form).
nulls_ratiodecimal(12,4)YESNULLFraction of NULL values (0- no NULLs, 0.5 - half values are NULLs, 1 - all values are NULLs).
avg_lengthdecimal(12,4)YESNULLAverage length of column value, in bytes. Counted as if one ran SELECT AVG(LENGTH(col)). This doesn't count NULL bytes, assumes endspace removal for CHAR(n), etc.
avg_frequencydecimal(12,4)YESNULLAverage number of records with the same value
hist_sizetinyint(3) unsignedYESNULLHistogram size in bytes, from 0-255, or, from MariaDB 10.7, number of buckets if the histogram type is JSON_HB.
hist_typeenum('SINGLE_PREC_HB', 'DOUBLE_PREC_HB') (>= MariaDB 10.7)
enum('SINGLE_PREC_HB', 'DOUBLE_PREC_HB','JSON_HB') (<= MariaDB 10.6)		YESNULLHistogram type. See the histogram_type system variable.
histogramblob (>= MariaDB 10.7)
varbinary(255) (<=MariaDB 10.6)		YESNULL

It is possible to manually update the table. See Manual updates to statistics tables for details.

1.1.1.2.9.3.2 mysql.columns_priv Table

The mysql.columns_priv table contains information about column-level privileges. The table can be queried and although it is possible to directly update it, it is best to use GRANT for setting privileges.

Note that the MariaDB privileges occur at many levels. A user may be granted a privilege at the column level, but may still not have permission on a table level, for example. See privileges for a more complete view of the MariaDB privilege system.

The INFORMATION_SCHEMA.COLUMN_PRIVILEGES table derives its contents from mysql.columns_priv.

MariaDB starting with 10.4

In MariaDB 10.4 and later, this table uses the Aria storage engine.

MariaDB until 10.3

In MariaDB 10.3 and before, this table uses the MyISAM storage engine.

The mysql.columns_priv table contains the following fields:

FieldTypeNullKeyDefaultDescription
Hostchar(60)NOPRIHost (together with User, Db , Table_name andColumn_name makes up the unique identifier for this record.
Dbchar(64)NOPRIDatabase name (together with User, Host , Table_name andColumn_name makes up the unique identifier for this record.
Userchar(80)NOPRIUser (together with Host, Db , Table_name andColumn_name makes up the unique identifier for this record.
Table_namechar(64)NOPRITable name (together with User, Db , Host andColumn_name makes up the unique identifier for this record.
Column_namechar(64)NOPRIColumn name (together with User, Db , Table_name andHost makes up the unique identifier for this record.
TimestamptimestampNOCURRENT_TIMESTAMP
Column_privset('Select', 'Insert', 'Update', 'References')NOThe privilege type. See Column Privileges for details.

The Acl_column_grants status variable, added in MariaDB 10.1.4, indicates how many rows the mysql.columns_priv table contains.

1.1.1.2.9.3.3 mysql.db Table

The mysql.db table contains information about database-level privileges. The table can be queried and although it is possible to directly update it, it is best to use GRANT for setting privileges.

Note that the MariaDB privileges occur at many levels. A user may not be granted a privilege at the database level, but may still have permission on a table level, for example. See privileges for a more complete view of the MariaDB privilege system.

MariaDB starting with 10.4

In MariaDB 10.4 and later, this table uses the Aria storage engine.

MariaDB until 10.3

In MariaDB 10.3 and before, this table uses the MyISAM storage engine.

The mysql.db table contains the following fields:

FieldTypeNullKeyDefaultDescriptionIntroduced
Hostchar(60)NOPRIHost (together with User and Db makes up the unique identifier for this record. Until MariaDB 5.5, if the host field was blank, the corresponding record in the mysql.host table would be examined. From MariaDB 10.0, a blank host field is the same as the % wildcard.
Dbchar(64)NOPRIDatabase (together with User and Host makes up the unique identifier for this record.
Userchar(80)NOPRIUser (together with Host and Db makes up the unique identifier for this record.
Select_privenum('N','Y')NONCan perform SELECT statements.
Insert_privenum('N','Y')NONCan perform INSERT statements.
Update_privenum('N','Y')NONCan perform UPDATE statements.
Delete_privenum('N','Y')NONCan perform DELETE statements.
Create_privenum('N','Y')NONCan CREATE TABLE's.
Drop_privenum('N','Y')NONCan DROP DATABASE's or DROP TABLE's.
Grant_privenum('N','Y')NONUser can grant privileges they possess.
References_privenum('N','Y')NONUnused
Index_privenum('N','Y')NONCan create an index on a table using the CREATE INDEX statement. Without the INDEX privilege, user can still create indexes when creating a table using the CREATE TABLE statement if the user has have the CREATE privilege, and user can create indexes using the ALTER TABLE statement if they have the ALTER privilege.
Alter_privenum('N','Y')NONCan perform ALTER TABLE statements.
Create_tmp_table_privenum('N','Y')NONCan create temporary tables with the CREATE TEMPORARY TABLE statement.
Lock_tables_privenum('N','Y')NONAcquire explicit locks using the LOCK TABLES statement; user also needs to have the SELECT privilege on a table in order to lock it.
Create_view_privenum('N','Y')NONCan create a view using the CREATE_VIEW statement.
Show_view_privenum('N','Y')NONCan show the CREATE VIEW statement to create a view using the SHOW CREATE VIEW statement.
Create_routine_privenum('N','Y')NONCan create stored programs using the CREATE PROCEDURE and CREATE FUNCTION statements.
Alter_routine_privenum('N','Y')NONCan change the characteristics of a stored function using the ALTER FUNCTION statement.
Execute_privenum('N','Y')NONCan execute stored procedure or functions.
Event_privenum('N','Y')NONCreate, drop and alter events.
Trigger_privenum('N','Y')NONCan execute triggers associated with tables the user updates, execute the CREATE TRIGGER and DROP TRIGGER statements.
Delete_history_privenum('N','Y')NONCan delete rows created through system versioning.MariaDB 10.3.5

The Acl_database_grants status variable, added in MariaDB 10.1.4, indicates how many rows the mysql.db table contains.

1.1.1.2.9.3.4 mysql.event Table

The mysql.event table contains information about MariaDB events. Similar information can be obtained by viewing the INFORMATION_SCHEMA.EVENTS table, or with the SHOW EVENTS and SHOW CREATE EVENT statements.

The table is upgraded live, and there is no need to restart the server if the table has changed.

MariaDB starting with 10.4

In MariaDB 10.4 and later, this table uses the Aria storage engine.

MariaDB until 10.3

In MariaDB 10.3 and before, this table uses the MyISAM storage engine.

The mysql.event table contains the following fields:

FieldTypeNullKeyDefaultDescription
dbchar(64)NOPRI
namechar(64)NOPRI
bodylongblobNONULL
definerchar(141)NO
execute_atdatetimeYESNULL
interval_valueint(11)YESNULL
interval_fieldenum('YEAR', 'QUARTER', 'MONTH', 'DAY', 'HOUR', 'MINUTE', 'WEEK', 'SECOND', 'MICROSECOND', 'YEAR_MONTH', 'DAY_HOUR', 'DAY_MINUTE', 'DAY_SECOND', 'HOUR_MINUTE', 'HOUR_SECOND', 'MINUTE_SECOND', 'DAY_MICROSECOND', 'HOUR_MICROSECOND', 'MINUTE_MICROSECOND', 'SECOND_MICROSECOND')YESNULL
createdtimestampNOCURRENT_TIMESTAMP
modifiedtimestampNO0000-00-00 00:00:00
last_executeddatetimeYESNULL
startsdatetimeYESNULL
endsdatetimeYESNULL
statusenum('ENABLED', 'DISABLED', 'SLAVESIDE_DISABLED')NOENABLEDCurrent status of the event, one of enabled, disabled, or disabled on the slaveside.
on_completionenum('DROP','PRESERVE')NODROP
sql_modeset('REAL_AS_FLOAT', 'PIPES_AS_CONCAT', 'ANSI_QUOTES', 'IGNORE_SPACE', 'IGNORE_BAD_TABLE_OPTIONS', 'ONLY_FULL_GROUP_BY', 'NO_UNSIGNED_SUBTRACTION', 'NO_DIR_IN_CREATE', 'POSTGRESQL', 'ORACLE', 'MSSQL', 'DB2', 'MAXDB', 'NO_KEY_OPTIONS', 'NO_TABLE_OPTIONS', 'NO_FIELD_OPTIONS', 'MYSQL323', 'MYSQL40', 'ANSI', 'NO_AUTO_VALUE_ON_ZERO', 'NO_BACKSLASH_ESCAPES', 'STRICT_TRANS_TABLES', 'STRICT_ALL_TABLES', 'NO_ZERO_IN_DATE', 'NO_ZERO_DATE', 'INVALID_DATES', 'ERROR_FOR_DIVISION_BY_ZERO', 'TRADITIONAL', 'NO_AUTO_CREATE_USER', 'HIGH_NOT_PRECEDENCE', 'NO_ENGINE_SUBSTITUTION', 'PAD_CHAR_TO_FULL_LENGTH')NOThe SQL_MODE at the time the event was created.
commentchar(64)NO
originatorint(10) unsignedNONULL
time_zonechar(64)NOSYSTEM
character_set_clientchar(32)YESNULL
collation_connectionchar(32)YESNULL
db_collationchar(32)YESNULL
body_utf8longblobYESNULL

1.1.1.2.9.3.5 mysql.func Table

The mysql.func table stores information about user-defined functions (UDFs) created with the CREATE FUNCTION UDF statement.

MariaDB starting with 10.4

In MariaDB 10.4 and later, this table uses the Aria storage engine.

MariaDB until 10.3

In MariaDB 10.3 and before, this table uses the MyISAM storage engine.

The mysql.func table contains the following fields:

FieldTypeNullKeyDefaultDescription
namechar(64)NOPRIUDF name
rettinyint(1)NO0
dlchar(128)NOShared library name
typeenum('function','aggregate')NONULLType, either function or aggregate. Aggregate functions are summary functions such as SUM() and AVG().

Example

SELECT * FROM mysql.func;
+------------------------------+-----+--------------+-----------+
| name                         | ret | dl           | type      |
+------------------------------+-----+--------------+-----------+
| spider_direct_sql            |   2 | ha_spider.so | function  |
| spider_bg_direct_sql         |   2 | ha_spider.so | aggregate |
| spider_ping_table            |   2 | ha_spider.so | function  |
| spider_copy_tables           |   2 | ha_spider.so | function  |
| spider_flush_table_mon_cache |   2 | ha_spider.so | function  |
+------------------------------+-----+--------------+-----------+

1.1.1.2.9.3.6 mysql.general_log Table

The mysql.general_log table stores the contents of the General Query Log if general logging is active and the output is being written to table (see Writing logs into tables).

It contains the following fields:

FieldTypeNullKeyDefaultDescription
event_timetimestamp(6)NOCURRENT_TIMESTAMP(6)Time the query was executed.
user_hostmediumtextNONULLUser and host combination.
thread_idint(11)NONULLThread id.
server_idint(10) unsignedNONULLServer id.
command_typevarchar(64)NONULLType of command.
argumentmediumtextNONULLFull query.

Example

SELECT * FROM mysql.general_log\G
*************************** 1. row ***************************
  event_time: 2014-11-11 08:40:04.117177
   user_host: root[root] @ localhost []
   thread_id: 74
   server_id: 1
command_type: Query
    argument: SELECT * FROM test.s
*************************** 2. row ***************************
  event_time: 2014-11-11 08:40:10.501131
   user_host: root[root] @ localhost []
   thread_id: 74
   server_id: 1
command_type: Query
    argument: SELECT * FROM mysql.general_log
...

1.1.1.2.9.3.7 mysql.global_priv Table

MariaDB starting with 10.4.1

The mysql.global_priv table was introduced in MariaDB 10.4.1 to replace the mysql.user table.

The mysql.global_priv table contains information about users that have permission to access the MariaDB server, and their global privileges.

Note that the MariaDB privileges occur at many levels. A user may not be granted create privilege at the user level, but may still have create permission on certain tables or databases, for example. See privileges for a more complete view of the MariaDB privilege system.

The mysql.global_priv table contains the following fields:

FieldTypeNullKeyDefaultDescription
Hostchar(60)NOPRIHost (together with User makes up the unique identifier for this account).
Userchar(80)NOPRIUser (together with Host makes up the unique identifier for this account).
PrivlongtextNOGlobal privileges, granted to the account and other account properties

From MariaDB 10.5.2, in order to help the server understand which version a privilege record was written by, the priv field contains a new JSON field, version_id (MDEV-21704).

Examples

select * from mysql.global_priv;
+-----------+-------------+---------------------------------------------------------------------------------------------------------------------------------------+
| Host      | User        | Priv                                                                                                                                  |
+-----------+-------------+---------------------------------------------------------------------------------------------------------------------------------------+
| localhost | root        | {"access": 18446744073709551615,"plugin":"mysql_native_password","authentication_string":"*6C387FC3893DBA1E3BA155E74754DA6682D04747"} |
| 127.%     | msandbox    | {"access":1073740799,"plugin":"mysql_native_password","authentication_string":"*6C387FC3893DBA1E3BA155E74754DA6682D04747"}            |
| localhost | msandbox    | {"access":1073740799,"plugin":"mysql_native_password","authentication_string":"*6C387FC3893DBA1E3BA155E74754DA6682D04747"}            |
| localhost | msandbox_rw | {"access":487487,"plugin":"mysql_native_password","authentication_string":"*6C387FC3893DBA1E3BA155E74754DA6682D04747"}                |
| 127.%     | msandbox_rw | {"access":487487,"plugin":"mysql_native_password","authentication_string":"*6C387FC3893DBA1E3BA155E74754DA6682D04747"}                |
| 127.%     | msandbox_ro | {"access":262145,"plugin":"mysql_native_password","authentication_string":"*6C387FC3893DBA1E3BA155E74754DA6682D04747"}                |
| localhost | msandbox_ro | {"access":262145,"plugin":"mysql_native_password","authentication_string":"*6C387FC3893DBA1E3BA155E74754DA6682D04747"}                |
| 127.%     | rsandbox    | {"access":524288,"plugin":"mysql_native_password","authentication_string":"*B07EB15A2E7BD9620DAE47B194D5B9DBA14377AD"}                |
+-----------+-------------+---------------------------------------------------------------------------------------------------------------------------------------+

Readable format:

SELECT CONCAT(user, '@', host, ' => ', JSON_DETAILED(priv)) FROM mysql.global_priv;

+--------------------------------------------------------------------------------------+
| CONCAT(user, '@', host, ' => ', JSON_DETAILED(priv))                                 |
+--------------------------------------------------------------------------------------+
| root@localhost => {
    "access": 18446744073709551615,
    "plugin": "mysql_native_password",
    "authentication_string": "*6C387FC3893DBA1E3BA155E74754DA6682D04747"
} |
| msandbox@127.% => {
    "access": 1073740799,
    "plugin": "mysql_native_password",
    "authentication_string": "*6C387FC3893DBA1E3BA155E74754DA6682D04747"
}           |
+--------------------------------------------------------------------------------------+

A particular user:

SELECT CONCAT(user, '@', host, ' => ', JSON_DETAILED(priv)) FROM mysql.global_priv 
  WHERE user='marijn';
+--------------------------------------------------------------------------------------+
| CONCAT(user, '@', host, ' => ', JSON_DETAILED(priv))                                 |
+--------------------------------------------------------------------------------------+
| marijn@localhost => {
    "access": 0,
    "plugin": "mysql_native_password",
    "authentication_string": "",
    "account_locked": true,
    "password_last_changed": 1558017158
} |
+--------------------------------------------------------------------------------------+

From MariaDB 10.5.2:

GRANT FILE ON *.* TO user1@localhost;
SELECT Host, User, JSON_DETAILED(Priv) FROM mysql.global_priv WHERE user='user1'\G

*************************** 1. row ***************************
               Host: localhost
               User: user1
JSON_DETAILED(Priv): {
    "access": 512,
    "plugin": "mysql_native_password",
    "authentication_string": "",
    "password_last_changed": 1581070979,
    "version_id": 100502
}

1.1.1.2.9.3.8 mysql.gtid_slave_pos Table

The mysql.gtid_slave_pos table is used in replication by replica servers to keep track of their current position (the global transaction ID of the last transaction applied). Using the table allows the replica to maintain a consistent value for the gtid_slave_pos system variable across server restarts. See Global Transaction ID.

You should never attempt to modify the table directly. If you do need to change the global gtid_slave_pos value, use SET GLOBAL gtid_slave_pos = ... instead.

The table is updated with the new position as part of each transaction committed during replication. This makes it preferable that the table is using the same storage engine as the tables otherwise being modified in the transaction, since otherwise a multi-engine transaction is needed that can reduce performance.

Starting from MariaDB 10.3.1, multiple versions of this table are supported, each using a different storage engine. This is selected with the gtid_pos_auto_engines option, by giving a comma-separated list of engine names. The server will then on-demand create an extra version of the table using the appropriate storage engine, and select the table version using the same engine as the rest of the transaction, avoiding multi-engine transactions.

For example, when gtid_pos_auto_engines=innodb,rocksdb, tables mysql.gtid_slave_pos_InnoDB and mysql.gtid_slave_pos_RocksDB will be created and used, if needed. If there is no match to the storage engine, the default mysql.gtid_slave_pos table will be used; this also happens if non-transactional updates (like MyISAM) are replicated, since there is then no active transaction at the time of the mysql.gtid_slave_pos table update.

Prior to MariaDB 10.3.1, only the default mysql.gtid_slave_pos table is available. In these versions, the table should preferably be using the storage engine that is used for most replicated transactions.

The default mysql.gtid_slave_pos table will be initially created using the default storage engine set for the server (which itself defaults to InnoDB). If the application load is primarily non-transactional MyISAM or Aria tables, it can be beneficial to change the storage engine to avoid including an InnoDB update with every operation:

ALTER TABLE mysql.gtid_slave_pos ENGINE=MyISAM;

The mysql.gtid_slave_pos table should not be changed manually in any other way. From MariaDB 10.3.1, it is preferable to use the gtid_pos_auto_engines server variable to get the GTID position updates to use the TokuDB or RocksDB storage engine.

Note that for scalability reasons, the automatic creation of a new mysql.gtid_slave_posXXX table happens asynchronously when the first transaction with the new storage engine is committed. So the very first few transactions will update the old version of the table, until the new version is created and available.

The table mysql.gtid_slave_pos contains the following fields

FieldTypeNullKeyDefaultDescription
domain_idint(10) unsignedNOPRINULLDomain id (see Global Transaction ID domain ID.
sub_idbigint(20) unsignedNOPRINULLThis field enables multiple parallel transactions within same domain_id to update this table without contention. At any instant, the replication state corresponds to records with largest sub_id for each domain_id.
server_idint(10) unsignedNONULLServer id.
seq_nobigint(20) unsignedNONULLSequence number, an integer that is monotonically increasing for each new event group logged into the binlog.

From MariaDB 10.3.1, some status variables are available to monitor the use of the different gtid_slave_pos table versions:

Transactions_gtid_foreign_engine

Number of replicated transactions where the update of the gtid_slave_pos table had to choose a storage engine that did not otherwise participate in the transaction. This can indicate that setting gtid_pos_auto_engines might be useful.

Rpl_transactions_multi_engine

Number of replicated transactions that involved changes in multiple (transactional) storage engines, before considering the update of gtid_slave_pos. These are transactions that were already cross-engine, independent of the GTID position update introduced by replication

Transactions_multi_engine

Number of transactions that changed data in multiple (transactional) storage engines. If this is significantly larger than Rpl_transactions_multi_engine, it indicates that setting gtid_pos_auto_engines could reduce the need for cross-engine transactions.

1.1.1.2.9.3.9 mysql.help_category Table

mysql.help_category is one of the four tables used by the HELP command. It is populated when the server is installed by the fill_help_table.sql script. The other help tables are help_relation, help_topic and help_keyword.

MariaDB starting with 10.4

In MariaDB 10.4 and later, this table uses the Aria storage engine.

MariaDB until 10.3

In MariaDB 10.3 and before, this table uses the MyISAM storage engine.

The mysql.help_category table contains the following fields:

FieldTypeNullKeyDefaultDescription
help_category_idsmallint(5) unsignedNOPRINULL
namechar(64)NOUNINULL
parent_category_idsmallint(5) unsignedYESNULL
urlchar(128)NONULL

Example

SELECT * FROM help_category;
+------------------+-----------------------------------------------+--------------------+-----+
| help_category_id | name                                          | parent_category_id | url |
+------------------+-----------------------------------------------+--------------------+-----+
|                1 | Geographic                                    |                  0 |     |
|                2 | Polygon properties                            |                 34 |     |
|                3 | WKT                                           |                 34 |     |
|                4 | Numeric Functions                             |                 38 |     |
|                5 | Plugins                                       |                 35 |     |
|                6 | MBR                                           |                 34 |     |
|                7 | Control flow functions                        |                 38 |     |
|                8 | Transactions                                  |                 35 |     |
|                9 | Help Metadata                                 |                 35 |     |
|               10 | Account Management                            |                 35 |     |
|               11 | Point properties                              |                 34 |     |
|               12 | Encryption Functions                          |                 38 |     |
|               13 | LineString properties                         |                 34 |     |
|               14 | Miscellaneous Functions                       |                 38 |     |
|               15 | Logical operators                             |                 38 |     |
|               16 | Functions and Modifiers for Use with GROUP BY |                 35 |     |
|               17 | Information Functions                         |                 38 |     |
|               18 | Comparison operators                          |                 38 |     |
|               19 | Bit Functions                                 |                 38 |     |
|               20 | Table Maintenance                             |                 35 |     |
|               21 | User-Defined Functions                        |                 35 |     |
|               22 | Data Types                                    |                 35 |     |
|               23 | Compound Statements                           |                 35 |     |
|               24 | Geometry constructors                         |                 34 |     |
|               25 | GeometryCollection properties                 |                  1 |     |
|               26 | Administration                                |                 35 |     |
|               27 | Data Manipulation                             |                 35 |     |
|               28 | Utility                                       |                 35 |     |
|               29 | Language Structure                            |                 35 |     |
|               30 | Geometry relations                            |                 34 |     |
|               31 | Date and Time Functions                       |                 38 |     |
|               32 | WKB                                           |                 34 |     |
|               33 | Procedures                                    |                 35 |     |
|               34 | Geographic Features                           |                 35 |     |
|               35 | Contents                                      |                  0 |     |
|               36 | Geometry properties                           |                 34 |     |
|               37 | String Functions                              |                 38 |     |
|               38 | Functions                                     |                 35 |     |
|               39 | Data Definition                               |                 35 |     |
+------------------+-----------------------------------------------+--------------------+-----+

1.1.1.2.9.3.10 mysql.help_keyword Table

mysql.help_keyword is one of the four tables used by the HELP command. It is populated when the server is installed by the fill_help_table.sql script. The other help tables are help_relation, help_category and help_topic.

MariaDB starting with 10.4

In MariaDB 10.4 and later, this table uses the Aria storage engine.

MariaDB until 10.3

In MariaDB 10.3 and before, this table uses the MyISAM storage engine.

The mysql.help_keyword table contains the following fields:

FieldTypeNullKeyDefaultDescription
help_keyword_idint(10) unsignedNOPRINULL
namechar(64)NOUNINULL

Example

SELECT * FROM help_keyword;
+-----------------+-------------------------------+
| help_keyword_id | name                          |
+-----------------+-------------------------------+
|               0 | JOIN                          |
|               1 | HOST                          |
|               2 | REPEAT                        |
|               3 | SERIALIZABLE                  |
|               4 | REPLACE                       |
|               5 | AT                            |
|               6 | SCHEDULE                      |
|               7 | RETURNS                       |
|               8 | STARTS                        |
|               9 | MASTER_SSL_CA                 |
|              10 | NCHAR                         |
|              11 | COLUMNS                       |
|              12 | COMPLETION                    |
...

1.1.1.2.9.3.11 mysql.help_relation Table

mysql.help_relation is one of the four tables used by the HELP command. It is populated when the server is installed by the fill_help_table.sql script. The other help tables are help_topic, help_category and help_keyword.

MariaDB starting with 10.4

In MariaDB 10.4 and later, this table uses the Aria storage engine.

MariaDB until 10.3

In MariaDB 10.3 and before, this table uses the MyISAM storage engine.

The mysql.help_relation table contains the following fields:

FieldTypeNullKeyDefaultDescription
help_topic_idint(10) unsignedNOPRINULL
help_keyword_idint(10) unsignedNOPRINULL

Example

...
|           106 |             456 |
|           463 |             456 |
|           468 |             456 |
|           463 |             457 |
|           194 |             458 |
|           478 |             458 |
|           374 |             459 |
|           459 |             459 |
|            39 |             460 |
|            58 |             460 |
|           185 |             460 |
|           264 |             460 |
|           269 |             460 |
|           209 |             461 |
|           468 |             461 |
|           201 |             462 |
|           468 |             463 |
+---------------+-----------------+

1.1.1.2.9.3.12 mysql.help_topic Table

mysql.help_topic is one of the four tables used by the HELP command. It is populated when the server is installed by the fill_help_table.sql script. The other help tables are help_relation, help_category and help_keyword.

MariaDB starting with 10.4

In MariaDB 10.4 and later, this table uses the Aria storage engine.

MariaDB until 10.3

In MariaDB 10.3 and before, this table uses the MyISAM storage engine.

The mysql.help_topic table contains the following fields:

FieldTypeNullKeyDefaultDescription
help_topic_idint(10) unsignedNOPRINULL
namechar(64)NOUNINULL
help_category_idsmallint(5) unsignedNONULL
descriptiontextNONULL
exampletextNONULL
urlchar(128)NONULL

Example

SELECT * FROM help_topic\G;
...
*************************** 704. row ***************************
   help_topic_id: 692
            name: JSON_DEPTH
help_category_id: 41
     description: JSON functions were added in MariaDB 10.2.3.
 
Syntax
------ 
JSON_DEPTH(json_doc)
 
Description
----------- 
Returns the maximum depth of the given JSON document, or
NULL if the argument is null. An error will occur if the
argument is an invalid JSON document.
Scalar values or empty arrays or objects have a depth of 1.
Arrays or objects that are not empty but contain only
elements or member values of depth 1 will have a depth of 2.
In other cases, the depth will be greater than 2.
 
Examples
-------- 
SELECT JSON_DEPTH('[]'), JSON_DEPTH('true'),
JSON_DEPTH('{}');
+------------------+--------------------+------------------+
| JSON_DEPTH('[]') | JSON_DEPTH('true') |
JSON_DEPTH('{}') |
+------------------+--------------------+------------------+
| 1 | 1 | 1 |
+------------------+--------------------+------------------+
 
SELECT JSON_DEPTH('[1, 2, 3]'), JSON_DEPTH('[[], {},
[]]');
+-------------------------+----------------------------+
| JSON_DEPTH('[1, 2, 3]') | JSON_DEPTH('[[], {}, []]') |
+-------------------------+----------------------------+
| 2 | 2 |
+-------------------------+----------------------------+
 
SELECT JSON_DEPTH('[1, 2, [3, 4, 5, 6], 7]');
+---------------------------------------+
| JSON_DEPTH('[1, 2, [3, 4, 5, 6], 7]') |
+---------------------------------------+
| 3 |
+---------------------------------------+

URL: https://mariadb.com/kb/en/json_depth/
         example: 
             url: https://mariadb.com/kb/en/json_depth/

1.1.1.2.9.3.13 mysql.index_stats Table

The mysql.index_stats table is one of three tables storing data used for Engine-independent table statistics. The others are mysql.column_stats and mysql.table_stats.

MariaDB starting with 10.4

In MariaDB 10.4 and later, this table uses the Aria storage engine.

MariaDB until 10.3

In MariaDB 10.3 and before, this table uses the MyISAM storage engine.

The mysql.index_stats table contains the following fields:

FieldTypeNullKeyDefaultDescription
db_namevarchar(64)NOPRINULLDatabase the table is in.
table_namevarchar(64)NOPRINULLTable name
index_namevarchar(64)NOPRINULLName of the index
prefix_arityint(11) unsignedNOPRINULLIndex prefix length. 1 for the first keypart, 2 for the first two, and so on. InnoDB's extended keys are supported.
avg_frequencydecimal(12,4)YESNULLAverage number of records one will find for given values of (keypart1, keypart2, ..), provided the values will be found in the table.

It is possible to manually update the table. See Manual updates to statistics tables for details.

1.1.1.2.9.3.14 mysql.innodb_index_stats

Contents

  1. Example
  2. See Also

The mysql.innodb_index_stats table stores data related to particular InnoDB Persistent Statistics, and contains multiple rows for each index.

This table, along with the related mysql.innodb_table_stats table, can be manually updated in order to force or test differing query optimization plans. After updating, FLUSH TABLE innodb_index_stats is required to load the changes.

mysql.innodb_index_stats is not replicated, although any ANALYZE TABLE statements on the table will be by default..

It contains the following fields:

FieldTypeNullKeyDefaultDescription
database_namevarchar(64)NOPRINULLDatabase name.
table_namevarchar(64)NOPRINULLTable, partition or subpartition name.
index_namevarchar(64)NOPRINULLIndex name.
last_updatetimestampNOcurrent_timestamp()Time that this row was last updated.
stat_namevarchar(64)NOPRINULLStatistic name.
stat_valuebigint(20) unsignedNONULLEstimated statistic value.
sample_sizebigint(20) unsignedYESNULLNumber of pages sampled for the estimated statistic value.
stat_descriptionvarchar(1024)NONULLStatistic description.

Example

SELECT * FROM mysql.innodb_index_stats\G
*************************** 1. row ***************************
   database_name: mysql
      table_name: gtid_slave_pos
      index_name: PRIMARY
     last_update: 2017-08-19 20:38:34
       stat_name: n_diff_pfx01
      stat_value: 0
     sample_size: 1
stat_description: domain_id
*************************** 2. row ***************************
   database_name: mysql
      table_name: gtid_slave_pos
      index_name: PRIMARY
     last_update: 2017-08-19 20:38:34
       stat_name: n_diff_pfx02
      stat_value: 0
     sample_size: 1
stat_description: domain_id,sub_id
*************************** 3. row ***************************
   database_name: mysql
      table_name: gtid_slave_pos
      index_name: PRIMARY
     last_update: 2017-08-19 20:38:34
       stat_name: n_leaf_pages
      stat_value: 1
     sample_size: NULL
stat_description: Number of leaf pages in the index
*************************** 4. row ***************************
   database_name: mysql
      table_name: gtid_slave_pos
      index_name: PRIMARY
     last_update: 2017-08-19 20:38:34
       stat_name: size
      stat_value: 1
     sample_size: NULL
stat_description: Number of pages in the index
*************************** 5. row ***************************
   database_name: test
      table_name: ft
      index_name: FTS_DOC_ID_INDEX
     last_update: 2017-09-15 12:58:39
       stat_name: n_diff_pfx01
      stat_value: 0
     sample_size: 1
stat_description: FTS_DOC_ID
*************************** 6. row ***************************
   database_name: test
      table_name: ft
      index_name: FTS_DOC_ID_INDEX
     last_update: 2017-09-15 12:58:39
       stat_name: n_leaf_pages
      stat_value: 1
     sample_size: NULL
stat_description: Number of leaf pages in the index
...

See Also

1.1.1.2.9.3.15 mysql.innodb_table_stats

Contents

  1. Example
  2. See Also

The mysql.innodb_table_stats table stores data related to InnoDB Persistent Statistics, and contains one row per table.

This table, along with the related mysql.innodb_index_stats table, can be manually updated in order to force or test differing query optimization plans. After updating, FLUSH TABLE innodb_table_stats is required to load the changes.

mysql.innodb_table_stats is not replicated, although any ANALYZE TABLE statements on the table will be by default..

It contains the following fields:

FieldTypeNullKeyDefaultDescription
database_namevarchar(64)NOPRINULLDatabase name.
table_name varchar(64)NOPRINULLTable, partition or subpartition name.
last_updatetimestampNOcurrent_timestamp()Time that this row was last updated.
n_rowsbigint(20) unsignedNONULLNumber of rows in the table.
clustered_index_sizebigint(20) unsignedNONULLSize, in pages, of the primary index.
sum_of_other_index_sizesbigint(20) unsignedNONULLSize, in pages, of non-primary indexes.

Example

SELECT * FROM mysql.innodb_table_stats\G
*************************** 1. row ***************************
           database_name: mysql
              table_name: gtid_slave_pos
             last_update: 2017-08-19 20:38:34
                  n_rows: 0
    clustered_index_size: 1
sum_of_other_index_sizes: 0
*************************** 2. row ***************************
           database_name: test
              table_name: ft
             last_update: 2017-09-15 12:58:39
                  n_rows: 0
    clustered_index_size: 1
sum_of_other_index_sizes: 2
...

See Also

1.1.1.2.9.3.16 mysql.password_reuse_check_history Table

MariaDB starting with 10.7.0

The mysql.password_reuse_check_history Table is installed as part of the password_reuse_check plugin, available from MariaDB 10.7.0.

The mysql.password_reuse_check_history table stores old passwords, so that when a user sets a new password, it can be checked for purposes of preventing password reuse.

It contains the following fields:

FieldTypeNullKeyDefaultDescription
hashbinary(64)NOPRINULL
timetimestampNOMULcurrent_timestamp()

1.1.1.2.9.3.17 mysql.plugin Table

The mysql.plugin table can be queried to get information about installed plugins.

This table only contains information about plugins that have been installed via the following methods:

This table does not contain information about:

This table only contains enough information to reload the plugin when the server is restarted, which means it only contains the plugin name and the plugin library.

MariaDB starting with 10.4

In MariaDB 10.4 and later, this table uses the Aria storage engine.

MariaDB until 10.3

In MariaDB 10.3 and before, this table uses the MyISAM storage engine.

The mysql.plugin table contains the following fields:

FieldTypeNullKeyDefaultDescription
namevarchar(64)NOPRIPlugin name.
dlvarchar(128)NOName of the plugin library.

Example

SELECT * FROM mysql.plugin;
+---------------------------+------------------------+
| name                      | dl                     |
+---------------------------+------------------------+
| spider                    | ha_spider.so           |
| spider_alloc_mem          | ha_spider.so           |
| METADATA_LOCK_INFO        | metadata_lock_info.so  |
| OQGRAPH                   | ha_oqgraph.so          |
| cassandra                 | ha_cassandra.so        |
| QUERY_RESPONSE_TIME       | query_response_time.so |
| QUERY_RESPONSE_TIME_AUDIT | query_response_time.so |
| LOCALES                   | locales.so             |
| sequence                  | ha_sequence.so         |
+---------------------------+------------------------+

1.1.1.2.9.3.18 mysql.proc Table

The mysql.proc table contains information about stored procedures and stored functions. It contains similar information to that stored in the INFORMATION SCHEMA.ROUTINES table.

MariaDB starting with 10.4

In MariaDB 10.4 and later, this table uses the Aria storage engine.

MariaDB until 10.3

In MariaDB 10.3 and before, this table uses the MyISAM storage engine.

The mysql.proc table contains the following fields:

FieldTypeNullKeyDefaultDescription
dbchar(64)NOPRIDatabase name.
namechar(64)NOPRIRoutine name.
typeenum('FUNCTION','PROCEDURE','PACKAGE', 'PACKAGE BODY')NOPRINULLWhether stored procedure, stored function or, from MariaDB 10.3.5, a package or package body.
specific_namechar(64)NO
languageenum('SQL')NOSQLAlways SQL.
sql_data_accessenum('CONTAINS_SQL', 'NO_SQL', 'READS_SQL_DATA', 'MODIFIES_SQL_DATA')NOCONTAINS_SQL
is_deterministicenum('YES','NO')NONOWhether the routine is deterministic (can produce only one result for a given list of parameters) or not.
security_typeenum('INVOKER','DEFINER')NODEFINERINVOKER or DEFINER. Indicates which user's privileges apply to this routine.
param_listblobNONULLList of parameters.
returnslongblobNONULLWhat the routine returns.
bodylongblobNONULLDefinition of the routine.
definerchar(141)NOIf the security_type is DEFINER, this value indicates which user defined this routine.
createdtimestampNOCURRENT_TIMESTAMPDate and time the routine was created.
modifiedtimestampNO0000-00-00 00:00:00Date and time the routine was modified.
sql_modeset('REAL_AS_FLOAT', 'PIPES_AS_CONCAT', 'ANSI_QUOTES', 'IGNORE_SPACE', 'IGNORE_BAD_TABLE_OPTIONS', 'ONLY_FULL_GROUP_BY', 'NO_UNSIGNED_SUBTRACTION', 'NO_DIR_IN_CREATE', 'POSTGRESQL', 'ORACLE', 'MSSQL', 'DB2', 'MAXDB', 'NO_KEY_OPTIONS', 'NO_TABLE_OPTIONS', 'NO_FIELD_OPTIONS', 'MYSQL323', 'MYSQL40', 'ANSI', 'NO_AUTO_VALUE_ON_ZERO', 'NO_BACKSLASH_ESCAPES', 'STRICT_TRANS_TABLES', 'STRICT_ALL_TABLES', 'NO_ZERO_IN_DATE', 'NO_ZERO_DATE', 'INVALID_DATES', 'ERROR_FOR_DIVISION_BY_ZERO', 'TRADITIONAL', 'NO_AUTO_CREATE_USER', 'HIGH_NOT_PRECEDENCE', 'NO_ENGINE_SUBSTITUTION', 'PAD_CHAR_TO_FULL_LENGTH', 'EMPTY_STRING_IS_NULL', 'SIMULTANEOUS_ASSIGNMENT')NOThe SQL_MODE at the time the routine was created.
commenttextNONULLComment associated with the routine.
character_set_clientchar(32)YESNULLThe character set used by the client that created the routine.
collation_connectionchar(32)YESNULLThe collation (and character set) used by the connection that created the routine.
db_collationchar(32)YESNULLThe default collation (and character set) for the database, at the time the routine was created.
body_utf8longblobYESNULLDefinition of the routine in utf8.
aggregateenum('NONE', 'GROUP')NONONEFrom MariaDB 10.3.3
FieldTypeNullKeyDefaultDescription

See Also

1.1.1.2.9.3.19 mysql.procs_priv Table

The mysql.procs_priv table contains information about stored procedure and stored function privileges. See CREATE PROCEDURE and CREATE FUNCTION on creating these.

The INFORMATION_SCHEMA.ROUTINES table derives its contents from mysql.procs_priv.

MariaDB starting with 10.4

In MariaDB 10.4 and later, this table uses the Aria storage engine.

MariaDB until 10.3

In MariaDB 10.3 and before, this table uses the MyISAM storage engine.

The mysql.procs_priv table contains the following fields:

FieldTypeNullKeyDefaultDescription
Hostchar(60)NOPRIHost (together with Db, User, Routine_name and Routine_type makes up the unique identifier for this record).
Dbchar(64)NOPRIDatabase (together with Host, User, Routine_name and Routine_type makes up the unique identifier for this record).
Userchar(80)NOPRIUser (together with Host, Db, Routine_name and Routine_type makes up the unique identifier for this record).
Routine_namechar(64)NOPRIRoutine_name (together with Host, Db User and Routine_type makes up the unique identifier for this record).
Routine_typeenum('FUNCTION','PROCEDURE', 'PACKAGE', 'PACKAGE BODY')NOPRINULLWhether the routine is a stored procedure, stored function, or, from MariaDB 10.3.5, a package or package body.
Grantorchar(141)NOMUL
Proc_privset('Execute','Alter Routine','Grant')NOThe routine privilege. See Function Privileges and Procedure Privileges for details.
TimestamptimestampNOCURRENT_TIMESTAMP

The Acl_function_grants status variable, added in MariaDB 10.1.4, indicates how many rows the mysql.columns_priv table contains with the FUNCTION routine type.

The Acl_procedure_grants status variable, added in MariaDB 10.1.4, indicates how many rows the mysql.columns_priv table contains with the PROCEDURE routine type.

1.1.1.2.9.3.20 mysql.roles_mapping Table

The mysql.roles_mapping table contains information about mariaDB roles.

MariaDB starting with 10.4

In MariaDB 10.4 and later, this table uses the Aria storage engine.

MariaDB until 10.3

In MariaDB 10.3 and before, this table uses the MyISAM storage engine.

The mysql.roles_mapping table contains the following fields:

FieldTypeNullKeyDefaultDescription
Hostchar(60)NOPRIHost (together with User and Role makes up the unique identifier for this record.
Userchar(80)NOPRIUser (together with Host and Role makes up the unique identifier for this record.
Rolechar(80)NOPRIRole (together with Host and User makes up the unique identifier for this record.
Admin_optionenum('N','Y')NONWhether the role can be granted (see the CREATE ROLE WITH ADMIN clause).

The Acl_role_grants status variable, added in MariaDB 10.1.4, indicates how many rows the mysql.roles_mapping table contains.

1.1.1.2.9.3.21 mysql.servers Table

The mysql.servers table contains information about servers as used by the Spider, FEDERATED or FederatedX, Connect storage engines (see CREATE SERVER).

MariaDB starting with 10.4

In MariaDB 10.4 and later, this table uses the Aria storage engine.

MariaDB until 10.3

In MariaDB 10.3 and before, this table uses the MyISAM storage engine.

The mysql.servers table contains the following fields:

FieldTypeNullKeyDefaultDescription
Server_namechar(64)NOPRI
Hostchar(64)NO
Dbchar(64)NO
Usernamechar(80)NO
Passwordchar(64)NO
Portint(4)NO0
Socketchar(64)NO
Wrapperchar(64)NOmysql or mariadb
Ownerchar(64)NO

1.1.1.2.9.3.22 mysql.slow_log Table

The mysql.slow_log table stores the contents of the Slow Query Log if slow logging is active and the output is being written to table (see Writing logs into tables).

It contains the following fields:

FieldTypeNullKeyDefaultDescription
start_timetimestamp(6)NOCURRENT_TIMESTAMP(6)Time the query began.
user_hostmediumtextNONULLUser and host combination.
query_timetime(6)NONULLTotal time the query took to execute.
lock_timetime(6)NONULLTotal time the query was locked.
rows_sentint(11)NONULLNumber of rows sent.
rows_examinedint(11)NONULLNumber of rows examined.
dbvarchar(512)NONULLDefault database.
last_insert_idint(11)NONULLlast_insert_id.
insert_idint(11)NONULLInsert id.
server_idint(10) unsignedNONULLThe server's id.
sql_textmediumtextNONULLFull query.
thread_idbigint(21) unsignedNONULLThread id.
rows_affectedint(11)NONULLNumber of rows affected by an UPDATE or DELETE (from MariaDB 10.1.2)

Example

SELECT * FROM mysql.slow_log\G
...
*************************** 2. row ***************************
    start_time: 2014-11-11 07:56:28.721519
     user_host: root[root] @ localhost []
    query_time: 00:00:12.000215
     lock_time: 00:00:00.000000
     rows_sent: 1
 rows_examined: 0
            db: test
last_insert_id: 0
     insert_id: 0
     server_id: 1
      sql_text: SELECT SLEEP(12)
     thread_id: 74
...

1.1.1.2.9.3.23 mysql.tables_priv Table

The mysql.tables_priv table contains information about table-level privileges. The table can be queried and although it is possible to directly update it, it is best to use GRANT for setting privileges.

Note that the MariaDB privileges occur at many levels. A user may be granted a privilege at the table level, but may still not have permission on a database level, for example. See privileges for a more complete view of the MariaDB privilege system.

The INFORMATION_SCHEMA.TABLE_PRIVILEGES table derives its contents from mysql.tables_priv.

MariaDB starting with 10.4

In MariaDB 10.4 and later, this table uses the Aria storage engine.

MariaDB until 10.3

In MariaDB 10.3 and before, this table uses the MyISAM storage engine.

The mysql.tables_priv table contains the following fields:

FieldTypeNullKeyDefaultDescription
Hostchar(60)NOPRIHost (together with User, Db and Table_namemakes up the unique identifier for this record.
Dbchar(64)NOPRIDatabase (together with User, Host and Table_namemakes up the unique identifier for this record.
Userchar(80)NOPRIUser (together with Host, Db and Table_namemakes up the unique identifier for this record.
Table_namechar(64)NOPRITable name (together with User, Db and Tablemakes up the unique identifier for this record.
Grantorchar(141)NOMUL
TimestamptimestampNOCURRENT_TIMESTAMP
Table_privset('Select', 'Insert', 'Update', 'Delete', 'Create', 'Drop', 'Grant', 'References', 'Index', 'Alter', 'Create View', 'Show view', 'Trigger', 'Delete versioning rows')NOThe table privilege type. See Table Privileges for details.
Column_privset('Select', 'Insert', 'Update', 'References')NOThe column privilege type. See Column Privileges for details.

The Acl_table_grants status variable, added in MariaDB 10.1.4, indicates how many rows the mysql.tables_priv table contains.

1.1.1.2.9.3.24 mysql.table_stats Table

The mysql.table_stats table is one of three tables storing data used for Engine-independent table statistics. The others are mysql.column_stats and mysql.index_stats.

MariaDB starting with 10.4

In MariaDB 10.4 and later, this table uses the Aria storage engine.

MariaDB until 10.3

In MariaDB 10.3 and before, this table uses the MyISAM storage engine.

The mysql.table_stats table contains the following fields:

FieldTypeNullKeyDefaultDescription
db_namevarchar(64)NOPRINULLDatabase the table is in .
table_namevarchar(64)NOPRINULLTable name.
cardinalitybigint(21) unsignedYESNULLNumber of records in the table.

It is possible to manually update the table. See Manual updates to statistics tables for details.

1.1.1.2.9.3.25 mysql.time_zone Table

The mysql.time_zone table is one of the mysql system tables that can contain time zone information. It is usually preferable for the system to handle the time zone, in which case the table will be empty (the default), but you can populate the mysql time zone tables using the mysql_tzinfo_to_sql utility. See Time Zones for details.

MariaDB starting with 10.4

In MariaDB 10.4 and later, this table uses the Aria storage engine.

MariaDB until 10.3

In MariaDB 10.3 and before, this table uses the MyISAM storage engine.

The mysql.time_zone table contains the following fields:

FieldTypeNullKeyDefaultDescription
Time_zone_idint(10) unsignedNOPRINULLID field, auto_increments.
Use_leap_secondsenum('Y','N')NONWhether or not leap seconds are used.

Example

SELECT * FROM mysql.time_zone;
+--------------+------------------+
| Time_zone_id | Use_leap_seconds |
+--------------+------------------+
|            1 | N                |
|            2 | N                |
|            3 | N                |
|            4 | N                |
|            5 | N                |
|            6 | N                |
|            7 | N                |
|            8 | N                |
|            9 | N                |
|           10 | N                |
...
+--------------+------------------+

See Also

1.1.1.2.9.3.26 mysql.time_zone_leap_second Table

The mysql.time_zone_leap_second table is one of the mysql system tables that can contain time zone information. It is usually preferable for the system to handle the time zone, in which case the table will be empty (the default), but you can populate the mysql time zone tables using the mysql_tzinfo_to_sql utility. See Time Zones for details.

MariaDB starting with 10.4

In MariaDB 10.4 and later, this table uses the Aria storage engine.

MariaDB until 10.3

In MariaDB 10.3 and before, this table uses the MyISAM storage engine.

The mysql.time_zone_leap_second table contains the following fields:

FieldTypeNullKeyDefaultDescription
Transition_timebigint(20)NOPRINULL
Correctionint(11)NONULL

See Also

1.1.1.2.9.3.27 mysql.time_zone_name Table

The mysql.time_zone_name table is one of the mysql system tables that can contain time zone information. It is usually preferable for the system to handle the time zone, in which case the table will be empty (the default), but you can populate the mysql time zone tables using the mysql_tzinfo_to_sql utility. See Time Zones for details.

MariaDB starting with 10.4

In MariaDB 10.4 and later, this table uses the Aria storage engine.

MariaDB until 10.3

In MariaDB 10.3 and before, this table uses the MyISAM storage engine.

The mysql.time_zone_name table contains the following fields:

FieldTypeNullKeyDefaultDescription
Namechar(64)NOPRINULLName of the time zone.
Time_zone_idint(10) unsignedNOPRINULLID field, auto_increments.

Example

SELECT * FROM mysql.time_zone_name;
+--------------------+--------------+
| Name               | Time_zone_id |
+--------------------+--------------+
| Africa/Abidjan     |            1 |
| Africa/Accra       |            2 |
| Africa/Addis_Ababa |            3 |
| Africa/Algiers     |            4 |
| Africa/Asmara      |            5 |
| Africa/Asmera      |            6 |
| Africa/Bamako      |            7 |
| Africa/Bangui      |            8 |
| Africa/Banjul      |            9 |
| Africa/Bissau      |           10 |
...
+--------------------+--------------+

See Also

1.1.1.2.9.3.28 mysql.time_zone_transition Table

The mysql.time_zone_transition table is one of the mysql system tables that can contain time zone information. It is usually preferable for the system to handle the time zone, in which case the table will be empty (the default), but you can populate the mysql time zone tables using the mysql_tzinfo_to_sql utility. See Time Zones for details.

MariaDB starting with 10.4

In MariaDB 10.4 and later, this table uses the Aria storage engine.

MariaDB until 10.3

In MariaDB 10.3 and before, this table uses the MyISAM storage engine.

The mysql.time_zone_transition table contains the following fields:

FieldTypeNullKeyDefaultDescription
Time_zone_idint(10) unsignedNOPRINULL
Transition_timebigint(20)NOPRINULL
Transition_type_idint(10) unsignedNONULL

Example

SELECT * FROM mysql.time_zone_transition;
+--------------+-----------------+--------------------+
| Time_zone_id | Transition_time | Transition_type_id |
+--------------+-----------------+--------------------+
|            1 |     -1830383032 |                  1 |
|            2 |     -1640995148 |                  2 |
|            2 |     -1556841600 |                  1 |
|            2 |     -1546388400 |                  2 |
|            2 |     -1525305600 |                  1 |
|            2 |     -1514852400 |                  2 |
|            2 |     -1493769600 |                  1 |
|            2 |     -1483316400 |                  2 |
|            2 |     -1462233600 |                  1 |
|            2 |     -1451780400 |                  2 |
...
+--------------+-----------------+--------------------+

See Also

1.1.1.2.9.3.29 mysql.time_zone_transition_type Table

The mysql.time_zone_transition_type table is one of the mysql system tables that can contain time zone information. It is usually preferable for the system to handle the time zone, in which case the table will be empty (the default), but you can populate the mysql time zone tables using the mysql_tzinfo_to_sql utility. See Time Zones for details.

MariaDB starting with 10.4

In MariaDB 10.4 and later, this table uses the Aria storage engine.

MariaDB until 10.3

In MariaDB 10.3 and before, this table uses the MyISAM storage engine.

The mysql.time_zone_transition_type table contains the following fields:

FieldTypeNullKeyDefaultDescription
Time_zone_idint(10) unsignedNOPRINULL
Transition_type_idint(10) unsignedNOPRINULL
Offsetint(11)NO0
Is_DSTtinyint(3) unsignedNO0
Abbreviationchar(8)NO

Example

SELECT * FROM mysql.time_zone_transition_type;
+--------------+--------------------+--------+--------+--------------+
| Time_zone_id | Transition_type_id | Offset | Is_DST | Abbreviation |
+--------------+--------------------+--------+--------+--------------+
|            1 |                  0 |   -968 |      0 | LMT          |
|            1 |                  1 |      0 |      0 | GMT          |
|            2 |                  0 |    -52 |      0 | LMT          |
|            2 |                  1 |   1200 |      1 | GHST         |
|            2 |                  2 |      0 |      0 | GMT          |
|            3 |                  0 |   8836 |      0 | LMT          |
|            3 |                  1 |  10800 |      0 | EAT          |
|            3 |                  2 |   9000 |      0 | BEAT         |
|            3 |                  3 |   9900 |      0 | BEAUT        |
|            3 |                  4 |  10800 |      0 | EAT          |
...
+--------------+--------------------+--------+--------+--------------+

See Also

1.1.1.2.9.3.30 mysql.transaction_registry Table

MariaDB starting with 10.3.4

The mysql.transaction_registry table was introduced in MariaDB 10.3.4 as part of system-versioned tables.

The mysql.transaction_registry table is used for transaction-precise versioning, and contains the following fields:

FieldTypeNullKeyDefaultDescription
transaction_idbigint(20) unsignedNOPrimaryNULL
commit_idbigint(20) unsignedNOUniqueNULL
begin_timestamptimestamp(6)NOMultiple0000-00-00 00:00:00.000000Timestamp when the transaction began (BEGIN statement), however see MDEV-16024.
committimestamp(6)NOMultiple0000-00-00 00:00:00.000000Timestamp when the transaction was committed.
isolation_levelenum('READ-UNCOMMITTED','READ-COMMITTED','REPEATABLE-READ','SERIALIZABLE')NONULLTransaction isolation level.

1.1.1.2.9.3.31 mysql.user Table

The mysql.user table contains information about users that have permission to access the MariaDB server, and their global privileges. The table can be queried and although it is possible to directly update it, it is best to use GRANT and CREATE USER for adding users and privileges.

Note that the MariaDB privileges occur at many levels. A user may not be granted create privilege at the user level, but may still have create permission on certain tables or databases, for example. See privileges for a more complete view of the MariaDB privilege system.

MariaDB until 10.3

In MariaDB 10.3 and before, this table uses the MyISAM storage engine.

MariaDB starting with 10.4

In MariaDB 10.4 and later, the mysql.global_priv table has replaced the mysql.user table, and mysql.user should be considered obsolete. It is now a view into mysql.global_priv created for compatibility with older applications and monitoring scripts. New tools are supposed to use INFORMATION_SCHEMA tables. From MariaDB 10.4.13, the dedicated mariadb.sys user is created as the definer of the view. Previously, root was the definer, which resulted in privilege problems when this username was changed (MDEV-19650).

The mysql.user table contains the following fields:

FieldTypeNullKeyDefaultDescriptionIntroduced
Hostchar(60)NOPRIHost (together with User makes up the unique identifier for this account.
Userchar(80)NOPRIUser (together with Host makes up the unique identifier for this account.
Passwordlongtext (>= MariaDB 10.4.1), char(41) (<= MariaDB 10.4.0)NOHashed password, generated by the PASSWORD() function.
Select_privenum('N','Y')NONCan perform SELECT statements.
Insert_privenum('N','Y')NONCan perform INSERT statements.
Update_privenum('N','Y')NONCan perform UPDATE statements.
Delete_privenum('N','Y')NONCan perform DELETE statements.
Create_privenum('N','Y')NONCan CREATE DATABASE's or CREATE TABLE's.
Drop_privenum('N','Y')NONCan DROP DATABASE's or DROP TABLE's.
Reload_privenum('N','Y')NONCan execute FLUSH statements or equivalent mysqladmin commands.
Shutdown_privenum('N','Y')NONCan shut down the server with SHUTDOWN or mysqladmin shutdown.
Process_privenum('N','Y')NONCan show information about active processes, via SHOW PROCESSLIST or mysqladmin processlist.
File_privenum('N','Y')NONRead and write files on the server, using statements like LOAD DATA INFILE or functions like LOAD_FILE(). Also needed to create CONNECT outward tables. MariaDB server must have permission to access those files.
Grant_privenum('N','Y')NONUser can grant privileges they possess.
References_privenum('N','Y')NONUnused
Index_privenum('N','Y')NONCan create an index on a table using the CREATE INDEX statement. Without the INDEX privilege, user can still create indexes when creating a table using the CREATE TABLE statement if the user has have the CREATE privilege, and user can create indexes using the ALTER TABLE statement if they have the ALTER privilege.
Alter_privenum('N','Y')NONCan perform ALTER TABLE statements.
Show_db_privenum('N','Y')NONCan list all databases using the SHOW DATABASES statement. Without the SHOW DATABASES privilege, user can still issue the SHOW DATABASES statement, but it will only list databases containing tables on which they have privileges.
Super_privenum('N','Y')NONCan execute superuser statements: CHANGE MASTER TO, KILL (users who do not have this privilege can only KILL their own threads), PURGE LOGS, SET global system variables, or the mysqladmin debug command. Also, this permission allows the user to write data even if the read_only startup option is set, enable or disable logging, enable or disable replication on slaves, specify a DEFINER for statements that support that clause, connect once after reaching the MAX_CONNECTIONS. If a statement has been specified for the init-connect mysqld option, that command will not be executed when a user with SUPER privileges connects to the server.
Create_tmp_table_privenum('N','Y')NONCan create temporary tables with the CREATE TEMPORARY TABLE statement.
Lock_tables_privenum('N','Y')NONAcquire explicit locks using the LOCK TABLES statement; user also needs to have the SELECT privilege on a table in order to lock it.
Execute_privenum('N','Y')NONCan execute stored procedure or functions.
Repl_slave_privenum('N','Y')NONAccounts used by slave servers on the master need this privilege. This is needed to get the updates made on the master.
Repl_client_privenum('N','Y')NONCan execute SHOW MASTER STATUS and SHOW SLAVE STATUS statements.
Create_view_privenum('N','Y')NONCan create a view using the CREATE_VIEW statement.
Show_view_privenum('N','Y')NONCan show the CREATE VIEW statement to create a view using the SHOW CREATE VIEW statement.
Create_routine_privenum('N','Y')NONCan create stored programs using the CREATE PROCEDURE and CREATE FUNCTION statements.
Alter_routine_privenum('N','Y')NONCan change the characteristics of a stored function using the ALTER FUNCTION statement.
Create_user_privenum('N','Y')NONCan create a user using the CREATE USER statement, or implicitly create a user with the GRANT statement.
Event_privenum('N','Y')NONCreate, drop and alter events.
Trigger_privenum('N','Y')NONCan execute triggers associated with tables the user updates, execute the CREATE TRIGGER and DROP TRIGGER statements.
Create_tablespace_privenum('N','Y')NON
Delete_history_privenum('N','Y')NONCan delete rows created through system versioning.MariaDB 10.3.5
ssl_typeenum('', 'ANY', 'X509', 'SPECIFIED')NOTLS type - see TLS options.
ssl_cipherblobNONULLTLS cipher - see TLS options.
x509_issuerblobNONULLX509 cipher - see TLS options.
x509_subjectblobNONULLSSL subject - see TLS options.
max_questionsint(11) unsignedNO0Number of queries the user can perform per hour. Zero is unlimited. See per-account resource limits.
max_updatesint(11) unsignedNO0Number of updates the user can perform per hour. Zero is unlimited. See per-account resource limits.
max_connectionsint(11) unsignedNO0Number of connections the account can start per hour. Zero is unlimited. See per-account resource limits.
max_user_connectionsint(11)NO0Number of simultaneous connections the account can have. Zero is unlimited. See per-account resource limits.
pluginchar(64)NOAuthentication plugin used on connection. If empty, uses the default.MariaDB 5.5
authentication_stringtextNONULLAuthentication string for the authentication plugin.MariaDB 5.5
password_expiredenum('N','Y')NONMySQL-compatibility option, not implemented in MariaDB.
is_roleenum('N','Y')NONWhether the user is a role.MariaDB 10.0.5
default_rolechar(80)NONRole which will be enabled on user login automatically.MariaDB 10.1.1
max_statement_timedecimal(12,6)NO0.000000If non-zero, how long queries can run before being killed automatically.MariaDB 10.1.1
FieldTypeNullKeyDefaultDescriptionIntroduced

The Acl_roles status variable, added in MariaDB 10.1.4, indicates how many rows the mysql.user table contains where is_role='Y'.

The Acl_users status variable, added in MariaDB 10.1.4, indicates how many rows the mysql.user table contains where is_role='N'.

Authentication Plugin

When the plugin column is empty, MariaDB defaults to authenticating accounts with either the mysql_native_password or the mysql_old_password plugins. It decides which based on the hash used in the value for the Password column. When there's no password set or when the 4.1 password hash is used, (which is 41 characters long), MariaDB uses the mysql_native_password plugin. The mysql_old_password plugin is used with pre-4.1 password hashes, (which are 16 characters long).

MariaDB also supports the use of alternative authentication plugins. When the plugin column is not empty for the given account, MariaDB uses it to authenticate connection attempts. The specific plugin then uses the value of either the Password column or the authentication_string column to authenticate the user.

A specific authentication plugin can be used for an account by providing the IDENTIFIED VIA authentication_plugin clause with the CREATE USER, ALTER USER, or GRANT statements.

For example, the following statement would create an account that authenticates with the PAM authentication plugin:

CREATE USER foo2@test IDENTIFIED VIA pam;

If the specific authentication plugin uses the authentication_string column, then this value for the account can be specified after a USING or AS keyword. For example, the PAM authentication plugin accepts a service name that would go into the authentication_string column for the account:

CREATE USER foo2@test IDENTIFIED VIA pam USING 'mariadb';

1.1.1.2.9.3.32 Spider mysql Database Tables

The Spider storage engine installs the following system tables in the mysql database.

1.1.1.2.9.3.32.1 mysql.spider_link_failed_log Table

The mysql.spider_link_failed_log table is installed by the Spider storage engine.

MariaDB starting with 10.4

In MariaDB 10.4 and later, this table uses the Aria storage engine.

MariaDB until 10.3

In MariaDB 10.3 and before, this table uses the MyISAM storage engine.

It contains the following fields:

FieldTypeNullKeyDefaultDescription
db_namechar(64)NO
table_namechar(199)NO
link_idchar(64)NO
failed_timetimestampNOcurrent_timestamp()

1.1.1.2.9.3.32.2 mysql.spider_link_mon_servers Table

The mysql.spider_link_mon_servers table is installed by the Spider storage engine.

MariaDB starting with 10.4

In MariaDB 10.4 and later, this table uses the Aria storage engine.

MariaDB until 10.3

In MariaDB 10.3 and before, this table uses the MyISAM storage engine.

It contains the following fields:

FieldTypeNullKeyDefaultDescription
db_namechar(64)NOPRI
table_namechar(199)NOPRI
link_idchar(64)NOPRI
sidint(10) unsignedNOPRI0
serverchar(64)YESNULL
schemechar(64)YESNULL
hostchar(64)YESNULL
portchar(5)YESNULL
sockettextYESNULL
usernamechar(64)YESNULL
passwordchar(64)YESNULL
ssl_catextYESNULL
ssl_capathtextYESNULL
ssl_certtextYESNULL
ssl_cipherchar(64)YESNULL
ssl_keytextYESNULL
ssl_verify_server_certtinyint(4)NO0
default_filetextYESNULL
default_groupchar(64)YESNULL
dsnchar(64)YESNULL
filedsntextYESNULL
driverchar(64)YESNULL

1.1.1.2.9.3.32.3 mysql.spider_tables Table

The mysql.spider_tables table is installed by the Spider storage engine.

MariaDB starting with 10.4

In MariaDB 10.4 and later, this table uses the Aria storage engine.

MariaDB until 10.3

In MariaDB 10.3 and before, this table uses the MyISAM storage engine.

It contains the following fields:

FieldTypeNullKeyDefaultDescription
db_namechar(64)NOPRI
table_namechar(199)NOPRI
link_idint(11)NOPRI0
prioritybigint(20)NOMUL0
serverchar(64)YESNULL
schemechar(64)YESNULL
hostchar(64)YESNULL
portchar(5)YESNULL
sockettextYESNULL
usernamechar(64)YESNULL
passwordchar(64)YESNULL
ssl_catextYESNULL
ssl_capathtextYESNULL
ssl_certtextYESNULL
ssl_cipherchar(64)YESNULL
ssl_keytextYESNULL
ssl_verify_server_certtinyint(4)NO0
monitoring_binlog_pos_at_failingtinyint(4)NO0
default_filetextYESNULL
default_groupchar(64)YESNULL
dsnchar(64)YESNULL
filedsntextYESNULL
driverchar(64)YESNULL
tgt_db_namechar(64)YESNULL
tgt_table_namechar(64)YESNULL
link_statustinyint(4)NO1
block_statustinyint(4)NO0
static_link_idchar(64)YESNULL

1.1.1.2.9.3.32.4 mysql.spider_table_crd Table

The mysql.spider_table_crd table is installed by the Spider storage engine.

MariaDB starting with 10.4

In MariaDB 10.4 and later, this table uses the Aria storage engine.

MariaDB until 10.3

In MariaDB 10.3 and before, this table uses the MyISAM storage engine.

It contains the following fields:

FieldTypeNullKeyDefaultDescription
db_namechar(64)NOPRI
table_namechar(199)NOPRI
key_seqint(10) unsignedNOPRI0
cardinalitybigint(20)NO0

1.1.1.2.9.3.32.5 mysql.spider_table_position_for_recovery Table

The mysql.spider_table_position_for_recovery table is installed by the Spider storage engine.

MariaDB starting with 10.4

In MariaDB 10.4 and later, this table uses the Aria storage engine.

MariaDB until 10.3

In MariaDB 10.3 and before, this table uses the MyISAM storage engine.

It contains the following fields:

FieldTypeNullKeyDefaultDescription
db_namechar(64)NOPRI
table_namechar(199)NOPRI
failed_link_idint(11)NOPRI0
source_link_idint(11)NOPRI0
filetextYESNULL
positiontextYESNULL
gtidtextYESNULL

1.1.1.2.9.3.32.6 mysql.spider_table_sts Table

The mysql.spider_table_sts table is installed by the Spider storage engine.

MariaDB starting with 10.4

In MariaDB 10.4 and later, this table uses the Aria storage engine.

MariaDB until 10.3

In MariaDB 10.3 and before, this table uses the MyISAM storage engine.

It contains the following fields:

FieldTypeNullKeyDefaultDescription
db_namechar(64)NOPRI
table_namechar(199)NOPRI
data_file_lengthbigint(20) unsignedNO0
max_data_file_lengthbigint(20) unsignedNO0
index_file_lengthbigint(20) unsignedNO0
recordsbigint(20) unsignedNO0
mean_rec_lengthbigint(20) unsignedNO0
check_timedatetimeNO0000-00-00 00:00:00
create_timedatetimeNO0000-00-00 00:00:00
update_timedatetimeNO0000-00-00 00:00:00
checksumbigint(20) unsignedYESNULL

1.1.1.2.9.3.32.7 mysql.spider_xa Table

The mysql.spider_xa table is installed by the Spider storage engine.

MariaDB starting with 10.4

In MariaDB 10.4 and later, this table uses the Aria storage engine.

MariaDB until 10.3

In MariaDB 10.3 and before, this table uses the MyISAM storage engine.

It contains the following fields:

FieldTypeNullKeyDefaultDescription
format_idint(11)NOPRI0
gtrid_lengthint(11)NOPRI0
bqual_lengthint(11)NO0
databinary(128)NOPRI
statuschar(8)NOMUL

1.1.1.2.9.3.32.8 mysql.spider_xa_failed_log Table

The mysql.spider_xa_failed_log table is installed by the Spider storage engine.

MariaDB starting with 10.4

In MariaDB 10.4 and later, this table uses the Aria storage engine.

MariaDB until 10.3

In MariaDB 10.3 and before, this table uses the MyISAM storage engine.

It contains the following fields:

FieldTypeNullKeyDefaultDescription
format_idint(11)NO0
gtrid_lengthint(11)NO0
bqual_lengthint(11)NO0
databinary(128)NOMUL
schemechar(64)NO
hostchar(64)NO
portchar(5)NO
sockettextNONULL
usernamechar(64)NO
passwordchar(64)NO
ssl_catextYESNULL
ssl_capathtextYESNULL
ssl_certtextYESNULL
ssl_cipherchar(64)YESNULL
ssl_keytextYESNULL
ssl_verify_server_certtinyint(4)NO0
default_filetextYESNULL
default_groupchar(64)YESNULL
dsnchar(64)YESNULL
filedsntextYESNULL
driverchar(64)YESNULL
thread_idint(11)YESNULL
statuschar(8)NO
failed_timetimestampNOcurrent_timestamp()

1.1.1.2.9.3.32.9 mysql.spider_xa_member Table

The mysql.spider_xa_member table is installed by the Spider storage engine.

MariaDB starting with 10.4

In MariaDB 10.4 and later, this table uses the Aria storage engine.

MariaDB until 10.3

In MariaDB 10.3 and before, this table uses the MyISAM storage engine.

It contains the following fields:

FieldTypeNullKeyDefaultDescription
format_idint(11)NO0
gtrid_lengthint(11)NO0
bqual_lengthint(11)NO0
databinary(128)NOMUL
schemechar(64)NO
hostchar(64)NO
portchar(5)NO
sockettextNONULL
usernamechar(64)NO
passwordchar(64)NO
ssl_catextYESNULL
ssl_capathtextYESNULL
ssl_certtextYESNULL
ssl_cipherchar(64)YESNULL
ssl_keytextYESNULL
ssl_verify_server_certtinyint(4)NO0
default_filetextYESNULL
default_groupchar(64)YESNULL
dsnchar(64)YESNULL
filedsntextYESNULL
driverchar(64)YESNULL

1.1.1.2.9.4 Sys Schema

MariaDB starting with 10.6.0

The sys_schema is a collection of views, functions and procedures to help administrators get insight into database usage.

This article is currently incomplete.

1.1.1.2.9.4.1 Sys Schema sys_config Table

MariaDB starting with 10.6.0

The Sys Schema sys_config table was added in MariaDB 10.6.0.

The sys_config table holds configuration options for the Sys Schema.

This is a persistent table (using the InnoDB storage engine), with the configuration persisting across upgrades (new options are added with INSERT IGNORE).

The table also has two related triggers, which maintain the user that INSERTs or UPDATEs the configuration - sys_config_insert_set_user and sys_config_update_set_user respectively.

Its structure is as follows:

+----------+--------------+------+-----+-------------------+-----------------------------+
| Field    | Type         | Null | Key | Default           | Extra                       |
+----------+--------------+------+-----+-------------------+-----------------------------+
| variable | varchar(128) | NO   | PRI | NULL              |                             |
| value    | varchar(128) | YES  |     | NULL              |                             |
| set_time | timestamp    | NO   |     | CURRENT_TIMESTAMP | on update CURRENT_TIMESTAMP |
| set_by   | varchar(128) | YES  |     | NULL              |                             |
+----------+--------------+------+-----+-------------------+-----------------------------+

Note, when functions check for configuration options, they first check whether a similar named user variable exists with a value, and if this is not set then pull the configuration option from this table in to that named user variable. This is done for performance reasons (to not continually SELECT from the table), however this comes with the side effect that once inited, the values last with the session, somewhat like how session variables are inited from global variables. If the values within this table are changed, they will not take effect until the user logs in again.

Options Included

VariableDefault ValueDescription
statement_truncate_len64Sets the size to truncate statements to, for the format_statement function.
statement_performance_analyzer.limit100The maximum number of rows to include for the views that does not have a built-in limit (e.g. the 95th percentile view). If not set the limit is 100.
statement_performance_analyzer.viewNULLUsed together with the 'custom' view. If the value contains a space, it is considered a query, otherwise it must be an existing view querying the performance_schema.events_statements_summary_by_digest table.
diagnostics.allow_i_s_tablesOFFSpecifies whether it is allowed to do table scan queries on information_schema.TABLES for the diagnostics procedure.
diagnostics.include_rawOFFSet to 'ON' to include the raw data (e.g. the original output of "SELECT * FROM sys.metrics") for the diagnostics procedure.
ps_thread_trx_info.max_length65535Sets the maximum output length for JSON object output by the ps_thread_trx_info() function.

1.1.1.2.9.4.2 Sys Schema Stored Functions

This article is currently incomplete.

The following stored functions are available in the Sys Schema.

1.1.1.2.9.4.2.1 extract_schema_from_file_name

Syntax

sys.extract_schema_from_file_name(path)

Description

extract_schema_from_file_name is a stored function available with the Sys Schema.

Given a file path, it returns the schema (database) name. The file name is assumed to be within the schema directory, and therefore the function will not return the expected result with partitions, or when tables are defined using the DATA_DIRECTORY table option.

The function does not examine anything on disk. The return value, a VARCHAR(64), is determined solely from the provided path.

Examples

SELECT sys.extract_schema_from_file_name('/usr/local/mysql/data/db/t1.ibd');
+----------------------------------------------------------------------+
| sys.extract_schema_from_file_name('/usr/local/mysql/data/db/t1.ibd') |
+----------------------------------------------------------------------+
| db                                                                   |
+----------------------------------------------------------------------+

See also

1.1.1.2.9.4.2.2 extract_table_from_file_name

Syntax

sys.extract_table_from_file_name(path)

Description

extract_table_from_file_name is a stored function available with the Sys Schema.

Given a file path, it returns the table name.

The function does not examine anything on disk. The return value, a VARCHAR(64), is determined solely from the provided path.

Examples

SELECT sys.extract_table_from_file_name('/usr/local/mysql/data/db/t1.ibd');
+---------------------------------------------------------------------+
| sys.extract_table_from_file_name('/usr/local/mysql/data/db/t1.ibd') |
+---------------------------------------------------------------------+
| t1                                                                  |
+---------------------------------------------------------------------+

See also

1.1.1.2.9.4.2.3 format_bytes

Syntax

sys.format_bytes(double)

Description

format_bytes is a stored function available with the Sys Schema.

Given a byte count, returns a string consisting of a value and the units in a human-readable format. The units will be in bytes, KiB (kibibytes), MiB (mebibytes), GiB (gibibytes), TiB (tebibytes), or PiB (pebibytes).

The binary prefixes (kibi, mebi, gibi, tebi and pebi) were created in December 1998 by the International Electrotechnical Commission to avoid possible ambiguity, as the widely-used prefixes kilo, mega, giga, tera and peta can be used to refer to both the power-of-10 decimal system multipliers and the power-of-two binary system multipliers.

Examples

SELECT sys.format_bytes(1000),sys.format_bytes(1024);
+------------------------+------------------------+
| sys.format_bytes(1000) | sys.format_bytes(1024) |
+------------------------+------------------------+
| 1000 bytes             | 1.00 KiB               |
+------------------------+------------------------+

SELECT sys.format_bytes(1000000),sys.format_bytes(1048576);
+---------------------------+---------------------------+
| sys.format_bytes(1000000) | sys.format_bytes(1048576) |
+---------------------------+---------------------------+
| 976.56 KiB                | 1.00 MiB                  |
+---------------------------+---------------------------+

SELECT sys.format_bytes(1000000000),sys.format_bytes(1073741874);
+------------------------------+------------------------------+
| sys.format_bytes(1000000000) | sys.format_bytes(1073741874) |
+------------------------------+------------------------------+
| 953.67 MiB                   | 1.00 GiB                     |
+------------------------------+------------------------------+

SELECT sys.format_bytes(1000000000000),sys.format_bytes(1099511627776);
+---------------------------------+---------------------------------+
| sys.format_bytes(1000000000000) | sys.format_bytes(1099511627776) |
+---------------------------------+---------------------------------+
| 931.32 GiB                      | 1.00 TiB                        |
+---------------------------------+---------------------------------+

SELECT sys.format_bytes(1000000000000000),sys.format_bytes(1125899906842624);
+------------------------------------+------------------------------------+
| sys.format_bytes(1000000000000000) | sys.format_bytes(1125899906842624) |
+------------------------------------+------------------------------------+
| 909.49 TiB                         | 1.00 PiB                           |
+------------------------------------+------------------------------------+

1.1.1.2.9.4.2.4 format_path

Syntax

sys.format_path(path)

Description

format_path is a stored function available with the Sys Schema that, given a path, returns a modified path after replacing subpaths matching the values of various system variables with the variable name.

The system variables that are matched are, in order:

Examples

SELECT @@tmpdir;
+------------------------------------+
| @@tmpdir                           |
+------------------------------------+
| /home/ian/sandboxes/msb_10_8_2/tmp |
+------------------------------------+

SELECT sys.format_path('/home/ian/sandboxes/msb_10_8_2/tmp/testdb.ibd');
+------------------------------------------------------------------+
| sys.format_path('/home/ian/sandboxes/msb_10_8_2/tmp/testdb.ibd') |
+------------------------------------------------------------------+
| @@tmpdir/testdb.ibd                                              |
+------------------------------------------------------------------+

1.1.1.2.9.4.2.5 format_statement

Syntax

sys.format_statement(statement)

Description

Returns a reduced length string. The length is specified by the statement_truncate_len configuration option (default 64), and the removed part of the string (if any) is replaced with an ellipsis (three dots).

The function is intended for use in formatting lengthy SQL statements to a fixed length.

Examples

Default truncation length 64:

SELECT sys.format_statement(
  'SELECT field1, field2, field3, field4, field5, field6 FROM table1'
  ) AS formatted_statement;
+-------------------------------------------------------------------+
| formatted_statement                                               |
+-------------------------------------------------------------------+
| SELECT field1, field2, field3, ... d4, field5, field6 FROM table1 |
+-------------------------------------------------------------------+

Reducing the truncation length to 48:

SET @sys.statement_truncate_len = 48;

SELECT sys.format_statement( 
  'SELECT field1, field2, field3, field4, field5, field6 FROM table1'
  ) AS formatted_statement;
+---------------------------------------------------+
| formatted_statement                               |
+---------------------------------------------------+
| SELECT field1, field2, ... d5, field6 FROM table1 |
+---------------------------------------------------+

1.1.1.2.9.4.2.6 list_add

Syntax

sys.list_add(list,value)

Description

list_add is a stored function available with the Sys Schema.

It takes a list to be be modified and a value to be added to the list, returning the resulting value. This can be used, for example, to add a value to a system variable taking a comma-delimited list of options, such as sql_mode.

The related function list_drop can be used to drop a value from a list.

Examples

SELECT @@sql_mode;
+-----------------------------------------------------------------------+
| @@sql_mode                                                            |
+-----------------------------------------------------------------------+
| STRICT_TRANS_TABLES,ERROR_FOR_DIVISION_BY_ZERO,
NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION |
+-----------------------------------------------------------------------+

SET @@sql_mode = sys.list_add(@@sql_mode, 'NO_ZERO_DATE');

SELECT @@sql_mode;
+-----------------------------------------------------------------------+
| @@sql_mode                                                            |
+-----------------------------------------------------------------------+
| STRICT_TRANS_TABLES,NO_ZERO_DATE,ERROR_FOR_DIVISION_BY_ZERO,
NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION |
+-----------------------------------------------------------------------+

See Also

1.1.1.2.9.4.2.7 list_drop

Syntax

sys.list_drop(list,value)

Description

list_drop is a stored function available with the Sys Schema.

It takes a list to be be modified and a value to be dropped from the list, returning the resulting value. This can be used, for example, to remove a value from a system variable taking a comma-delimited list of options, such as sql_mode.

The related function list_add can be used to add a value to a list.

Examples

SELECT @@sql_mode;
+-----------------------------------------------------------------------+
| @@sql_mode                                                            |
+-----------------------------------------------------------------------+
| STRICT_TRANS_TABLES,ERROR_FOR_DIVISION_BY_ZERO,
NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION |
+-----------------------------------------------------------------------+

SET @@sql_mode = sys.list_drop(@@sql_mode, 'NO_ENGINE_SUBSTITUTION');

SELECT @@sql_mode;
+-----------------------------------------------------------------------+
| @@sql_mode                                                            |
+-----------------------------------------------------------------------+
| STRICT_TRANS_TABLES,ERROR_FOR_DIVISION_BY_ZERO,
NO_AUTO_CREATE_USER |
+-----------------------------------------------------------------------+

See Also

1.1.1.2.9.4.2.8 ps_is_account_enabled

Syntax

sys.ps_is_account_enabled(host,user)

Description

ps_is_account_enabled is a stored function available with the Sys Schema.

It takes host and user arguments, and returns an ENUM('YES','NO') depending on whether Performance Schema instrumentation for the given account is enabled.

Examples

SELECT sys.ps_is_account_enabled('localhost', 'root');
+------------------------------------------------+
| sys.ps_is_account_enabled('localhost', 'root') |
+------------------------------------------------+
| YES                                            |
+------------------------------------------------+

1.1.1.2.9.4.2.9 ps_is_consumer_enabled

Syntax

sys.ps_is_consumer_enabled(consumer)

Description

ps_is_consumer_enabled is a stored function available with the Sys Schema.

It returns an ENUM('YES','NO') depending on whether Performance Schema instrumentation for the given consumer is enabled, and NULL if not given a valid consumer name.

Examples

SELECT sys.ps_is_consumer_enabled('global_instrumentation');
+------------------------------------------------------+
| sys.ps_is_consumer_enabled('global_instrumentation') |
+------------------------------------------------------+
| YES                                                  |
+------------------------------------------------------+

SELECT sys.ps_is_consumer_enabled('events_stages_current');
+-----------------------------------------------------+
| sys.ps_is_consumer_enabled('events_stages_current') |
+-----------------------------------------------------+
| NO                                                  |
+-----------------------------------------------------+

SELECT sys.ps_is_consumer_enabled('nonexistent_consumer');
+----------------------------------------------------+
| sys.ps_is_consumer_enabled('nonexistent_consumer') |
+----------------------------------------------------+
| NULL                                               |
+----------------------------------------------------+

See Also

1.1.1.2.9.4.2.10 ps_is_instrument_default_enabled

Syntax

sys.ps_is_instrument_default_enabled(instrument)

Description

ps_is_instrument_default_enabled is a stored function available with the Sys Schema.

It returns YES if the given Performance Schema instrument is enabled by default, and NO if it is not, does not exist, or is a NULL value.

Examples

SELECT sys.ps_is_instrument_default_enabled('statement/sql/select');
+--------------------------------------------------------------+
| sys.ps_is_instrument_default_enabled('statement/sql/select') |
+--------------------------------------------------------------+
| YES                                                          |
+--------------------------------------------------------------+

SELECT sys.ps_is_instrument_default_enabled('memory/sql/udf_mem');
+------------------------------------------------------------+
| sys.ps_is_instrument_default_enabled('memory/sql/udf_mem') |
+------------------------------------------------------------+
| NO                                                         |
+------------------------------------------------------------+

SELECT sys.ps_is_instrument_default_enabled('memory/sql/nonexistent');
+----------------------------------------------------------------+
| sys.ps_is_instrument_default_enabled('memory/sql/nonexistent') |
+----------------------------------------------------------------+
| NO                                                             |
+----------------------------------------------------------------+

SELECT sys.ps_is_instrument_default_enabled(NULL);
+--------------------------------------------+
| sys.ps_is_instrument_default_enabled(NULL) |
+--------------------------------------------+
| NO                                         |
+--------------------------------------------+

1.1.1.2.9.4.2.11 ps_is_instrument_default_timed

Syntax

sys.ps_is_instrument_default_timed(instrument)

Description

ps_is_instrument_default_timed is a stored function available with the Sys Schema.

It returns YES if the given Performance Schema instrument is timed by default, and NO if it is not, does not exist, or is a NULL value.

Examples

SELECT sys.ps_is_instrument_default_timed('statement/sql/select');
+------------------------------------------------------------+
| sys.ps_is_instrument_default_timed('statement/sql/select') |
+------------------------------------------------------------+
| YES                                                        |
+------------------------------------------------------------+

SELECT sys.ps_is_instrument_default_timed('memory/sql/udf_mem');
+----------------------------------------------------------+
| sys.ps_is_instrument_default_timed('memory/sql/udf_mem') |
+----------------------------------------------------------+
| NO                                                       |
+----------------------------------------------------------+

SELECT sys.ps_is_instrument_default_timed('memory/sql/nonexistent');
+-------------------------------------------------------------+
| sys.ps_is_instrument_default_timed('memory/sql/udf_memsds') |
+-------------------------------------------------------------+
| NO                                                          |
+-------------------------------------------------------------+

SELECT sys.ps_is_instrument_default_timed(NULL);
+------------------------------------------+
| sys.ps_is_instrument_default_timed(NULL) |
+------------------------------------------+
| NO                                       |
+------------------------------------------+

1.1.1.2.9.4.2.12 ps_is_thread_instrumented

Syntax

sys.ps_is_thread_instrumented(connection_id)

Description

ps_is_thread_instrumented is a stored function available with the Sys Schema that returns whether or not Performance Schema instrumentation for the given connection_id is enabled.

  • YES - instrumentation is enabled
  • NO - instrumentation is not enabled
  • UNKNOWN - the connection ID is unknown
  • NULL - NULL value

Examples

SELECT sys.ps_is_thread_instrumented(CONNECTION_ID());
+------------------------------------------------+
| sys.ps_is_thread_instrumented(CONNECTION_ID()) |
+------------------------------------------------+
| YES                                            |
+------------------------------------------------+

SELECT sys.ps_is_thread_instrumented(2042);
+-------------------------------------+
| sys.ps_is_thread_instrumented(2042) |
+-------------------------------------+
| UNKNOWN                             |
+-------------------------------------+

SELECT sys.ps_is_thread_instrumented(NULL);
+-------------------------------------+
| sys.ps_is_thread_instrumented(NULL) |
+-------------------------------------+
| NULL                                |
+-------------------------------------+

1.1.1.2.9.4.2.13 ps_thread_account

Syntax

sys.ps_thread_account(thread_id)

Description

ps_thread_account is a stored function available with the Sys Schema that returns the account (username@hostname) associated with the given thread_id.

Returns NULL if the thread_id is not found.

Examples

SELECT sys.ps_thread_account(sys.ps_thread_id(CONNECTION_ID()));
+----------------------------------------------------------+
| sys.ps_thread_account(sys.ps_thread_id(CONNECTION_ID())) |
+----------------------------------------------------------+
| msandbox@localhost                                       |
+----------------------------------------------------------+

SELECT sys.ps_thread_account(sys.ps_thread_id(2042));
+-----------------------------------------------+
| sys.ps_thread_account(sys.ps_thread_id(2042)) |
+-----------------------------------------------+
| NULL                                          |
+-----------------------------------------------+

SELECT sys.ps_thread_account(sys.ps_thread_id(NULL));
+-----------------------------------------------+
| sys.ps_thread_account(sys.ps_thread_id(NULL)) |
+-----------------------------------------------+
| msandbox@localhost                            |
+-----------------------------------------------+

1.1.1.2.9.4.2.14 ps_thread_id

Syntax

sys.ps_thread_id(connection_id)

Description

ps_thread_id is a stored function available with the Sys Schema that returns the thread_id associated with the given connection_id. If the connection_id is NULL, returns the thread_id for the current connection.

Examples

SELECT * FROM performance_schema.threads\G
*************************** 13. row ***************************
          THREAD_ID: 13
               NAME: thread/sql/one_connection
               TYPE: FOREGROUND
     PROCESSLIST_ID: 3
   PROCESSLIST_USER: msandbox
   PROCESSLIST_HOST: localhost
     PROCESSLIST_DB: test
PROCESSLIST_COMMAND: Query
   PROCESSLIST_TIME: 0
  PROCESSLIST_STATE: Sending data
   PROCESSLIST_INFO: SELECT * FROM performance_schema.threads
   PARENT_THREAD_ID: 1
               ROLE: NULL
       INSTRUMENTED: YES
            HISTORY: YES
    CONNECTION_TYPE: Socket
       THREAD_OS_ID: 24379


SELECT sys.ps_thread_id(3);
+---------------------+
| sys.ps_thread_id(3) |
+---------------------+
|                  13 |
+---------------------+

SELECT sys.ps_thread_id(NULL);
+------------------------+
| sys.ps_thread_id(NULL) |
+------------------------+
|                     13 |
+------------------------+

1.1.1.2.9.4.2.15 ps_thread_stack

Syntax

sys.ps_thread_stack(thread_id, verbose)

Description

ps_thread_stack is a stored function available with the Sys Schema that, for a given thread_id, returns all statements, stages, and events within the Performance Schema, as a JSON formatted stack.

The boolean verbose argument specifies whether or not to include file:lineno information in the events.

Examples

SELECT sys.ps_thread_stack(13, FALSE) AS thread_stack\G
*************************** 1. row ***************************
thread_stack: {"rankdir": "LR","nodesep": "0.10",
  "stack_created": "2022-03-28 16:01:06",
  "mysql_version": "10.8.2-MariaDB",
  "mysql_user": "msandbox@localhost",
  "events": []}

1.1.1.2.9.4.2.16 quote_identifier

Syntax

sys.quote_identifier(str)

Description

quote_identifier is a stored function available with the Sys Schema.

It quotes a string to produce a result that can be used as an identifier in an SQL statement. The string is returned enclosed by backticks ("`") and with each instance of backtick ("`") doubled. If the argument is NULL, the return value is the word "NULL" without enclosing backticks.

Examples

SELECT sys.quote_identifier("Identifier with spaces");
+------------------------------------------------+
| sys.quote_identifier("Identifier with spaces") |
+------------------------------------------------+
| `Identifier with spaces`                       |
+------------------------------------------------+

SELECT sys.quote_identifier("Identifier` containing `backticks");
+-----------------------------------------------------------+
| sys.quote_identifier("Identifier` containing `backticks") |
+-----------------------------------------------------------+
| `Identifier`` containing ``backticks`                     |
+-----------------------------------------------------------+

1.1.1.2.9.4.2.17 version_major

Syntax

sys.version_major()

Description

version_major is a stored function available with the Sys Schema.

It returns the MariaDB Server major release version.

Examples

SELECT VERSION(),
 sys.version_major() AS major, 
 sys.version_minor() AS minor,
 sys.version_patch() AS patch;
+----------------+-------+-------+-------+
| VERSION()      | major | minor | patch |
+----------------+-------+-------+-------+
| 10.8.2-MariaDB |    10 |     8 |     2 |
+----------------+-------+-------+-------+

See Also

1.1.1.2.9.4.2.18 version_minor

Syntax

sys.version_minor()

Description

version_minor is a stored function available with the Sys Schema.

It returns the MariaDB Server minor release version.

Examples

SELECT VERSION(),
 sys.version_major() AS major, 
 sys.version_minor() AS minor,
 sys.version_patch() AS patch;
+----------------+-------+-------+-------+
| VERSION()      | major | minor | patch |
+----------------+-------+-------+-------+
| 10.8.2-MariaDB |    10 |     8 |     2 |
+----------------+-------+-------+-------+

See Also

1.1.1.2.9.4.2.19 version_patch

Syntax

sys.version_patch()

Description

version_patch is a stored function available with the Sys Schema.

It returns the MariaDB Server patch release version.

Examples

SELECT VERSION(),
 sys.version_major() AS major, 
 sys.version_minor() AS minor,
 sys.version_patch() AS patch;
+----------------+-------+-------+-------+
| VERSION()      | major | minor | patch |
+----------------+-------+-------+-------+
| 10.8.2-MariaDB |    10 |     8 |     2 |
+----------------+-------+-------+-------+

See Also

1.1.1.2.9.5 mariadb_schema

Contents

  1. History

mariadb_schema is a data type qualifier that allows one to create MariaDB native date types in an SQL_MODE that has conflicting data type translations.

mariadb_schema was introduced in MariaDB 10.3.24, MariaDB 10.4.14 and MariaDB 10.5.5.

For example, in SQL_MODE=ORACLE, if one creates a table with the DATE type, it will actually create a DATETIME column to match what an Oracle user is expecting. To be able to create a MariaDB DATE in Oracle mode one would have to use mariadb_schema:

CREATE TABLE t1 (d mariadb_schema.DATE);

mariadb_schema is also shown if one creates a table with DATE in MariaDB native mode and then does a SHOW CREATE TABLE in ORACLE mode:

SET sql_mode=DEFAULT;
CREATE OR REPLACE TABLE t1 (
  d DATE
);
SET SQL_mode=ORACLE;
SHOW CREATE TABLE t1;
+-------+--------------------------------------------------------------+
| Table | Create Table                                                 |
+-------+--------------------------------------------------------------+
| t1    | CREATE TABLE "t1" (
  "d" mariadb_schema.date DEFAULT NULL
) |
+-------+--------------------------------------------------------------+

When the server sees the mariadb_schema qualifier, it disables sql_mode-specific data type translation and interprets the data type literally, so for example mariadb_schema.DATE is interpreted as the traditional MariaDB DATE data type, no matter what the current sql_mode is.

The mariadb_schema prefix is displayed only when the data type name would be ambiguous otherwise. The prefix is displayed together with MariaDB DATE when SHOW CREATE TABLE is executed in SQL_MODE=ORACLE. The prefix is not displayed when SHOW CREATE TABLE is executed in SQL_MODE=DEFAULT, or when a non-ambiguous data type is displayed.

Note, the mariadb_schema prefix can be used with any data type, including non-ambiguous ones:

CREATE OR REPLACE TABLE t1 (a mariadb_schema.INT);
SHOW CREATE TABLE t1;
+-------+--------------------------------------------------+
| Table | Create Table                                     |
+-------+--------------------------------------------------+
| t1    | CREATE TABLE "t1" (
  "a" int(11) DEFAULT NULL
) |
+-------+--------------------------------------------------+

Currently the mariadb_schema prefix is only used in the following case:

History

When running with SQL_MODE=ORACLE, MariaDB server translates the data type DATE to DATETIME, for better Oracle compatibility:

SET SQL_mode=ORACLE;
CREATE OR REPLACE TABLE t1 (
  d DATE
);
SHOW CREATE TABLE t1;
+-------+---------------------------------------------------+
| Table | Create Table                                      |
+-------+---------------------------------------------------+
| t1    | CREATE TABLE "t1" (
  "d" datetime DEFAULT NULL
) |
+-------+---------------------------------------------------+

Notice, DATE was translated to DATETIME.

This translation may cause some ambiguity. Suppose a user creates a table with a column of the traditional MariaDB DATE data type using the default sql_mode, but then switches to SQL_MODE=ORACLE and runs a SHOW CREATE TABLE statement:

SET sql_mode=DEFAULT;
CREATE OR REPLACE TABLE t1 (
  d DATE
);
SET SQL_mode=ORACLE;
SHOW CREATE TABLE t1;

Before mariadb_schema was introduced, the above script displayed:

CREATE TABLE "t1" (
  "d" date DEFAULT NULL
);

which had two problems:

  • It was confusing for the reader: its not clear if it is the traditional MariaDB DATE, or is it Oracle-alike date (which is actually DATETIME);
  • It broke replication and caused data type mismatch on the master and on the slave (see MDEV-19632).

To address this problem, starting from the mentioned versions, MariaDB uses the idea of qualified data types:

SET sql_mode=DEFAULT;
CREATE OR REPLACE TABLE t1 (
  d DATE
);
SET SQL_mode=ORACLE;
SHOW CREATE TABLE t1;
+-------+--------------------------------------------------------------+
| Table | Create Table                                                 |
+-------+--------------------------------------------------------------+
| t1    | CREATE TABLE "t1" (
  "d" mariadb_schema.date DEFAULT NULL
) |
+-------+--------------------------------------------------------------+

1.1.1.2.9.6 Writing Logs Into Tables

By default, all logs are disabled or written into files. The general query log and the slow query log can also be written to special tables in the mysql database. During the startup, entries will always be written into files.

Note that EXPLAIN output will only be recorded if the slow query log is written to a file and not to a table.

To write logs into tables, the log_output server system variable is used. Allowed values are FILE, TABLE and NONE. It is possible to specify multiple values, separated with commas, to write the logs into both tables and files. NONE disables logging and has precedence over the other values.

So, to write logs into tables, one of the following settings can be used:

SET GLOBAL log_output = 'TABLE';
SET GLOBAL log_output = 'FILE,TABLE';

The general log will be written into the general_log table, and the slow query log will be written into the slow_log table. Only a limited set of operations are supported for those special tables. For example, direct DML statements (like INSERT) on those tables will fail with an error similar to the following:

ERROR 1556 (HY000): You can't use locks with log tables.

To flush data to the tables, use FLUSH TABLES instead of FLUSH LOGS.

To empty the contents of the log tables, TRUNCATE TABLE can be used.

The log tables use the CSV storage engine by default. This allows an external program to read the files if needed: normal CSV files are stored in the mysql subdirectory, in the data dir. However that engine is slow because it does not support indexes, so you can convert the tables to MyISAM (but not other storage engines). To do so, first temporarily disable logging:

SET GLOBAL general_log = 'OFF';
ALTER TABLE mysql.general_log ENGINE = MyISAM;
ALTER TABLE mysql.slow_log ENGINE = MyISAM;
SET GLOBAL general_log = @old_log_state;

CHECK TABLE and CHECKSUM TABLE are supported.

CREATE TABLE is supported. ALTER TABLE, RENAME TABLE and DROP TABLE are supported when logging is disabled, but log tables cannot be partitioned.

The contents of the log tables is not logged in the binary log thus cannot be replicated.

1.1.1.2.10 BINLOG

Syntax

BINLOG 'str'

Description

BINLOG is an internal-use statement. It is generated by the mariadb-binlog/mysqlbinlog program as the printable representation of certain events in binary log files. The 'str' value is a base 64-encoded string the that server decodes to determine the data change indicated by the corresponding event. This statement requires the SUPER privilege (<= MariaDB 10.5.1) or theBINLOG REPLAY privilege (>= MariaDB 10.5.2).

See also

1.1.1.2.11 PURGE BINARY LOGS

Syntax

PURGE { BINARY | MASTER } LOGS
    { TO 'log_name' | BEFORE datetime_expr }

Description

The PURGE BINARY LOGS statement deletes all the binary log files listed in the log index file prior to the specified log file name or date. BINARY and MASTER are synonyms. Deleted log files also are removed from the list recorded in the index file, so that the given log file becomes the first in the list.

The datetime expression is in the format 'YYYY-MM-DD hh:mm:ss'.

If a replica is active but has yet to read from a binary log file you attempt to delete, the statement will fail with an error. However, if the replica is not connected and has yet to read from a log file you delete, the file will be deleted, but the replica will be unable to continue replicating once it connects again.

This statement has no effect if the server was not started with the --log-bin option to enable binary logging.

To list the binary log files on the server, use SHOW BINARY LOGS. To see which files they are reading, use SHOW SLAVE STATUS (or SHOW REPLICA STATUS from MariaDB 10.5.1). You can only delete the files that are older than the oldest file that is used by the slaves.

To delete all binary log files, use RESET MASTER. To move to a new log file (for example if you want to remove the current log file), use FLUSH LOGS before you execute PURGE LOGS.

If the expire_logs_days server system variable is not set to 0, the server automatically deletes binary log files after the given number of days. From MariaDB 10.6, the binlog_expire_logs_seconds variable allows more precise control over binlog deletion, and takes precedence if both are non-zero.

Requires the SUPER privilege or, from MariaDB 10.5.2, the BINLOG ADMIN privilege, to run.

Examples

PURGE BINARY LOGS TO 'mariadb-bin.000063';

PURGE BINARY LOGS BEFORE '2013-04-21';

PURGE BINARY LOGS BEFORE '2013-04-22 09:55:22';

See Also

1.1.1.2.12 CACHE INDEX

Syntax

CACHE INDEX                      
  tbl_index_list [, tbl_index_list] ...
  IN key_cache_name                    

tbl_index_list:
  tbl_name [[INDEX|KEY] (index_name[, index_name] ...)]

Description

The CACHE INDEX statement assigns table indexes to a specific key cache. It is used only for MyISAM tables.

A default key cache exists and cannot be destroyed. To create more key caches, the key_buffer_size server system variable.

The associations between tables indexes and key caches are lost on server restart. To recreate them automatically, it is necessary to configure caches in a configuration file and include some CACHE INDEX (and optionally LOAD INDEX) statements in the init file.

Examples

The following statement assigns indexes from the tables t1, t2, and t3 to the key cache named hot_cache:

CACHE INDEX t1, t2, t3 IN hot_cache;
+---------+--------------------+----------+----------+
| Table   | Op                 | Msg_type | Msg_text |
+---------+--------------------+----------+----------+
| test.t1 | assign_to_keycache | status   | OK       |
| test.t2 | assign_to_keycache | status   | OK       |
| test.t3 | assign_to_keycache | status   | OK       |
+---------+--------------------+----------+----------+

Implementation (for MyISAM)

Normally CACHE INDEX should not take a long time to execute. Internally it's implemented the following way:

  • Find the right key cache (under LOCK_global_system_variables)
  • Open the table with a TL_READ_NO_INSERT lock.
  • Flush the original key cache for the given file (under key cache lock)
  • Flush the new key cache for the given file (safety)
  • Move the file to the new key cache (under file share lock)

The only possible long operations are getting the locks for the table and flushing the original key cache, if there were many key blocks for the file in it.

We plan to also add CACHE INDEX for Aria tables if there is a need for this.

1.1.1.2.13 DESCRIBE

Syntax

{DESCRIBE | DESC} tbl_name [col_name | wild]

Contents

  1. Syntax
  2. Description
  3. See Also

Description

DESCRIBE provides information about the columns in a table. It is a shortcut for SHOW COLUMNS FROM. These statements also display information for views.

col_name can be a column name, or a string containing the SQL "%" and "_" wildcard characters to obtain output only for the columns with names matching the string. There is no need to enclose the string within quotes unless it contains spaces or other special characters.

DESCRIBE city;
+------------+----------+------+-----+---------+----------------+
| Field      | Type     | Null | Key | Default | Extra          |
+------------+----------+------+-----+---------+----------------+
| Id         | int(11)  | NO   | PRI | NULL    | auto_increment |
| Name       | char(35) | YES  |     | NULL    |                |
| Country    | char(3)  | NO   | UNI |         |                |
| District   | char(20) | YES  | MUL |         |                |
| Population | int(11)  | YES  |     | NULL    |                |
+------------+----------+------+-----+---------+----------------+

The description for SHOW COLUMNS provides more information about the output columns.

See Also

1.1.1.2.14 EXECUTE Statement

Syntax

EXECUTE stmt_name
    [USING expression[, expression] ...]

Contents

  1. Syntax
  2. Description
  3. Example
  4. See Also
MariaDB starting with 10.2.3

EXECUTE with expression as parameters was introduced in MariaDB 10.2.3. Before that one could only use variables (@var_name) as parameters.

Description

After preparing a statement with PREPARE, you execute it with an EXECUTE statement that refers to the prepared statement name. If the prepared statement contains any parameter markers, you must supply a USING clause that lists user variables containing the values to be bound to the parameters. Parameter values can be supplied only by user variables, and the USING clause must name exactly as many variables as the number of parameter markers in the statement.

You can execute a given prepared statement multiple times, passing different variables to it or setting the variables to different values before each execution.

If the specified statement has not been PREPAREd, an error similar to the following is produced:

ERROR 1243 (HY000): Unknown prepared statement handler (stmt_name) given to EXECUTE

Example

See example in PREPARE.

See Also

1.1.1.2.15 HELP Command

Syntax

HELP search_string

Description

The HELP command can be used in any MariaDB client, such as the mysql command-line client, to get basic syntax help and a short description for most commands and functions.

If you provide an argument to the HELP command, the mysql client uses it as a search string to access server-side help. The proper operation of this command requires that the help tables in the mysql database be initialized with help topic information.

If there is no match for the search string, the search fails. Use HELP contents to see a list of the help categories:

HELP contents
You asked for help about help category: "Contents"
For more information, type 'help <item>', where <item> is one of the following
categories:
   Account Management
   Administration
   Compound Statements
   Data Definition
   Data Manipulation
   Data Types
   Functions
   Functions and Modifiers for Use with GROUP BY
   Geographic Features
   Help Metadata
   Language Structure
   Plugins
   Procedures
   Sequences
   Table Maintenance
   Transactions
   User-Defined Functions
   Utility

If a search string matches multiple items, MariaDB shows a list of matching topics:

HELP drop
Many help items for your request exist.
To make a more specific request, please type 'help <item>',
where <item> is one of the following
topics:
   ALTER TABLE
   DROP DATABASE
   DROP EVENT
   DROP FUNCTION
   DROP FUNCTION UDF
   DROP INDEX
   DROP PACKAGE
   DROP PACKAGE BODY
   DROP PROCEDURE
   DROP ROLE
   DROP SEQUENCE
   DROP SERVER
   DROP TABLE
   DROP TRIGGER
   DROP USER
   DROP VIEW

Then you can enter a topic as the search string to see the help entry for that topic.

The help is provided with the MariaDB server and makes use of four help tables found in the mysql database: help_relation, help_topic, help_category and help_keyword. These tables are populated by the mysql_install_db or fill_help_table.sql scripts which, until MariaDB 10.4.7, contain data generated from an old version of MySQL.

1.1.1.2.16 KILL [CONNECTION | QUERY]

Syntax

KILL [HARD | SOFT] [CONNECTION | QUERY [ID] ] [thread_id | USER user_name | query_id]

Contents

  1. Syntax
  2. Description
  3. See Also

Description

Each connection to mysqld runs in a separate thread. You can see which threads are running with the SHOW PROCESSLIST statement and kill a thread with the KILL thread_id statement. KILL allows the optional CONNECTION or QUERY modifier:

  • KILL CONNECTION is the same as KILL with no modifier: It terminates the connection associated with the given thread or query id.
  • KILL QUERY terminates the statement that the connection thread_id is currently executing, but leaves the connection itself intact.
  • KILL QUERY ID (introduced in MariaDB 10.0.5) terminates the query by query_id, leaving the connection intact.

If a connection is terminated that has an active transaction, the transaction will be rolled back. If only a query is killed, the current transaction will stay active. See also idle_transaction_timeout.

If you have the PROCESS privilege, you can see all threads. If you have the SUPER privilege, or, from MariaDB 10.5.2, the CONNECTION ADMIN privilege, you can kill all threads and statements. Otherwise, you can see and kill only your own threads and statements.

Killing queries that repair or create indexes on MyISAM and Aria tables may result in corrupted tables. Use the SOFT option to avoid this!

The HARD option (default) kills a command as soon as possible. If you use SOFT, then critical operations that may leave a table in an inconsistent state will not be interrupted. Such operations include REPAIR and INDEX creation for MyISAM and Aria tables (REPAIR TABLE, OPTIMIZE TABLE).

KILL ... USER username will kill all connections/queries for a given user. USER can be specified one of the following ways:

If you specify a thread id and that thread does not exist, you get the following error:

ERROR 1094 (HY000): Unknown thread id: <thread_id>

If you specify a query id that doesn't exist, you get the following error:

ERROR 1957 (HY000): Unknown query id: <query_id>

However, if you specify a user name, no error is issued for non-connected (or even non-existing) users. To check if the connection/query has been killed, you can use the ROW_COUNT() function.

A client whose connection is killed receives the following error:

ERROR 1317 (70100): Query execution was interrupted

To obtain a list of existing sessions, use the SHOW PROCESSLIST statement or query the Information Schema PROCESSLIST table.

Note: You cannot use KILL with the Embedded MySQL Server library because the embedded server merely runs inside the threads of the host application. It does not create any connection threads of its own.

Note: You can also use mysqladmin kill thread_id [,thread_id...] to kill connections. To get a list of running queries, use mysqladmin processlist. See mysqladmin.

Percona Toolkit contains a program, pt-kill that can be used to automatically kill connections that match certain criteria. For example, it can be used to terminate idle connections, or connections that have been busy for more than 60 seconds.

See Also

1.1.1.2.17 LOAD INDEX

Syntax

LOAD INDEX INTO CACHE
  tbl_index_list [, tbl_index_list] ...

tbl_index_list:
  tbl_name
    [[INDEX|KEY] (index_name[, index_name] ...)]
    [IGNORE LEAVES]

Description

The LOAD INDEX INTO CACHE statement preloads a table index into the key cache to which it has been assigned by an explicit CACHE INDEX statement, or into the default key cache otherwise. LOAD INDEX INTO CACHE is used only for MyISAM or Aria tables. Until MariaDB 5.3, it was not supported for tables having user-defined partitioning, but this limitation was removed in MariaDB 5.5.

The IGNORE LEAVES modifier causes only blocks for the nonleaf nodes of the index to be preloaded.

1.1.1.2.18 RESET

Syntax

RESET reset_option [, reset_option] ...

Description

The RESET statement is used to clear the state of various server operations. You must have the RELOAD privilege to execute RESET.

RESET acts as a stronger version of the FLUSH statement.

The different RESET options are:

OptionDescription
SLAVE ["connection_name"] [ALL]Deletes all relay logs from the slave and reset the replication position in the master binary log.
MASTERDeletes all old binary logs, makes the binary index file (--log-bin-index) empty and creates a new binary log file. This is useful when you want to reset the master to an initial state. If you want to just delete old, not used binary logs, you should use the PURGE BINARY LOGS command.
QUERY CACHERemoves all queries from the query cache. See also FLUSH QUERY CACHE.

1.1.1.2.19 SHUTDOWN

Contents

  1. Syntax
  2. Description
  3. WAIT FOR ALL SLAVES
  4. Required Permissions
  5. Shutdown for Upgrades
  6. Example
  7. Other Ways to Stop mysqld
  8. See Also

Syntax

SHUTDOWN [WAIT FOR ALL { SLAVES | REPLICAS } ]

Description

The SHUTDOWN command shuts the server down.

WAIT FOR ALL SLAVES

MariaDB starting with 10.4.4

The WAIT FOR ALL SLAVES option was first added in MariaDB 10.4.4. WAIT FOR ALL REPLICAS has been a synonym since MariaDB 10.5.1.

When a master server is shutdown and it goes through the normal shutdown process, the master kills client threads in random order. By default, the master also considers its binary log dump threads to be regular client threads. As a consequence, the binary log dump threads can be killed while client threads still exist, and this means that data can be written on the master during a normal shutdown that won't be replicated. This is true even if semi-synchronous replication is being used.

In MariaDB 10.4 and later, this problem can be solved by shutting down the server with the SHUTDOWN command and by providing the WAIT FOR ALL SLAVES option to the command. For example:

SHUTDOWN WAIT FOR ALL SLAVES;

When the WAIT FOR ALL SLAVES option is provided, the server only kills its binary log dump threads after all client threads have been killed, and it only completes the shutdown after the last binary log has been sent to all connected replicas.

See Replication Threads: Binary Log Dump Threads and the Shutdown Process for more information.

Required Permissions

One must have a SHUTDOWN privilege (see GRANT) to use this command. It is the same privilege one needs to use the mariadb-admin/mysqladmin shutdown command.

Shutdown for Upgrades

If you are doing a shutdown to migrate to another major version of MariaDB, please ensure that the innodb_fast_shutdown variable is not 2 (fast crash shutdown). The default of this variable is 1.

Example

The following example shows how to create an event which turns off the server at a certain time:

CREATE EVENT `test`.`shutd`
    ON SCHEDULE
        EVERY 1 DAY
        STARTS '2014-01-01 20:00:00'
    COMMENT 'Shutdown Maria when the office is closed'
DO BEGIN
    SHUTDOWN;
END;

Other Ways to Stop mysqld

You can use the mariadb-admin/mysqladmin shutdown command to take down mysqld cleanly.

You can also use the system kill command on Unix with signal SIGTERM (15)

kill -SIGTERM pid-of-mysqld-process

You can find the process number of the server process in the file that ends with .pid in your data directory.

The above is identical to mysqladmin shutdown.

On windows you should use:

NET STOP MySQL

See Also

1.1.1.2.20 USE

Syntax

USE db_name

Description

The 'USE db_name' statement tells MariaDB to use the db_name database as the default (current) database for subsequent statements. The database remains the default until the end of the session or another USE statement is issued:

USE db1;
SELECT COUNT(*) FROM mytable;   # selects from db1.mytable
USE db2;
SELECT COUNT(*) FROM mytable;   # selects from db2.mytable

The DATABASE() function (SCHEMA() is a synonym) returns the default database.

Another way to set the default database is specifying its name at mysql command line client startup.

See Also

1.1.1.3 Data Definition

SQL Commands for defining data, such as ALTER, CREATE, DROP, RENAME etc.

There are 3 related questions.

1.1.1.3.1 CREATE

Articles on the various CREATE statements.

There are 1 related questions.

1.1.1.3.1.1 CREATE DATABASE

Syntax

CREATE [OR REPLACE] {DATABASE | SCHEMA} [IF NOT EXISTS] db_name
    [create_specification] ...

create_specification:
    [DEFAULT] CHARACTER SET [=] charset_name
  | [DEFAULT] COLLATE [=] collation_name
  | COMMENT [=] 'comment'

Contents

  1. Syntax
  2. Description
    1. OR REPLACE
    2. IF NOT EXISTS
    3. COMMENT
  3. Examples
  4. See Also

Description

CREATE DATABASE creates a database with the given name. To use this statement, you need the CREATE privilege for the database. CREATE SCHEMA is a synonym for CREATE DATABASE.

For valid identifiers to use as database names, see Identifier Names.

OR REPLACE

MariaDB starting with 10.1.3

The OR REPLACE clause was added in MariaDB 10.1.3

If the optional OR REPLACE clause is used, it acts as a shortcut for:

DROP DATABASE IF EXISTS db_name;
CREATE DATABASE db_name ...;

IF NOT EXISTS

When the IF NOT EXISTS clause is used, MariaDB will return a warning instead of an error if the specified database already exists.

COMMENT

MariaDB starting with 10.5.0

From MariaDB 10.5.0, it is possible to add a comment of a maximum of 1024 bytes. If the comment length exceeds this length, a error/warning code 4144 is thrown. The database comment is also added to the db.opt file, as well as to the information_schema.schemata table.

Examples

CREATE DATABASE db1;
Query OK, 1 row affected (0.18 sec)

CREATE DATABASE db1;
ERROR 1007 (HY000): Can't create database 'db1'; database exists

CREATE OR REPLACE DATABASE db1;
Query OK, 2 rows affected (0.00 sec)

CREATE DATABASE IF NOT EXISTS db1;
Query OK, 1 row affected, 1 warning (0.01 sec)

SHOW WARNINGS;
+-------+------+----------------------------------------------+
| Level | Code | Message                                      |
+-------+------+----------------------------------------------+
| Note  | 1007 | Can't create database 'db1'; database exists |
+-------+------+----------------------------------------------+

Setting the character sets and collation. See Setting Character Sets and Collations for more details.

CREATE DATABASE czech_slovak_names 
  CHARACTER SET = 'keybcs2'
  COLLATE = 'keybcs2_bin';

Comments, from MariaDB 10.5.0:

CREATE DATABASE presentations COMMENT 'Presentations for conferences';

See Also

1.1.1.3.1.2 CREATE EVENT

Syntax

CREATE [OR REPLACE]
    [DEFINER = { user | CURRENT_USER | role | CURRENT_ROLE }]
    EVENT 
    [IF NOT EXISTS]
    event_name    
    ON SCHEDULE schedule
    [ON COMPLETION [NOT] PRESERVE]
    [ENABLE | DISABLE | DISABLE ON SLAVE]
    [COMMENT 'comment']
    DO sql_statement;

schedule:
    AT timestamp [+ INTERVAL interval] ...
  | EVERY interval 
    [STARTS timestamp [+ INTERVAL interval] ...] 
    [ENDS timestamp [+ INTERVAL interval] ...]

interval:
    quantity {YEAR | QUARTER | MONTH | DAY | HOUR | MINUTE |
              WEEK | SECOND | YEAR_MONTH | DAY_HOUR | DAY_MINUTE |
              DAY_SECOND | HOUR_MINUTE | HOUR_SECOND | MINUTE_SECOND}

Contents

  1. Syntax
  2. Description
    1. OR REPLACE
    2. IF NOT EXISTS
    3. ON SCHEDULE
    4. AT
    5. ON COMPLETION [NOT] PRESERVE
    6. ENABLE/DISABLE/DISABLE ON SLAVE
    7. COMMENT
  3. Examples
  4. See Also

Description

This statement creates and schedules a new event. It requires the EVENT privilege for the schema in which the event is to be created.

The minimum requirements for a valid CREATE EVENT statement are as follows:

  • The keywords CREATE EVENT plus an event name, which uniquely identifies the event in the current schema. (Prior to MySQL 5.1.12, the event name needed to be unique only among events created by the same user on a given database.)
  • An ON SCHEDULE clause, which determines when and how often the event executes.
  • A DO clause, which contains the SQL statement to be executed by an event.

Here is an example of a minimal CREATE EVENT statement:

CREATE EVENT myevent
    ON SCHEDULE AT CURRENT_TIMESTAMP + INTERVAL 1 HOUR
    DO
      UPDATE myschema.mytable SET mycol = mycol + 1;

The previous statement creates an event named myevent. This event executes once — one hour following its creation — by running an SQL statement that increments the value of the myschema.mytable table's mycol column by 1.

The event_name must be a valid MariaDB identifier with a maximum length of 64 characters. It may be delimited using back ticks, and may be qualified with the name of a database schema. An event is associated with both a MariaDB user (the definer) and a schema, and its name must be unique among names of events within that schema. In general, the rules governing event names are the same as those for names of stored routines. See Identifier Names.

If no schema is indicated as part of event_name, the default (current) schema is assumed.

For valid identifiers to use as event names, see Identifier Names.

OR REPLACE

The OR REPLACE clause was included in MariaDB 10.1.4. If used and the event already exists, instead of an error being returned, the existing event will be dropped and replaced by the newly defined event.

IF NOT EXISTS

If the IF NOT EXISTS clause is used, MariaDB will return a warning instead of an error if the event already exists. Cannot be used together with OR REPLACE.

ON SCHEDULE

The ON SCHEDULE clause can be used to specify when the event must be triggered.

AT

If you want to execute the event only once (one time event), you can use the AT keyword, followed by a timestamp. If you use CURRENT_TIMESTAMP, the event acts as soon as it is created. As a convenience, you can add one or more intervals to that timestamp. You can also specify a timestamp in the past, so that the event is stored but not triggered, until you modify it via ALTER EVENT.

The following example shows how to create an event that will be triggered tomorrow at a certain time:

CREATE EVENT example
ON SCHEDULE AT CURRENT_TIMESTAMP + INTERVAL 1 DAY + INTERVAL 3 HOUR
DO something;

You can also specify that an event must be triggered at a regular interval (recurring event). In such cases, use the EVERY clause followed by the interval.

If an event is recurring, you can specify when the first execution must happen via the STARTS clause and a maximum time for the last execution via the ENDS clause. STARTS and ENDS clauses are followed by a timestamp and, optionally, one or more intervals. The ENDS clause can specify a timestamp in the past, so that the event is stored but not executed until you modify it via ALTER EVENT.

In the following example, next month a recurring event will be triggered hourly for a week:

CREATE EVENT example
ON SCHEDULE EVERY 1 HOUR
STARTS CURRENT_TIMESTAMP + INTERVAL 1 MONTH
ENDS CURRENT_TIMESTAMP + INTERVAL 1 MONTH + INTERVAL 1 WEEK
DO some_task;

Intervals consist of a quantity and a time unit. The time units are the same used for other staments and time functions, except that you can't use microseconds for events. For simple time units, like HOUR or MINUTE, the quantity is an integer number, for example '10 MINUTE'. For composite time units, like HOUR_MINUTE or HOUR_SECOND, the quantity must be a string with all involved simple values and their separators, for example '2:30' or '2:30:30'.

ON COMPLETION [NOT] PRESERVE

The ON COMPLETION clause can be used to specify if the event must be deleted after its last execution (that is, after its AT or ENDS timestamp is past). By default, events are dropped when they are expired. To explicitly state that this is the desired behaviour, you can use ON COMPLETION NOT PRESERVE. Instead, if you want the event to be preserved, you can use ON COMPLETION PRESERVE.

In you specify ON COMPLETION NOT PRESERVE, and you specify a timestamp in the past for AT or ENDS clause, the event will be immediatly dropped. In such cases, you will get a Note 1558: "Event execution time is in the past and ON COMPLETION NOT PRESERVE is set. The event was dropped immediately after creation".

ENABLE/DISABLE/DISABLE ON SLAVE

Events are ENABLEd by default. If you want to stop MariaDB from executing an event, you may specify DISABLE. When it is ready to be activated, you may enable it using ALTER EVENT. Another option is DISABLE ON SLAVE, which indicates that an event was created on a master and has been replicated to the slave, which is prevented from executing the event. If DISABLE ON SLAVE is specifically set, the event will not be executed.

COMMENT

The COMMENT clause may be used to set a comment for the event. Maximum length for comments is 64 characters. The comment is a string, so it must be quoted. To see events comments, you can query the INFORMATION_SCHEMA.EVENTS table (the column is named EVENT_COMMENT).

Examples

Minimal CREATE EVENT statement:

CREATE EVENT myevent
    ON SCHEDULE AT CURRENT_TIMESTAMP + INTERVAL 1 HOUR
    DO
      UPDATE myschema.mytable SET mycol = mycol + 1;

An event that will be triggered tomorrow at a certain time:

CREATE EVENT example
ON SCHEDULE AT CURRENT_TIMESTAMP + INTERVAL 1 DAY + INTERVAL 3 HOUR
DO something;

Next month a recurring event will be triggered hourly for a week:

CREATE EVENT example
ON SCHEDULE EVERY 1 HOUR
STARTS CURRENT_TIMESTAMP + INTERVAL 1 MONTH
ENDS CURRENT_TIMESTAMP + INTERVAL 1 MONTH + INTERVAL 1 WEEK
DO some_task;

OR REPLACE and IF NOT EXISTS:

CREATE EVENT myevent
    ON SCHEDULE AT CURRENT_TIMESTAMP + INTERVAL 1 HOUR
    DO
      UPDATE myschema.mytable SET mycol = mycol + 1;
ERROR 1537 (HY000): Event 'myevent' already exists

CREATE OR REPLACE EVENT myevent
    ON SCHEDULE AT CURRENT_TIMESTAMP + INTERVAL 1 HOUR
    DO
      UPDATE myschema.mytable SET mycol = mycol + 1;;
Query OK, 0 rows affected (0.00 sec)

CREATE EVENT IF NOT EXISTS myevent
    ON SCHEDULE AT CURRENT_TIMESTAMP + INTERVAL 1 HOUR
    DO
      UPDATE myschema.mytable SET mycol = mycol + 1;
Query OK, 0 rows affected, 1 warning (0.00 sec)

 SHOW WARNINGS;
+-------+------+--------------------------------+
| Level | Code | Message                        |
+-------+------+--------------------------------+
| Note  | 1537 | Event 'myevent' already exists |
+-------+------+--------------------------------+

See Also

1.1.1.3.1.3 CREATE FUNCTION

Syntax

CREATE [OR REPLACE]
    [DEFINER = {user | CURRENT_USER | role | CURRENT_ROLE }]
    [AGGREGATE] FUNCTION [IF NOT EXISTS] func_name ([func_parameter[,...]])
    RETURNS type
    [characteristic ...]
    RETURN func_body


func_parameter:
    [ IN | OUT | INOUT | IN OUT ]  param_name type


type:
    Any valid MariaDB data type


characteristic:
    LANGUAGE SQL
  | [NOT] DETERMINISTIC
  | { CONTAINS SQL | NO SQL | READS SQL DATA | MODIFIES SQL DATA }
  | SQL SECURITY { DEFINER | INVOKER }
  | COMMENT 'string'


func_body:
    Valid SQL procedure statement

Contents

  1. Syntax
  2. Description
    1. IN | OUT | INOUT | IN OUT
    2. AGGREGATE
    3. RETURNS
    4. LANGUAGE SQL
    5. OR REPLACE
    6. IF NOT EXISTS
    7. [NOT] DETERMINISTIC
    8. MODIFIES SQL DATA
    9. READS SQL DATA
    10. CONTAINS SQL
    11. NO SQL
    12. Oracle Mode
  3. Security
  4. Character sets and collations
  5. Examples
  6. See Also

Description

Use the CREATE FUNCTION statement to create a new stored function. You must have the CREATE ROUTINE database privilege to use CREATE FUNCTION. A function takes any number of arguments and returns a value from the function body. The function body can be any valid SQL expression as you would use, for example, in any select expression. If you have the appropriate privileges, you can call the function exactly as you would any built-in function. See Security below for details on privileges.

You can also use a variant of the CREATE FUNCTION statement to install a user-defined function (UDF) defined by a plugin. See CREATE FUNCTION (UDF) for details.

You can use a SELECT statement for the function body by enclosing it in parentheses, exactly as you would to use a subselect for any other expression. The SELECT statement must return a single value. If more than one column is returned when the function is called, error 1241 results. If more than one row is returned when the function is called, error 1242 results. Use a LIMIT clause to ensure only one row is returned.

You can also replace the RETURN clause with a BEGIN...END compound statement. The compound statement must contain a RETURN statement. When the function is called, the RETURN statement immediately returns its result, and any statements after RETURN are effectively ignored.

By default, a function is associated with the current database. To associate the function explicitly with a given database, specify the fully-qualified name as db_name.func_name when you create it. If the function name is the same as the name of a built-in function, you must use the fully qualified name when you call it.

The parameter list enclosed within parentheses must always be present. If there are no parameters, an empty parameter list of () should be used. Parameter names are not case sensitive.

Each parameter can be declared to use any valid data type, except that the COLLATE attribute cannot be used.

For valid identifiers to use as function names, see Identifier Names.

IN | OUT | INOUT | IN OUT

MariaDB starting with 10.8.0

The function parameter qualifiers for IN, OUT, INOUT, and IN OUT were added in a 10.8.0 preview release. Prior to 10.8.0 quantifiers were supported only in procedures.

OUT, INOUT and its equivalent IN OUT, are only valid if called from SET and not SELECT. These quantifiers are especially useful for creating functions with more than one return value. This allows functions to be more complex and nested.

DELIMITER $$
CREATE FUNCTION add_func3(IN a INT, IN b INT, OUT c INT) RETURNS INT
BEGIN
  SET c = 100;
  RETURN a + b;
END;
$$
DELIMITER ;
 
SET @a = 2;
SET @b = 3;
SET @c = 0;
SET @res= add_func3(@a, @b, @c);

SELECT add_func3(@a, @b, @c);
ERROR 4186 (HY000): OUT or INOUT argument 3 for function add_func3 is not allowed here

DELIMITER $$
CREATE FUNCTION add_func4(IN a INT, IN b INT, d INT) RETURNS INT
BEGIN
  DECLARE c, res INT;
  SET res = add_func3(a, b, c) + d;
  if (c > 99) then
    return  3;
  else
    return res;
  end if;
END;
$$

DELIMITER ;

SELECT add_func4(1,2,3);
+------------------+
| add_func4(1,2,3) |
+------------------+
|                3 |
+------------------+

AGGREGATE

MariaDB starting with 10.3.3

From MariaDB 10.3.3, it is possible to create stored aggregate functions as well. See Stored Aggregate Functions for details.

RETURNS

The RETURNS clause specifies the return type of the function. NULL values are permitted with all return types.

What happens if the RETURN clause returns a value of a different type? It depends on the SQL_MODE in effect at the moment of the function creation.

If the SQL_MODE is strict (STRICT_ALL_TABLES or STRICT_TRANS_TABLES flags are specified), a 1366 error will be produced.

Otherwise, the value is coerced to the proper type. For example, if a function specifies an ENUM or SET value in the RETURNS clause, but the RETURN clause returns an integer, the value returned from the function is the string for the corresponding ENUM member of set of SET members.

MariaDB stores the SQL_MODE system variable setting that is in effect at the time a routine is created, and always executes the routine with this setting in force, regardless of the server SQL mode in effect when the routine is invoked.

LANGUAGE SQL

LANGUAGE SQL is a standard SQL clause, and it can be used in MariaDB for portability. However that clause has no meaning, because SQL is the only supported language for stored functions.

A function is deterministic if it can produce only one result for a given list of parameters. If the result may be affected by stored data, server variables, random numbers or any value that is not explicitly passed, then the function is not deterministic. Also, a function is non-deterministic if it uses non-deterministic functions like NOW() or CURRENT_TIMESTAMP(). The optimizer may choose a faster execution plan if it known that the function is deterministic. In such cases, you should declare the routine using the DETERMINISTIC keyword. If you want to explicitly state that the function is not deterministic (which is the default) you can use the NOT DETERMINISTIC keywords.

If you declare a non-deterministic function as DETERMINISTIC, you may get incorrect results. If you declare a deterministic function as NOT DETERMINISTIC, in some cases the queries will be slower.

OR REPLACE

MariaDB starting with 10.1.3

If the optional OR REPLACE clause is used, it acts as a shortcut for:

DROP FUNCTION IF EXISTS function_name;
CREATE FUNCTION function_name ...;

with the exception that any existing privileges for the function are not dropped.

IF NOT EXISTS

MariaDB starting with 10.1.3

If the IF NOT EXISTS clause is used, MariaDB will return a warning instead of an error if the function already exists. Cannot be used together with OR REPLACE.

[NOT] DETERMINISTIC

The [NOT] DETERMINISTIC clause also affects binary logging, because the STATEMENT format can not be used to store or replicate non-deterministic statements.

CONTAINS SQL, NO SQL, READS SQL DATA, and MODIFIES SQL DATA are informative clauses that tell the server what the function does. MariaDB does not check in any way whether the specified clause is correct. If none of these clauses are specified, CONTAINS SQL is used by default.

MODIFIES SQL DATA

MODIFIES SQL DATA means that the function contains statements that may modify data stored in databases. This happens if the function contains statements like DELETE, UPDATE, INSERT, REPLACE or DDL.

READS SQL DATA

READS SQL DATA means that the function reads data stored in databases, but does not modify any data. This happens if SELECT statements are used, but there no write operations are executed.

CONTAINS SQL

CONTAINS SQL means that the function contains at least one SQL statement, but it does not read or write any data stored in a database. Examples include SET or DO.

NO SQL

NO SQL means nothing, because MariaDB does not currently support any language other than SQL.

Oracle Mode

MariaDB starting with 10.3

From MariaDB 10.3, a subset of Oracle's PL/SQL language has been supported in addition to the traditional SQL/PSM-based MariaDB syntax. See Oracle mode from MariaDB 10.3 for details on changes when running Oracle mode.

Security

You must have the EXECUTE privilege on a function to call it. MariaDB automatically grants the EXECUTE and ALTER ROUTINE privileges to the account that called CREATE FUNCTION, even if the DEFINER clause was used.

Each function has an account associated as the definer. By default, the definer is the account that created the function. Use the DEFINER clause to specify a different account as the definer. You must have the SUPER privilege, or, from MariaDB 10.5.2, the SET USER privilege, to use the DEFINER clause. See Account Names for details on specifying accounts.

The SQL SECURITY clause specifies what privileges are used when a function is called. If SQL SECURITY is INVOKER, the function body will be evaluated using the privileges of the user calling the function. If SQL SECURITY is DEFINER, the function body is always evaluated using the privileges of the definer account. DEFINER is the default.

This allows you to create functions that grant limited access to certain data. For example, say you have a table that stores some employee information, and that you've granted SELECT privileges only on certain columns to the user account roger.

CREATE TABLE employees (name TINYTEXT, dept TINYTEXT, salary INT);
GRANT SELECT (name, dept) ON employees TO roger;

To allow the user the get the maximum salary for a department, define a function and grant the EXECUTE privilege:

CREATE FUNCTION max_salary (dept TINYTEXT) RETURNS INT RETURN
  (SELECT MAX(salary) FROM employees WHERE employees.dept = dept);
GRANT EXECUTE ON FUNCTION max_salary TO roger;

Since SQL SECURITY defaults to DEFINER, whenever the user roger calls this function, the subselect will execute with your privileges. As long as you have privileges to select the salary of each employee, the caller of the function will be able to get the maximum salary for each department without being able to see individual salaries.

Character sets and collations

Function return types can be declared to use any valid character set and collation. If used, the COLLATE attribute needs to be preceded by a CHARACTER SET attribute.

If the character set and collation are not specifically set in the statement, the database defaults at the time of creation will be used. If the database defaults change at a later stage, the stored function character set/collation will not be changed at the same time; the stored function needs to be dropped and recreated to ensure the same character set/collation as the database is used.

Examples

The following example function takes a parameter, performs an operation using an SQL function, and returns the result.

CREATE FUNCTION hello (s CHAR(20))
    RETURNS CHAR(50) DETERMINISTIC
    RETURN CONCAT('Hello, ',s,'!');

SELECT hello('world');
+----------------+
| hello('world') |
+----------------+
| Hello, world!  |
+----------------+

You can use a compound statement in a function to manipulate data with statements like INSERT and UPDATE. The following example creates a counter function that uses a temporary table to store the current value. Because the compound statement contains statements terminated with semicolons, you have to first change the statement delimiter with the DELIMITER statement to allow the semicolon to be used in the function body. See Delimiters in the mysql client for more.

CREATE TEMPORARY TABLE counter (c INT);
INSERT INTO counter VALUES (0);
DELIMITER //
CREATE FUNCTION counter () RETURNS INT
  BEGIN
    UPDATE counter SET c = c + 1;
    RETURN (SELECT c FROM counter LIMIT 1);
  END //
DELIMITER ;

Character set and collation:

CREATE FUNCTION hello2 (s CHAR(20))
  RETURNS CHAR(50) CHARACTER SET 'utf8' COLLATE 'utf8_bin' DETERMINISTIC
  RETURN CONCAT('Hello, ',s,'!');

See Also

1.1.1.3.1.4 CREATE FUNCTION UDF

Syntax

CREATE [OR REPLACE] [AGGREGATE] FUNCTION [IF NOT EXISTS] function_name
    RETURNS {STRING|INTEGER|REAL|DECIMAL}
    SONAME shared_library_name

Contents

  1. Syntax
  2. Description
    1. RETURNS
    2. shared_library_name
    3. AGGREGATE
    4. OR REPLACE
    5. IF NOT EXISTS
    6. Upgrading a UDF
    7. Examples
  3. See Also

Description

A user-defined function (UDF) is a way to extend MariaDB with a new function that works like a native (built-in) MariaDB function such as ABS() or CONCAT().

function_name is the name that should be used in SQL statements to invoke the function.

To create a function, you must have the INSERT privilege for the mysql database. This is necessary becauseCREATE FUNCTION adds a row to the mysql.func system table that records the function's name, type, and shared library name. If you do not have this table, you should run the mysql_upgrade command to create it.

UDFs need to be written in C, C++ or another language that uses C calling conventions, MariaDB needs to have been dynamically compiled, and your operating system must support dynamic loading.

For an example, see sql/udf_example.cc in the source tree. For a collection of existing UDFs see http://www.mysqludf.org/.

Statements making use of user-defined functions are not safe for replication.

For creating a stored function as opposed to a user-defined function, see CREATE FUNCTION.

For valid identifiers to use as function names, see Identifier Names.

RETURNS

The RETURNS clause indicates the type of the function's return value, and can be one of STRING, INTEGER, REAL or DECIMAL. DECIMAL functions currently return string values and should be written like STRING functions.

shared_library_name

shared_library_name is the basename of the shared object file that contains the code that implements the function. The file must be located in the plugin directory. This directory is given by the value of the plugin_dir system variable. Note that before MariaDB/MySQL 5.1, the shared object could be located in any directory that was searched by your system's dynamic linker.

AGGREGATE

Aggregate functions are summary functions such as SUM() and AVG().

MariaDB starting with 10.4

Aggregate UDF functions can be used as window functions.

OR REPLACE

MariaDB starting with 10.1.3

The OR REPLACE clause was added in MariaDB 10.1.3

If the optional OR REPLACE clause is used, it acts as a shortcut for:

DROP FUNCTION IF EXISTS function_name;
CREATE FUNCTION name ...;

IF NOT EXISTS

MariaDB starting with 10.1.3

The IF NOT EXISTS clause was added in MariaDB 10.1.3

When the IF NOT EXISTS clause is used, MariaDB will return a warning instead of an error if the specified function already exists. Cannot be used together with OR REPLACE.

Upgrading a UDF

To upgrade the UDF's shared library, first run a DROP FUNCTION statement, then upgrade the shared library and finally run the CREATE FUNCTION statement. If you upgrade without following this process, you may crash the server.

Examples

CREATE FUNCTION jsoncontains_path RETURNS integer SONAME 'ha_connect.so';
Query OK, 0 rows affected (0.00 sec)

OR REPLACE and IF NOT EXISTS:

CREATE FUNCTION jsoncontains_path RETURNS integer SONAME 'ha_connect.so';
ERROR 1125 (HY000): Function 'jsoncontains_path' already exists

CREATE OR REPLACE FUNCTION jsoncontains_path RETURNS integer SONAME 'ha_connect.so';
Query OK, 0 rows affected (0.00 sec)

CREATE FUNCTION IF NOT EXISTS jsoncontains_path RETURNS integer SONAME 'ha_connect.so';
Query OK, 0 rows affected, 1 warning (0.00 sec)

SHOW WARNINGS;
+-------+------+---------------------------------------------+
| Level | Code | Message                                     |
+-------+------+---------------------------------------------+
| Note  | 1125 | Function 'jsoncontains_path' already exists |
+-------+------+---------------------------------------------+

See Also

1.1.1.3.1.5 CREATE INDEX

Syntax

CREATE [OR REPLACE] [UNIQUE|FULLTEXT|SPATIAL] INDEX 
  [IF NOT EXISTS] index_name
    [index_type]
    ON tbl_name (index_col_name,...)
    [WAIT n | NOWAIT]
    [index_option]
    [algorithm_option | lock_option] ...

index_col_name:
    col_name [(length)] [ASC | DESC]

index_type:
    USING {BTREE | HASH | RTREE}

index_option:
    [ KEY_BLOCK_SIZE [=] value
  | index_type
  | WITH PARSER parser_name
  | COMMENT 'string'
  | CLUSTERING={YES| NO} ]
  [ IGNORED | NOT IGNORED ]

algorithm_option:
    ALGORITHM [=] {DEFAULT|INPLACE|COPY|NOCOPY|INSTANT}

lock_option:
    LOCK [=] {DEFAULT|NONE|SHARED|EXCLUSIVE}

Contents

  1. Syntax
  2. Description
  3. Privileges
  4. Online DDL
  5. CREATE OR REPLACE INDEX
  6. CREATE INDEX IF NOT EXISTS
  7. Index Definitions
  8. WAIT/NOWAIT
  9. ALGORITHM
  10. LOCK
  11. Progress Reporting
  12. WITHOUT OVERLAPS
  13. Examples
  14. See Also

Description

CREATE INDEX is mapped to an ALTER TABLE statement to create indexes. See ALTER TABLE. CREATE INDEX cannot be used to create a PRIMARY KEY; use ALTER TABLE instead.

If another connection is using the table, a metadata lock is active, and this statement will wait until the lock is released. This is also true for non-transactional tables.

Another shortcut, DROP INDEX, allows the removal of an index.

For valid identifiers to use as index names, see Identifier Names.

Note that KEY_BLOCK_SIZE is currently ignored in CREATE INDEX, although it is included in the output of SHOW CREATE TABLE.

Privileges

Executing the CREATE INDEX statement requires the INDEX privilege for the table or the database.

Online DDL

Online DDL is supported with the ALGORITHM and LOCK clauses.

See InnoDB Online DDL Overview for more information on online DDL with InnoDB.

CREATE OR REPLACE INDEX

MariaDB starting with 10.1.4

The OR REPLACE clause was added in MariaDB 10.1.4.

If the OR REPLACE clause is used and if the index already exists, then instead of returning an error, the server will drop the existing index and replace it with the newly defined index.

CREATE INDEX IF NOT EXISTS

If the IF NOT EXISTS clause is used, then the index will only be created if an index with the same name does not already exist. If the index already exists, then a warning will be triggered by default.

Index Definitions

See CREATE TABLE: Index Definitions for information about index definitions.

WAIT/NOWAIT

MariaDB starting with 10.3.0

Set the lock wait timeout. See WAIT and NOWAIT.

ALGORITHM

See ALTER TABLE: ALGORITHM for more information.

LOCK

See ALTER TABLE: LOCK for more information.

Progress Reporting

MariaDB provides progress reporting for CREATE INDEX statement for clients that support the new progress reporting protocol. For example, if you were using the mysql client, then the progress report might look like this::

CREATE INDEX ON tab (num);;
Stage: 1 of 2 'copy to tmp table'    46% of stage

The progress report is also shown in the output of the SHOW PROCESSLIST statement and in the contents of the information_schema.PROCESSLIST table.

See Progress Reporting for more information.

WITHOUT OVERLAPS

MariaDB starting with 10.5.3

The WITHOUT OVERLAPS clause allows one to constrain a primary or unique index such that application-time periods cannot overlap.

Examples

Creating a unique index:

CREATE UNIQUE INDEX HomePhone ON Employees(Home_Phone);

OR REPLACE and IF NOT EXISTS:

CREATE INDEX xi ON xx5 (x);
Query OK, 0 rows affected (0.03 sec)

CREATE INDEX xi ON xx5 (x);
ERROR 1061 (42000): Duplicate key name 'xi'

CREATE OR REPLACE INDEX xi ON xx5 (x);
Query OK, 0 rows affected (0.03 sec)

CREATE INDEX IF NOT EXISTS xi ON xx5 (x);
Query OK, 0 rows affected, 1 warning (0.00 sec)

SHOW WARNINGS;
+-------+------+-------------------------+
| Level | Code | Message                 |
+-------+------+-------------------------+
| Note  | 1061 | Duplicate key name 'xi' |
+-------+------+-------------------------+

From MariaDB 10.5.3, creating a unique index for an application-time period table with a WITHOUT OVERLAPS constraint:

CREATE UNIQUE INDEX u ON rooms (room_number, p WITHOUT OVERLAPS);

See Also

1.1.1.3.1.6 CREATE LOGFILE GROUP

The CREATE LOGFILE GROUP statement is not supported by MariaDB. It was originally inherited from MySQL NDB Cluster. See MDEV-19295 for more information.

1.1.1.3.1.7 CREATE PACKAGE

MariaDB starting with 10.3.5

Oracle-style packages were introduced in MariaDB 10.3.5.

Syntax

CREATE
    [ OR REPLACE]
    [DEFINER = { user | CURRENT_USER | role | CURRENT_ROLE }]
    PACKAGE [ IF NOT EXISTS ]
    [ db_name . ] package_name
    [ package_characteristic ... ]
{ AS | IS }
    [ package_specification_element ... ]
END [ package_name ]


package_characteristic:
    COMMENT 'string'
  | SQL SECURITY { DEFINER | INVOKER }


package_specification_element:
    FUNCTION_SYM package_specification_function ;
  | PROCEDURE_SYM package_specification_procedure ;


package_specification_function:
    func_name [ ( func_param [, func_param]... ) ]
    RETURNS func_return_type
    [ package_routine_characteristic... ]

package_specification_procedure:
    proc_name [ ( proc_param [, proc_param]... ) ]
    [ package_routine_characteristic... ]

func_return_type:
    type

func_param:
    param_name [ IN | OUT | INOUT | IN OUT ] type

proc_param:
    param_name [ IN | OUT | INOUT | IN OUT ] type

type:
    Any valid MariaDB explicit or anchored data type


package_routine_characteristic:
      COMMENT  'string'
    | LANGUAGE SQL
    | { CONTAINS SQL | NO SQL | READS SQL DATA | MODIFIES SQL DATA }
    | SQL SECURITY { DEFINER | INVOKER }

Contents

  1. Syntax
  2. Description
  3. Function parameter quantifiers IN | OUT | INOUT | IN OUT
  4. Examples
  5. See Also

Description

The CREATE PACKAGE statement can be used when Oracle SQL_MODE is set.

The CREATE PACKAGE creates the specification for a stored package (a collection of logically related stored objects). A stored package specification declares public routines (procedures and functions) of the package, but does not implement these routines.

A package whose specification was created by the CREATE PACKAGE statement, should later be implemented using the CREATE PACKAGE BODY statement.

Function parameter quantifiers IN | OUT | INOUT | IN OUT

MariaDB starting with 10.8.0

The function parameter quantifiers for IN, OUT, INOUT, and IN OUT where added in a 10.8.0 preview release. Prior to 10.8.0 quantifiers were supported only in procedures.

OUT, INOUT and its equivalent IN OUT, are only valid if called from SET and not SELECT. These quantifiers are especially useful for creating functions and procedures with more than one return value. This allows functions and procedures to be more complex and nested.

Examples

SET sql_mode=ORACLE;
DELIMITER $$
CREATE OR REPLACE PACKAGE employee_tools AS
  FUNCTION getSalary(eid INT) RETURN DECIMAL(10,2);
  PROCEDURE raiseSalary(eid INT, amount DECIMAL(10,2));
  PROCEDURE raiseSalaryStd(eid INT);
  PROCEDURE hire(ename TEXT, esalary DECIMAL(10,2));
END;
$$
DELIMITER ;

See Also

1.1.1.3.1.8 CREATE PACKAGE BODY

MariaDB starting with 10.3.5

Oracle-style packages were introduced in MariaDB 10.3.5.

Syntax

CREATE [ OR REPLACE ]
    [DEFINER = { user | CURRENT_USER | role | CURRENT_ROLE }]
    PACKAGE BODY
    [ IF NOT EXISTS ]
    [ db_name . ] package_name
    [ package_characteristic... ]
{ AS | IS }
    package_implementation_declare_section
    package_implementation_executable_section
END [ package_name]


package_implementation_declare_section:
    package_implementation_item_declaration
      [ package_implementation_item_declaration... ]
      [ package_implementation_routine_definition... ]
  | package_implementation_routine_definition
      [ package_implementation_routine_definition...]

package_implementation_item_declaration:
    variable_declaration ;

variable_declaration:
    variable_name[,...] type [:= expr ]

package_implementation_routine_definition:
    FUNCTION package_specification_function
       [ package_implementation_function_body ] ;
  | PROCEDURE package_specification_procedure
       [ package_implementation_procedure_body ] ;


package_implementation_function_body:
    { AS | IS } package_routine_body [func_name]

package_implementation_procedure_body:
    { AS | IS } package_routine_body [proc_name]

package_routine_body:
    [ package_routine_declarations ]
    BEGIN
      statements [ EXCEPTION exception_handlers ]
    END


package_routine_declarations:
    package_routine_declaration ';' [package_routine_declaration ';']...


package_routine_declaration:
          variable_declaration
        | condition_name CONDITION FOR condition_value
        | user_exception_name EXCEPTION
        | CURSOR_SYM cursor_name
          [ ( cursor_formal_parameters ) ]
          IS select_statement
        ;


package_implementation_executable_section:
          END
        | BEGIN
            statement ; [statement ; ]...
          [EXCEPTION exception_handlers]
          END

exception_handlers:
           exception_handler [exception_handler...]

exception_handler:
          WHEN_SYM condition_value [, condition_value]...
            THEN_SYM statement ; [statement ;]...

condition_value:
          condition_name
        | user_exception_name
        | SQLWARNING
        | SQLEXCEPTION
        | NOT FOUND
        | OTHERS_SYM
        | SQLSTATE [VALUE] sqlstate_value
        | mariadb_error_code

Contents

  1. Syntax
  2. Description
  3. Examples
  4. See Also

Description

The CREATE PACKAGE BODY statement can be used when Oracle SQL_MODE is set.

The CREATE PACKAGE BODY statement creates the package body for a stored package. The package specification must be previously created using the CREATE PACKAGE statement.

A package body provides implementations of the package public routines and can optionally have:

  • package-wide private variables
  • package private routines
  • forward declarations for private routines
  • an executable initialization section

Examples

SET sql_mode=ORACLE;
DELIMITER $$
CREATE OR REPLACE PACKAGE employee_tools AS
  FUNCTION getSalary(eid INT) RETURN DECIMAL(10,2);
  PROCEDURE raiseSalary(eid INT, amount DECIMAL(10,2));
  PROCEDURE raiseSalaryStd(eid INT);
  PROCEDURE hire(ename TEXT, esalary DECIMAL(10,2));
END;
$$
CREATE PACKAGE BODY employee_tools AS
  -- package body variables
  stdRaiseAmount DECIMAL(10,2):=500;

  -- private routines
  PROCEDURE log (eid INT, ecmnt TEXT) AS
  BEGIN
    INSERT INTO employee_log (id, cmnt) VALUES (eid, ecmnt);
  END;

  -- public routines
  PROCEDURE hire(ename TEXT, esalary DECIMAL(10,2)) AS
    eid INT;
  BEGIN
    INSERT INTO employee (name, salary) VALUES (ename, esalary);
    eid:= last_insert_id();
    log(eid, 'hire ' || ename);
  END;

  FUNCTION getSalary(eid INT) RETURN DECIMAL(10,2) AS
    nSalary DECIMAL(10,2);
  BEGIN
    SELECT salary INTO nSalary FROM employee WHERE id=eid;
    log(eid, 'getSalary id=' || eid || ' salary=' || nSalary);
    RETURN nSalary;
  END;

  PROCEDURE raiseSalary(eid INT, amount DECIMAL(10,2)) AS
  BEGIN
    UPDATE employee SET salary=salary+amount WHERE id=eid;
    log(eid, 'raiseSalary id=' || eid || ' amount=' || amount);
  END;

  PROCEDURE raiseSalaryStd(eid INT) AS
  BEGIN
    raiseSalary(eid, stdRaiseAmount);
    log(eid, 'raiseSalaryStd id=' || eid);
  END;

BEGIN
  -- This code is executed when the current session
  -- accesses any of the package routines for the first time
  log(0, 'Session ' || connection_id() || ' ' || current_user || ' started');
END;
$$

DELIMITER ;

See Also

1.1.1.3.1.9 CREATE PROCEDURE

Syntax

CREATE
    [OR REPLACE]
    [DEFINER = { user | CURRENT_USER | role | CURRENT_ROLE }]
    PROCEDURE sp_name ([proc_parameter[,...]])
    [characteristic ...] routine_body

proc_parameter:
    [ IN | OUT | INOUT ] param_name type

type:
    Any valid MariaDB data type

characteristic:
    LANGUAGE SQL
  | [NOT] DETERMINISTIC
  | { CONTAINS SQL | NO SQL | READS SQL DATA | MODIFIES SQL DATA }
  | SQL SECURITY { DEFINER | INVOKER }
  | COMMENT 'string'

routine_body:
    Valid SQL procedure statement

Contents

  1. Syntax
  2. Description
    1. IN/OUT/INOUT
    2. DETERMINISTIC/NOT DETERMINISTIC
    3. CONTAINS SQL/NO SQL/READS SQL DATA/MODIFIES SQL DATA
    4. Invoking stored procedure from within programs
    5. OR REPLACE
    6. sql_mode
    7. Character Sets and Collations
    8. Oracle Mode
  3. Examples
  4. See Also

Description

Creates a stored procedure. By default, a routine is associated with the default database. To associate the routine explicitly with a given database, specify the name as db_name.sp_name when you create it.

When the routine is invoked, an implicit USE db_name is performed (and undone when the routine terminates). The causes the routine to have the given default database while it executes. USE statements within stored routines are disallowed.

When a stored procedure has been created, you invoke it by using the CALL statement (see CALL).

To execute the CREATE PROCEDURE statement, it is necessary to have the CREATE ROUTINE privilege. By default, MariaDB automatically grants the ALTER ROUTINE and EXECUTE privileges to the routine creator. See also Stored Routine Privileges.

The DEFINER and SQL SECURITY clauses specify the security context to be used when checking access privileges at routine execution time, as described later. Requires the SUPER privilege, or, from MariaDB 10.5.2, the SET USER privilege.

If the routine name is the same as the name of a built-in SQL function, you must use a space between the name and the following parenthesis when defining the routine, or a syntax error occurs. This is also true when you invoke the routine later. For this reason, we suggest that it is better to avoid re-using the names of existing SQL functions for your own stored routines.

The IGNORE_SPACE SQL mode applies to built-in functions, not to stored routines. It is always allowable to have spaces after a routine name, regardless of whether IGNORE_SPACE is enabled.

The parameter list enclosed within parentheses must always be present. If there are no parameters, an empty parameter list of () should be used. Parameter names are not case sensitive.

Each parameter can be declared to use any valid data type, except that the COLLATE attribute cannot be used.

For valid identifiers to use as procedure names, see Identifier Names.

IN/OUT/INOUT

Each parameter is an IN parameter by default. To specify otherwise for a parameter, use the keyword OUT or INOUT before the parameter name.

An IN parameter passes a value into a procedure. The procedure might modify the value, but the modification is not visible to the caller when the procedure returns. An OUT parameter passes a value from the procedure back to the caller. Its initial value is NULL within the procedure, and its value is visible to the caller when the procedure returns. An INOUT parameter is initialized by the caller, can be modified by the procedure, and any change made by the procedure is visible to the caller when the procedure returns.

For each OUT or INOUT parameter, pass a user-defined variable in the CALL statement that invokes the procedure so that you can obtain its value when the procedure returns. If you are calling the procedure from within another stored procedure or function, you can also pass a routine parameter or local routine variable as an IN or INOUT parameter.

DETERMINISTIC/NOT DETERMINISTIC

DETERMINISTIC and NOT DETERMINISTIC apply only to functions. Specifying DETERMINISTC or NON-DETERMINISTIC in procedures has no effect. The default value is NOT DETERMINISTIC. Functions are DETERMINISTIC when they always return the same value for the same input. For example, a truncate or substring function. Any function involving data, therefore, is always NOT DETERMINISTIC.

CONTAINS SQL/NO SQL/READS SQL DATA/MODIFIES SQL DATA

CONTAINS SQL, NO SQL, READS SQL DATA, and MODIFIES SQL DATA are informative clauses that tell the server what the function does. MariaDB does not check in any way whether the specified clause is correct. If none of these clauses are specified, CONTAINS SQL is used by default.

MODIFIES SQL DATA means that the function contains statements that may modify data stored in databases. This happens if the function contains statements like DELETE, UPDATE, INSERT, REPLACE or DDL.

READS SQL DATA means that the function reads data stored in databases, but does not modify any data. This happens if SELECT statements are used, but there no write operations are executed.

CONTAINS SQL means that the function contains at least one SQL statement, but it does not read or write any data stored in a database. Examples include SET or DO.

NO SQL means nothing, because MariaDB does not currently support any language other than SQL.

The routine_body consists of a valid SQL procedure statement. This can be a simple statement such as SELECT or INSERT, or it can be a compound statement written using BEGIN and END. Compound statements can contain declarations, loops, and other control structure statements. See Programmatic and Compound Statements for syntax details.

MariaDB allows routines to contain DDL statements, such as CREATE and DROP. MariaDB also allows stored procedures (but not stored functions) to contain SQL transaction statements such as COMMIT.

For additional information about statements that are not allowed in stored routines, see Stored Routine Limitations.

Invoking stored procedure from within programs

For information about invoking stored procedures from within programs written in a language that has a MariaDB/MySQL interface, see CALL.

OR REPLACE

MariaDB starting with 10.1.3

If the optional OR REPLACE clause is used, it acts as a shortcut for:

DROP PROCEDURE IF EXISTS name;
CREATE PROCEDURE name ...;

with the exception that any existing privileges for the procedure are not dropped.

sql_mode

MariaDB stores the sql_mode system variable setting that is in effect at the time a routine is created, and always executes the routine with this setting in force, regardless of the server SQL mode in effect when the routine is invoked.

Character Sets and Collations

Procedure parameters can be declared with any character set/collation. If the character set and collation are not specifically set, the database defaults at the time of creation will be used. If the database defaults change at a later stage, the stored procedure character set/collation will not be changed at the same time; the stored procedure needs to be dropped and recreated to ensure the same character set/collation as the database is used.

Oracle Mode

MariaDB starting with 10.3

From MariaDB 10.3, a subset of Oracle's PL/SQL language has been supported in addition to the traditional SQL/PSM-based MariaDB syntax. See Oracle mode from MariaDB 10.3 for details on changes when running Oracle mode.

Examples

The following example shows a simple stored procedure that uses an OUT parameter. It uses the DELIMITER command to set a new delimiter for the duration of the process — see Delimiters in the mysql client.

DELIMITER //

CREATE PROCEDURE simpleproc (OUT param1 INT)
 BEGIN
  SELECT COUNT(*) INTO param1 FROM t;
 END;
//

DELIMITER ;

CALL simpleproc(@a);

SELECT @a;
+------+
| @a   |
+------+
|    1 |
+------+

Character set and collation:

DELIMITER //

CREATE PROCEDURE simpleproc2 (
  OUT param1 CHAR(10) CHARACTER SET 'utf8' COLLATE 'utf8_bin'
)
 BEGIN
  SELECT CONCAT('a'),f1 INTO param1 FROM t;
 END;
//

DELIMITER ;

CREATE OR REPLACE:

DELIMITER //

CREATE PROCEDURE simpleproc2 (
  OUT param1 CHAR(10) CHARACTER SET 'utf8' COLLATE 'utf8_bin'
)
 BEGIN
  SELECT CONCAT('a'),f1 INTO param1 FROM t;
 END;
//
ERROR 1304 (42000): PROCEDURE simpleproc2 already exists

DELIMITER ;

DELIMITER //

CREATE OR REPLACE PROCEDURE simpleproc2 (
  OUT param1 CHAR(10) CHARACTER SET 'utf8' COLLATE 'utf8_bin'
)
 BEGIN
  SELECT CONCAT('a'),f1 INTO param1 FROM t;
 END;
//
ERROR 1304 (42000): PROCEDURE simpleproc2 already exists

DELIMITER ;
Query OK, 0 rows affected (0.03 sec)

See Also

1.1.1.3.1.10 CREATE ROLE

1.1.1.3.1.11 CREATE SEQUENCE

1.1.1.3.1.12 CREATE SERVER

Syntax

CREATE [OR REPLACE] SERVER [IF NOT EXISTS] server_name
    FOREIGN DATA WRAPPER wrapper_name
    OPTIONS (option [, option] ...)

option:
  { HOST character-literal
  | DATABASE character-literal
  | USER character-literal
  | PASSWORD character-literal
  | SOCKET character-literal
  | OWNER character-literal
  | PORT numeric-literal }

Contents

  1. Syntax
  2. Description
    1. OR REPLACE
    2. IF NOT EXISTS
  3. Examples
  4. See Also

Description

This statement creates the definition of a server for use with the Spider, Connect, FEDERATED or FederatedX storage engine. The CREATE SERVER statement creates a new row within the servers table within the mysql database. This statement requires the SUPER privilege or, from MariaDB 10.5.2, the FEDERATED ADMIN privilege.

The server_name should be a unique reference to the server. Server definitions are global within the scope of the server, it is not possible to qualify the server definition to a specific database. server_name has a maximum length of 64 characters (names longer than 64 characters are silently truncated), and is case insensitive. You may specify the name as a quoted string.

The wrapper_name may be quoted with single quotes. Supported values are:

For each option you must specify either a character literal or numeric literal. Character literals are UTF-8, support a maximum length of 64 characters and default to a blank (empty) string. String literals are silently truncated to 64 characters. Numeric literals must be a number between 0 and 9999, default value is 0.

Note: The OWNER option is currently not applied, and has no effect on the ownership or operation of the server connection that is created.

The CREATE SERVER statement creates an entry in the mysql.servers table that can later be used with the CREATE TABLE statement when creating a Spider, Connect, FederatedX or FEDERATED table. The options that you specify will be used to populate the columns in the mysql.servers table. The table columns are Server_name, Host, Db, Username, Password, Port and Socket.

DROP SERVER removes a previously created server definition.

CREATE SERVER is not written to the binary log, irrespective of the binary log format being used. From MariaDB 10.1.13, Galera replicates the CREATE SERVER, ALTER SERVER and DROP SERVER statements.

For valid identifiers to use as server names, see Identifier Names.

OR REPLACE

If the optional OR REPLACE clause is used, it acts as a shortcut for:

DROP SERVER IF EXISTS name;
CREATE SERVER server_name ...;

IF NOT EXISTS

If the IF NOT EXISTS clause is used, MariaDB will return a warning instead of an error if the server already exists. Cannot be used together with OR REPLACE.

Examples

CREATE SERVER s
FOREIGN DATA WRAPPER mysql
OPTIONS (USER 'Remote', HOST '192.168.1.106', DATABASE 'test');

OR REPLACE and IF NOT EXISTS:

CREATE SERVER s 
FOREIGN DATA WRAPPER mysql 
OPTIONS (USER 'Remote', HOST '192.168.1.106', DATABASE 'test');
ERROR 1476 (HY000): The foreign server, s, you are trying to create already exists

CREATE OR REPLACE SERVER s 
FOREIGN DATA WRAPPER mysql 
OPTIONS (USER 'Remote', HOST '192.168.1.106', DATABASE 'test');
Query OK, 0 rows affected (0.00 sec)

CREATE SERVER IF NOT EXISTS s 
FOREIGN DATA WRAPPER mysql 
OPTIONS (USER 'Remote', HOST '192.168.1.106', DATABASE 'test');
Query OK, 0 rows affected, 1 warning (0.00 sec)

SHOW WARNINGS;
+-------+------+----------------------------------------------------------------+
| Level | Code | Message                                                        |
+-------+------+----------------------------------------------------------------+
| Note  | 1476 | The foreign server, s, you are trying to create already exists |
+-------+------+----------------------------------------------------------------+

See Also

1.1.1.3.1.13 CREATE TABLE

1.1.1.3.1.14 CREATE TABLESPACE

The CREATE TABLESPACE statement is not supported by MariaDB. It was originally inherited from MySQL NDB Cluster. In MySQL 5.7 and later, the statement is also supported for InnoDB. However, MariaDB has chosen not to include that specific feature. See MDEV-19294 for more information.

1.1.1.3.1.15 CREATE TRIGGER

Syntax

CREATE [OR REPLACE]
    [DEFINER = { user | CURRENT_USER | role | CURRENT_ROLE }]
    TRIGGER [IF NOT EXISTS] trigger_name trigger_time trigger_event
    ON tbl_name FOR EACH ROW
   [{ FOLLOWS | PRECEDES } other_trigger_name ]
   trigger_stmt;

Contents

  1. Syntax
  2. Description
    1. OR REPLACE
    2. DEFINER
    3. IF NOT EXISTS
    4. trigger_time
    5. trigger_event
      1. FOLLOWS/PRECEDES other_trigger_name
    6. Atomic DDL
  3. Examples
  4. See Also

Description

This statement creates a new trigger. A trigger is a named database object that is associated with a table, and that activates when a particular event occurs for the table. The trigger becomes associated with the table named tbl_name, which must refer to a permanent table. You cannot associate a trigger with a TEMPORARY table or a view.

CREATE TRIGGER requires the TRIGGER privilege for the table associated with the trigger.

MariaDB starting with 10.2.3

You can have multiple triggers for the same trigger_time and trigger_event.

For valid identifiers to use as trigger names, see Identifier Names.

OR REPLACE

MariaDB starting with 10.1.4

If used and the trigger already exists, instead of an error being returned, the existing trigger will be dropped and replaced by the newly defined trigger.

DEFINER

The DEFINER clause determines the security context to be used when checking access privileges at trigger activation time. Usage requires the SUPER privilege, or, from MariaDB 10.5.2, the SET USER privilege.

IF NOT EXISTS

MariaDB starting with 10.1.4

If the IF NOT EXISTS clause is used, the trigger will only be created if a trigger of the same name does not exist. If the trigger already exists, by default a warning will be returned.

trigger_time

trigger_time is the trigger action time. It can be BEFORE or AFTER to indicate that the trigger activates before or after each row to be modified.

trigger_event

trigger_event indicates the kind of statement that activates the trigger. The trigger_event can be one of the following:

  • INSERT: The trigger is activated whenever a new row is inserted into the table; for example, through INSERT, LOAD DATA, and REPLACE statements.
  • UPDATE: The trigger is activated whenever a row is modified; for example, through UPDATE statements.
  • DELETE: The trigger is activated whenever a row is deleted from the table; for example, through DELETE and REPLACE statements. However, DROP TABLE and TRUNCATE statements on the table do not activate this trigger, because they do not use DELETE. Dropping a partition does not activate DELETE triggers, either.

FOLLOWS/PRECEDES other_trigger_name

MariaDB starting with 10.2.3

The FOLLOWS other_trigger_name and PRECEDES other_trigger_name options were added in MariaDB 10.2.3 as part of supporting multiple triggers per action time. This is the same syntax used by MySQL 5.7, although MySQL 5.7 does not have multi-trigger support.

FOLLOWS adds the new trigger after another trigger while PRECEDES adds the new trigger before another trigger. If neither option is used, the new trigger is added last for the given action and time.

FOLLOWS and PRECEDES are not stored in the trigger definition. However the trigger order is guaranteed to not change over time. mariadb-dump/mysqldump and other backup methods will not change trigger order. You can verify the trigger order from the ACTION_ORDER column in INFORMATION_SCHEMA.TRIGGERS table.

SELECT trigger_name, action_order FROM information_schema.triggers 
  WHERE event_object_table='t1';

Atomic DDL

MariaDB starting with 10.6.1

MariaDB 10.6.1 supports Atomic DDL and CREATE TRIGGER is atomic.

Examples

CREATE DEFINER=`root`@`localhost` TRIGGER increment_animal
  AFTER INSERT ON animals FOR EACH ROW 
   UPDATE animal_count SET animal_count.animals = animal_count.animals+1;

OR REPLACE and IF NOT EXISTS

CREATE DEFINER=`root`@`localhost` TRIGGER increment_animal
  AFTER INSERT ON animals FOR EACH ROW
    UPDATE animal_count SET animal_count.animals = animal_count.animals+1;
ERROR 1359 (HY000): Trigger already exists

CREATE OR REPLACE DEFINER=`root`@`localhost` TRIGGER increment_animal
  AFTER INSERT ON animals  FOR EACH ROW
    UPDATE animal_count SET animal_count.animals = animal_count.animals+1;
Query OK, 0 rows affected (0.12 sec)

CREATE DEFINER=`root`@`localhost` TRIGGER IF NOT EXISTS increment_animal
  AFTER INSERT ON animals FOR EACH ROW
    UPDATE animal_count SET animal_count.animals = animal_count.animals+1;
Query OK, 0 rows affected, 1 warning (0.00 sec)

SHOW WARNINGS;
+-------+------+------------------------+
| Level | Code | Message                |
+-------+------+------------------------+
| Note  | 1359 | Trigger already exists |
+-------+------+------------------------+
1 row in set (0.00 sec)

See Also

1.1.1.3.1.16 CREATE USER

1.1.1.3.1.17 CREATE VIEW

Syntax

CREATE
    [OR REPLACE]
    [ALGORITHM = {UNDEFINED | MERGE | TEMPTABLE}]
    [DEFINER = { user | CURRENT_USER | role | CURRENT_ROLE }]
    [SQL SECURITY { DEFINER | INVOKER }]
    VIEW [IF NOT EXISTS] view_name [(column_list)]
    AS select_statement
    [WITH [CASCADED | LOCAL] CHECK OPTION]

Contents

  1. Syntax
  2. Description
    1. WITH CHECK OPTION
    2. IF NOT EXISTS
    3. Atomic DDL
  3. Examples
  4. See Also

Description

The CREATE VIEW statement creates a new view, or replaces an existing one if the OR REPLACE clause is given. If the view does not exist, CREATE OR REPLACE VIEW is the same as CREATE VIEW. If the view does exist, CREATE OR REPLACE VIEW is the same as ALTER VIEW.

The select_statement is a SELECT statement that provides the definition of the view. (When you select from the view, you select in effect using the SELECT statement.) select_statement can select from base tables or other views.

The view definition is "frozen" at creation time, so changes to the underlying tables afterwards do not affect the view definition. For example, if a view is defined as SELECT * on a table, new columns added to the table later do not become part of the view. A SHOW CREATE VIEW shows that such queries are rewritten and column names are included in the view definition.

The view definition must be a query that does not return errors at view creation times. However, the base tables used by the views might be altered later and the query may not be valid anymore. In this case, querying the view will result in an error. CHECK TABLE helps in finding this kind of problems.

The ALGORITHM clause affects how MariaDB processes the view. The DEFINER and SQL SECURITY clauses specify the security context to be used when checking access privileges at view invocation time. The WITH CHECK OPTION clause can be given to constrain inserts or updates to rows in tables referenced by the view. These clauses are described later in this section.

The CREATE VIEW statement requires the CREATE VIEW privilege for the view, and some privilege for each column selected by the SELECT statement. For columns used elsewhere in the SELECT statement you must have the SELECT privilege. If the OR REPLACE clause is present, you must also have the DROP privilege for the view.

A view belongs to a database. By default, a new view is created in the default database. To create the view explicitly in a given database, specify the name as db_name.view_name when you create it.

CREATE VIEW test.v AS SELECT * FROM t;

Base tables and views share the same namespace within a database, so a database cannot contain a base table and a view that have the same name.

Views must have unique column names with no duplicates, just like base tables. By default, the names of the columns retrieved by the SELECT statement are used for the view column names. To define explicit names for the view columns, the optional column_list clause can be given as a list of comma-separated identifiers. The number of names in column_list must be the same as the number of columns retrieved by the SELECT statement.

MySQL until 5.1.28

Prior to MySQL 5.1.29, When you modify an existing view, the current view definition is backed up and saved. It is stored in that table's database directory, in a subdirectory named arc. The backup file for a view v is named v.frm-00001. If you alter the view again, the next backup is named v.frm-00002. The three latest view backup definitions are stored. Backed up view definitions are not preserved by mysqldump, or any other such programs, but you can retain them using a file copy operation. However, they are not needed for anything but to provide you with a backup of your previous view definition. It is safe to remove these backup definitions, but only while mysqld is not running. If you delete the arc subdirectory or its files while mysqld is running, you will receive an error the next time you try to alter the view: 

MariaDB [test]> ALTER VIEW v AS SELECT * FROM t; 
ERROR 6 (HY000): Error on delete of '.\test\arc/v.frm-0004' (Errcode: 2)

Columns retrieved by the SELECT statement can be simple references to table columns. They can also be expressions that use functions, constant values, operators, and so forth.

Unqualified table or view names in the SELECT statement are interpreted with respect to the default database. A view can refer to tables or views in other databases by qualifying the table or view name with the proper database name.

A view can be created from many kinds of SELECT statements. It can refer to base tables or other views. It can use joins, UNION, and subqueries. The SELECT need not even refer to any tables. The following example defines a view that selects two columns from another table, as well as an expression calculated from those columns:

CREATE TABLE t (qty INT, price INT);

INSERT INTO t VALUES(3, 50);

CREATE VIEW v AS SELECT qty, price, qty*price AS value FROM t;

SELECT * FROM v;
+------+-------+-------+
| qty  | price | value |
+------+-------+-------+
|    3 |    50 |   150 |
+------+-------+-------+

A view definition is subject to the following restrictions:

  • The SELECT statement cannot contain a subquery in the FROM clause.
  • The SELECT statement cannot refer to system or user variables.
  • Within a stored program, the definition cannot refer to program parameters or local variables.
  • The SELECT statement cannot refer to prepared statement parameters.
  • Any table or view referred to in the definition must exist. However, after a view has been created, it is possible to drop a table or view that the definition refers to. In this case, use of the view results in an error. To check a view definition for problems of this kind, use the CHECK TABLE statement.
  • The definition cannot refer to a TEMPORARY table, and you cannot create a TEMPORARY view.
  • Any tables named in the view definition must exist at definition time.
  • You cannot associate a trigger with a view.
  • For valid identifiers to use as view names, see Identifier Names.

ORDER BY is allowed in a view definition, but it is ignored if you select from a view using a statement that has its own ORDER BY.

For other options or clauses in the definition, they are added to the options or clauses of the statement that references the view, but the effect is undefined. For example, if a view definition includes a LIMIT clause, and you select from the view using a statement that has its own LIMIT clause, it is undefined which limit applies. This same principle applies to options such as ALL, DISTINCT, or SQL_SMALL_RESULT that follow the SELECT keyword, and to clauses such as INTO, FOR UPDATE, and LOCK IN SHARE MODE.

The PROCEDURE clause cannot be used in a view definition, and it cannot be used if a view is referenced in the FROM clause.

If you create a view and then change the query processing environment by changing system variables, that may affect the results that you get from the view:

CREATE VIEW v (mycol) AS SELECT 'abc';

SET sql_mode = '';

SELECT "mycol" FROM v;
+-------+
| mycol |
+-------+
| mycol | 
+-------+

SET sql_mode = 'ANSI_QUOTES';

SELECT "mycol" FROM v;
+-------+
| mycol |
+-------+
| abc   | 
+-------+

The DEFINER and SQL SECURITY clauses determine which MariaDB account to use when checking access privileges for the view when a statement is executed that references the view. They were added in MySQL 5.1.2. The legal SQL SECURITY characteristic values are DEFINER and INVOKER. These indicate that the required privileges must be held by the user who defined or invoked the view, respectively. The default SQL SECURITY value is DEFINER.

If a user value is given for the DEFINER clause, it should be a MariaDB account in 'user_name'@'host_name' format (the same format used in the GRANT statement). The user_name and host_name values both are required. The definer can also be given as CURRENT_USER or CURRENT_USER(). The default DEFINER value is the user who executes the CREATE VIEW statement. This is the same as specifying DEFINER = CURRENT_USER explicitly.

If you specify the DEFINER clause, these rules determine the legal DEFINER user values:

  • If you do not have the SUPER privilege, or, from MariaDB 10.5.2, the SET USER privilege, the only legal user value is your own account, either specified literally or by using CURRENT_USER. You cannot set the definer to some other account.
  • If you have the SUPER privilege, or, from MariaDB 10.5.2, the SET USER privilege, you can specify any syntactically legal account name. If the account does not actually exist, a warning is generated.
  • If the SQL SECURITY value is DEFINER but the definer account does not exist when the view is referenced, an error occurs.

Within a view definition, CURRENT_USER returns the view's DEFINER value by default. For views defined with the SQL SECURITY INVOKER characteristic, CURRENT_USER returns the account for the view's invoker. For information about user auditing within views, see http://dev.mysql.com/doc/refman/5.1/en/account-activity-auditing.html.

Within a stored routine that is defined with the SQL SECURITY DEFINER characteristic, CURRENT_USER returns the routine's DEFINER value. This also affects a view defined within such a program, if the view definition contains a DEFINER value of CURRENT_USER.

View privileges are checked like this:

  • At view definition time, the view creator must have the privileges needed to use the top-level objects accessed by the view. For example, if the view definition refers to table columns, the creator must have privileges for the columns, as described previously. If the definition refers to a stored function, only the privileges needed to invoke the function can be checked. The privileges required when the function runs can be checked only as it executes: For different invocations of the function, different execution paths within the function might be taken.
  • When a view is referenced, privileges for objects accessed by the view are checked against the privileges held by the view creator or invoker, depending on whether the SQL SECURITY characteristic is DEFINER or INVOKER, respectively.
  • If reference to a view causes execution of a stored function, privilege checking for statements executed within the function depend on whether the function is defined with a SQL SECURITY characteristic of DEFINER or INVOKER. If the security characteristic is DEFINER, the function runs with the privileges of its creator. If the characteristic is INVOKER, the function runs with the privileges determined by the view's SQL SECURITY characteristic.

Example: A view might depend on a stored function, and that function might invoke other stored routines. For example, the following view invokes a stored function f():

CREATE VIEW v AS SELECT * FROM t WHERE t.id = f(t.name);

Suppose that f() contains a statement such as this:

IF name IS NULL then
  CALL p1();
ELSE
  CALL p2();
END IF;

The privileges required for executing statements within f() need to be checked when f() executes. This might mean that privileges are needed for p1() or p2(), depending on the execution path within f(). Those privileges must be checked at runtime, and the user who must possess the privileges is determined by the SQL SECURITY values of the view v and the function f().

The DEFINER and SQL SECURITY clauses for views are extensions to standard SQL. In standard SQL, views are handled using the rules for SQL SECURITY INVOKER.

If you invoke a view that was created before MySQL 5.1.2, it is treated as though it was created with a SQL SECURITY DEFINER clause and with a DEFINER value that is the same as your account. However, because the actual definer is unknown, MySQL issues a warning. To make the warning go away, it is sufficient to re-create the view so that the view definition includes a DEFINER clause.

The optional ALGORITHM clause is an extension to standard SQL. It affects how MariaDB processes the view. ALGORITHM takes three values: MERGE, TEMPTABLE, or UNDEFINED. The default algorithm is UNDEFINED if no ALGORITHM clause is present. See View Algorithms for more information.

Some views are updatable. That is, you can use them in statements such as UPDATE, DELETE, or INSERT to update the contents of the underlying table. For a view to be updatable, there must be a one-to-one relationship between the rows in the view and the rows in the underlying table. There are also certain other constructs that make a view non-updatable. See Inserting and Updating with Views.

WITH CHECK OPTION

The WITH CHECK OPTION clause can be given for an updatable view to prevent inserts or updates to rows except those for which the WHERE clause in the select_statement is true.

In a WITH CHECK OPTION clause for an updatable view, the LOCAL and CASCADED keywords determine the scope of check testing when the view is defined in terms of another view. The LOCAL keyword restricts the CHECK OPTION only to the view being defined. CASCADED causes the checks for underlying views to be evaluated as well. When neither keyword is given, the default is CASCADED.

For more information about updatable views and the WITH CHECK OPTION clause, see Inserting and Updating with Views.

IF NOT EXISTS

MariaDB starting with 10.1.3

The IF NOT EXISTS clause was added in MariaDB 10.1.3

When the IF NOT EXISTS clause is used, MariaDB will return a warning instead of an error if the specified view already exists. Cannot be used together with the OR REPLACE clause.

Atomic DDL

MariaDB starting with 10.6.1

MariaDB 10.6.1 supports Atomic DDL and CREATE VIEW is atomic.

Examples

CREATE TABLE t (a INT, b INT) ENGINE = InnoDB;

INSERT INTO t VALUES (1,1), (2,2), (3,3);

CREATE VIEW v AS SELECT a, a*2 AS a2 FROM t;

SELECT * FROM v;
+------+------+
| a    | a2   |
+------+------+
|    1 |    2 |
|    2 |    4 |
|    3 |    6 |
+------+------+

OR REPLACE and IF NOT EXISTS:

CREATE VIEW v AS SELECT a, a*2 AS a2 FROM t;
ERROR 1050 (42S01): Table 'v' already exists

CREATE OR REPLACE VIEW v AS SELECT a, a*2 AS a2 FROM t;
Query OK, 0 rows affected (0.04 sec)

CREATE VIEW IF NOT EXISTS v AS SELECT a, a*2 AS a2 FROM t;
Query OK, 0 rows affected, 1 warning (0.01 sec)

SHOW WARNINGS;
+-------+------+--------------------------+
| Level | Code | Message                  |
+-------+------+--------------------------+
| Note  | 1050 | Table 'v' already exists |
+-------+------+--------------------------+

See Also

1.1.1.3.1.18 Silent Column Changes

When a CREATE TABLE or ALTER TABLE command is issued, MariaDB will silently change a column specification in the following cases:

  • PRIMARY KEY columns are always NOT NULL.
  • Any trailing spaces from SET and ENUM values are discarded.
  • TIMESTAMP columns are always NOT NULL, and display sizes are discarded
  • A row-size limit of 65535 bytes applies
  • If strict SQL mode is not enabled (it is enabled by default from MariaDB 10.2), a VARCHAR column longer than 65535 become TEXT, and a VARBINARY columns longer than 65535 becomes a BLOB. If strict mode is enabled the silent changes will not be made, and an error will occur.
  • If a USING clause specifies an index that's not permitted by the storage engine, the engine will instead use another available index type that can be applied without affecting results.
  • If the CHARACTER SET binary attribute is specified, the column is created as the matching binary data type. A TEXT becomes a BLOB, CHAR a BINARY and VARCHAR a VARBINARY. ENUMs and SETs are created as defined.

To ease imports from other RDBMSs, MariaDB will also silently map the following data types:

Other Vendor TypeMariaDB Type
BOOLTINYINT
BOOLEANTINYINT
CHARACTER VARYING(M)VARCHAR(M)
FIXEDDECIMAL
FLOAT4FLOAT
FLOAT8DOUBLE
INT1TINYINT
INT2SMALLINT
INT3MEDIUMINT
INT4INT
INT8BIGINT
LONG VARBINARYMEDIUMBLOB
LONG VARCHARMEDIUMTEXT
LONGMEDIUMTEXT
MIDDLEINTMEDIUMINT
NUMERICDECIMAL

Currently, all MySQL types are supported in MariaDB.

For type mapping between Cassandra and MariaDB, see Cassandra storage engine.

Example

Silent changes in action:

CREATE TABLE SilenceIsGolden
   (
    f1 TEXT CHARACTER SET binary,
    f2 VARCHAR(15) CHARACTER SET binary,
    f3 CHAR CHARACTER SET binary,
    f4 ENUM('x','y','z') CHARACTER SET binary,
    f5 VARCHAR (65536),
    f6 VARBINARY (65536),
    f7 INT1
   );
Query OK, 0 rows affected, 2 warnings (0.31 sec)

SHOW WARNINGS;
+-------+------+-----------------------------------------------+
| Level | Code | Message                                       |
+-------+------+-----------------------------------------------+
| Note  | 1246 | Converting column 'f5' from VARCHAR to TEXT   |
| Note  | 1246 | Converting column 'f6' from VARBINARY to BLOB |
+-------+------+-----------------------------------------------+

DESCRIBE SilenceIsGolden;
+-------+-------------------+------+-----+---------+-------+
| Field | Type              | Null | Key | Default | Extra |
+-------+-------------------+------+-----+---------+-------+
| f1    | blob              | YES  |     | NULL    |       |
| f2    | varbinary(15)     | YES  |     | NULL    |       |
| f3    | binary(1)         | YES  |     | NULL    |       |
| f4    | enum('x','y','z') | YES  |     | NULL    |       |
| f5    | mediumtext        | YES  |     | NULL    |       |
| f6    | mediumblob        | YES  |     | NULL    |       |
| f7    | tinyint(4)        | YES  |     | NULL    |       |
+-------+-------------------+------+-----+---------+-------+

1.1.1.3.1.19 Generated (Virtual and Persistent/Stored) Columns

Syntax

<type>  [GENERATED ALWAYS]  AS   ( <expression> )
[VIRTUAL | PERSISTENT | STORED]  [UNIQUE] [UNIQUE KEY] [COMMENT <text>]

Contents

  1. Syntax
  2. Description
  3. Supported Features
    1. Storage Engine Support
    2. Data Type Support
    3. Index Support
    4. Statement Support
    5. Expression Support
    6. Making Stored Values Consistent
    7. MySQL Compatibility Support
  4. Implementation Differences
    1. Implementation Differences Compared to Microsoft SQL Server
  5. Development History
  6. Examples
  7. See Also

MariaDB's generated columns syntax is designed to be similar to the syntax for Microsoft SQL Server's computed columns and Oracle Database's virtual columns. In MariaDB 10.2 and later, the syntax is also compatible with the syntax for MySQL's generated columns.

Description

A generated column is a column in a table that cannot explicitly be set to a specific value in a DML query. Instead, its value is automatically generated based on an expression. This expression might generate the value based on the values of other columns in the table, or it might generate the value by calling built-in functions or user-defined functions (UDFs).

There are two types of generated columns:

  • PERSISTENT (a.k.a. STORED): This type's value is actually stored in the table.
  • VIRTUAL: This type's value is not stored at all. Instead, the value is generated dynamically when the table is queried. This type is the default.

Generated columns are also sometimes called computed columns or virtual columns.

Supported Features

Storage Engine Support

  • Generated columns can only be used with storage engines which support them. If you try to use a storage engine that does not support them, then you will see an error similar to the following: 
ERROR 1910 (HY000): TokuDB storage engine does not support computed columns
  • A column in a MERGE table can be built on a PERSISTENT generated column.
    • However, a column in a MERGE table can not be defined as a VIRTUAL and PERSISTENT generated column.

Data Type Support

  • All data types are supported when defining generated columns.
  • Using the ZEROFILL column option is supported when defining generated columns.
MariaDB starting with 10.2.6

In MariaDB 10.2.6 and later, the following statements apply to data types for generated columns:

  • Using the AUTO_INCREMENT column option is not supported when defining generated columns. Previously, it was supported, but this support was removed, because it would not work correctly. See MDEV-11117.

Index Support

  • Using a generated column as a table's primary key is not supported. See MDEV-5590 for more information. If you try to use one as a primary key, then you will see an error similar to the following: 
ERROR 1903 (HY000): Primary key cannot be defined upon a computed column
  • Using PERSISTENT generated columns as part of a foreign key is supported.
  • Referencing PERSISTENT generated columns as part of a foreign key is also supported.
    • However, using the ON UPDATE CASCADE, ON UPDATE SET NULL, or ON DELETE SET NULL clauses is not supported. If you try to use an unsupported clause, then you will see an error similar to the following: 
ERROR 1905 (HY000): Cannot define foreign key with ON UPDATE SET NULL clause on a computed column
MariaDB starting with 10.2.3

In MariaDB 10.2.3 and later, the following statements apply to indexes for generated columns:

  • Defining indexes on both VIRTUAL and PERSISTENT generated columns is supported.
    • If an index is defined on a generated column, then the optimizer considers using it in the same way as indexes based on "real" columns.
MariaDB until 10.2.2

In MariaDB 10.2.2 and before, the following statements apply to indexes for generated columns:

  • Defining indexes on VIRTUAL generated columns is not supported.
  • Defining indexes on PERSISTENT generated columns is supported.
    • If an index is defined on a generated column, then the optimizer considers using it in the same way as indexes based on "real" columns.

Statement Support

  • Generated columns are used in DML queries just as if they were "real" columns.
    • However, VIRTUAL and PERSISTENT generated columns differ in how their data is stored.
      • Values for PERSISTENT generated columns are generated whenever a DML queries inserts or updates the row with the special DEFAULT value. This generates the columns value, and it is stored in the table like the other "real" columns. This value can be read by other DML queries just like the other "real" columns.
      • Values for VIRTUAL generated columns are not stored in the table. Instead, the value is generated dynamically whenever the column is queried. If other columns in a row are queried, but the VIRTUAL generated column is not one of the queried columns, then the column's value is not generated.
  • The SELECT statement supports generated columns.
  • Generated columns can be referenced in the INSERT, UPDATE, and DELETE statements.
    • However, VIRTUAL or PERSISTENT generated columns cannot be explicitly set to any other values than NULL or DEFAULT. If a generated column is explicitly set to any other value, then the outcome depends on whether strict mode is enabled in sql_mode. If it is not enabled, then a warning will be raised and the default generated value will be used instead. If it is enabled, then an error will be raised instead.
  • The CREATE TABLE statement has limited support for generated columns.
    • It supports defining generated columns in a new table.
    • It supports using generated columns to partition tables.
    • It does not support using the versioning clauses with generated columns.
  • The ALTER TABLE statement has limited support for generated columns.
    • It supports the MODIFY and CHANGE clauses for PERSISTENT generated columns.
    • It does not support the MODIFY clause for VIRTUAL generated columns if ALGORITHM is not set to COPY. See MDEV-15476 for more information.
    • It does not support the CHANGE clause for VIRTUAL generated columns if ALGORITHM is not set to COPY. See MDEV-17035 for more information.
    • It does not support altering a table if ALGORITHM is not set to COPY if the table has a VIRTUAL generated column that is indexed. See MDEV-14046 for more information.
    • It does not support adding a VIRTUAL generated column with the ADD clause if the same statement is also adding other columns if ALGORITHM is not set to COPY. See MDEV-17468 for more information.
    • It also does not support altering an existing column into a VIRTUAL generated column.
    • It supports using generated columns to partition tables.
    • It does not support using the versioning clauses with generated columns.
  • The DESCRIBE statement can be used to check whether a table has generated columns.
    • You can tell which columns are generated by looking for the ones where the Extra column is set to either VIRTUAL or PERSISTENT. For example: 
DESCRIBE table1;
+-------+-------------+------+-----+---------+------------+
| Field | Type        | Null | Key | Default | Extra      |
+-------+-------------+------+-----+---------+------------+
| a     | int(11)     | NO   |     | NULL    |            |
| b     | varchar(32) | YES  |     | NULL    |            |
| c     | int(11)     | YES  |     | NULL    | VIRTUAL    |
| d     | varchar(5)  | YES  |     | NULL    | PERSISTENT |
+-------+-------------+------+-----+---------+------------+
  • Generated columns can be properly referenced in the NEW and OLD rows in triggers.
  • The HANDLER statement supports generated columns.

Expression Support

  • Most legal, deterministic expressions which can be calculated are supported in expressions for generated columns.
  • Most built-in functions are supported in expressions for generated columns.
    • However, some built-in functions can't be supported for technical reasons. For example, If you try to use an unsupported function in an expression, an error is generated similar to the following: 
ERROR 1901 (HY000): Function or expression 'dayname()' cannot be used in the GENERATED ALWAYS AS clause of `v`
  • Subqueries are not supported in expressions for generated columns because the underlying data can change.
  • Using anything that depends on data outside the row is not supported in expressions for generated columns.
MariaDB starting with 10.2.1

In MariaDB 10.2.1 and later, the following statements apply to expressions for generated columns:

  • Non-deterministic built-in functions are supported in expressions for not indexed VIRTUAL generated columns.
  • Non-deterministic built-in functions are not supported in expressions for PERSISTENT or indexed VIRTUAL generated columns.
  • User-defined functions (UDFs) are supported in expressions for generated columns.
    • However, MariaDB can't check whether a UDF is deterministic, so it is up to the user to be sure that they do not use non-deterministic UDFs with VIRTUAL generated columns.
  • Defining a generated column based on other generated columns defined before it in the table definition is supported. For example: 
CREATE TABLE t1 (a int as (1), b int as (a));
  • However, defining a generated column based on other generated columns defined after in the table definition is not supported in expressions for generation columns because generated columns are calculated in the order they are defined.
  • Using an expression that exceeds 255 characters in length is supported in expressions for generated columns. The new limit for the entire table definition, including all expressions for generated columns, is 65,535 bytes.
  • Using constant expressions is supported in expressions for generated columns. For example: 
CREATE TABLE t1 (a int as (1));
MariaDB until 10.2.0

In MariaDB 10.2.0 and before, the following statements apply to expressions for generated columns:

  • Non-deterministic built-in functions are not supported in expressions for generated columns.
  • Defining a generated column based on other generated columns defined in the table is not supported. Otherwise, it would generate errors like this: 
ERROR 1900 (HY000): A computed column cannot be based on a computed column
  • Using an expression that exceeds 255 characters in length is not supported in expressions for generated columns.
  • Using constant expressions is not supported in expressions for generated columns. Otherwise, it would generate errors like this: 
ERROR 1908 (HY000): Constant expression in computed column function is not allowed

Making Stored Values Consistent

When a generated column is PERSISTENT or indexed, the value of the expression needs to be consistent regardless of the SQL Mode flags in the current session. If it is not, then the table will be seen as corrupted when the value that should actually be returned by the computed expression and the value that was previously stored and/or indexed using a different sql_mode setting disagree.

There are currently two affected classes of inconsistencies: character padding and unsigned subtraction:

  • For a VARCHAR or TEXT generated column the length of the value returned can vary depending on the PAD_CHAR_TO_FULL_LENGTH sql_mode flag. To make the value consistent, create the generated column using an RTRIM() or RPAD() function. Alternately, create the generated column as a CHAR column so that its data is always fully padded.
  • If a SIGNED generated column is based on the subtraction of an UNSIGNED value, the resulting value can vary depending on how large the value is and the NO_UNSIGNED_SUBTRACTION sql_mode flag. To make the value consistent, use CAST() to ensure that each UNSIGNED operand is SIGNED before the subtraction.
MariaDB starting with 10.5

Beginning in MariaDB 10.5, there is a fatal error generated when trying to create a generated column whose value can change depending on the SQL Mode when its data is PERSISTENT or indexed.

For an existing generated column that has a potentially inconsistent value, a warning about a bad expression is generated the first time it is used (if warnings are enabled).

Beginning in MariaDB 10.4.8, MariaDB 10.3.18, and MariaDB 10.2.27 a potentially inconsistent generated column outputs a warning when created or first used (without restricting their creation).

Here is an example of two tables that would be rejected in MariaDB 10.5 and warned about in the other listed versions:

CREATE TABLE bad_pad (
  txt CHAR(5),
  -- CHAR -> VARCHAR or CHAR -> TEXT can't be persistent or indexed:
  vtxt VARCHAR(5) AS (txt) PERSISTENT
);

CREATE TABLE bad_sub (
  num1 BIGINT UNSIGNED,
  num2 BIGINT UNSIGNED,
  -- The resulting value can vary for some large values
  vnum BIGINT AS (num1 - num2) VIRTUAL,
  KEY(vnum)
);

The warnings for the above tables look like this:

Warning (Code 1901): Function or expression '`txt`' cannot be used in the GENERATED ALWAYS AS clause of `vtxt`
Warning (Code 1105): Expression depends on the @@sql_mode value PAD_CHAR_TO_FULL_LENGTH

Warning (Code 1901): Function or expression '`num1` - `num2`' cannot be used in the GENERATED ALWAYS AS clause of `vnum`
Warning (Code 1105): Expression depends on the @@sql_mode value NO_UNSIGNED_SUBTRACTION

To work around the issue, force the padding or type to make the generated column's expression return a consistent value. For example:

CREATE TABLE good_pad (
  txt CHAR(5),
  -- Using RTRIM() or RPAD() makes the value consistent:
  vtxt VARCHAR(5) AS (RTRIM(txt)) PERSISTENT,
  -- When not persistent or indexed, it is OK for the value to vary by mode:
  vtxt2 VARCHAR(5) AS (txt) VIRTUAL,
  -- CHAR -> CHAR is always OK:
  txt2 CHAR(5) AS (txt) PERSISTENT
);

CREATE TABLE good_sub (
  num1 BIGINT UNSIGNED,
  num2 BIGINT UNSIGNED,
  -- The indexed value will always be consistent in this expression:
  vnum BIGINT AS (CAST(num1 AS SIGNED) - CAST(num2 AS SIGNED)) VIRTUAL,
  KEY(vnum)
);

MySQL Compatibility Support

MariaDB starting with 10.2.1

In MariaDB 10.2.1 and later, the following statements apply to MySQL compatibility for generated columns:

  • The STORED keyword is supported as an alias for the PERSISTENT keyword.
  • Tables created with MySQL 5.7 or later that contain MySQL's generated columns can be imported into MariaDB without a dump and restore.
MariaDB until 10.2.0

In MariaDB 10.2.0 and before, the following statements apply to MySQL compatibility for generated columns:

  • The STORED keyword is not supported as an alias for the PERSISTENT keyword.
  • Tables created with MySQL 5.7 or later that contain MySQL's generated columns can not be imported into MariaDB without a dump and restore.

Implementation Differences

Generated columns are subject to various constraints in other DBMSs that are not present in MariaDB's implementation. Generated columns may also be called computed columns or virtual columns in different implementations. The various details for a specific implementation can be found in the documentation for each specific DBMS.

Implementation Differences Compared to Microsoft SQL Server

MariaDB's generated columns implementation does not enforce the following restrictions that are present in Microsoft SQL Server's computed columns implementation:

  • MariaDB allows server variables in generated column expressions, including those that change dynamically, such as warning_count.
  • MariaDB allows the CONVERT_TZ() function to be called with a named time zone as an argument, even though time zone names and time offsets are configurable.
  • MariaDB allows the CAST() function to be used with non-unicode character sets, even though character sets are configurable and differ between binaries/versions.
  • MariaDB allows FLOAT expressions to be used in generated columns. Microsoft SQL Server considers these expressions to be "imprecise" due to potential cross-platform differences in floating-point implementations and precision.
  • Microsoft SQL Server requires the ARITHABORT mode to be set, so that division by zero returns an error, and not a NULL.
  • Microsoft SQL Server requires QUOTED_IDENTIFIER to be set in sql_mode. In MariaDB, if data is inserted without ANSI_QUOTES set in sql_mode, then it will be processed and stored differently in a generated column that contains quoted identifiers.
  • In MariaDB 10.2.0 and before, it does not allow user-defined functions (UDFs) to be used in expressions for generated columns.

Microsoft SQL Server enforces the above restrictions by doing one of the following things:

  • Refusing to create computed columns.
  • Refusing to allow updates to a table containing them.
  • Refusing to use an index over such a column if it can not be guaranteed that the expression is fully deterministic.

In MariaDB, as long as the sql_mode, language, and other settings that were in effect during the CREATE TABLE remain unchanged, the generated column expression will always be evaluated the same. If any of these things change, then please be aware that the generated column expression might not be evaluated the same way as it previously was.

In MariaDB 5.2, you will get a warning if you try to update a virtual column. In MariaDB 5.3 and later, this warning will be converted to an error if strict mode is enabled in sql_mode.

Development History

Generated columns was originally developed by Andrey Zhakov. It was then modified by Sanja Byelkin and Igor Babaev at Monty Program for inclusion in MariaDB. Monty did the work on MariaDB 10.2 to lift a some of the old limitations.

Examples

Here is an example table that uses both VIRTUAL and PERSISTENT virtual columns:

USE TEST;

CREATE TABLE table1 (
     a INT NOT NULL,
     b VARCHAR(32),
     c INT AS (a mod 10) VIRTUAL,
     d VARCHAR(5) AS (left(b,5)) PERSISTENT);

If you describe the table, you can easily see which columns are virtual by looking in the "Extra" column:

DESCRIBE table1;
+-------+-------------+------+-----+---------+------------+
| Field | Type        | Null | Key | Default | Extra      |
+-------+-------------+------+-----+---------+------------+
| a     | int(11)     | NO   |     | NULL    |            |
| b     | varchar(32) | YES  |     | NULL    |            |
| c     | int(11)     | YES  |     | NULL    | VIRTUAL    |
| d     | varchar(5)  | YES  |     | NULL    | PERSISTENT |
+-------+-------------+------+-----+---------+------------+

To find out what function(s) generate the value of the virtual column you can use SHOW CREATE TABLE:

SHOW CREATE TABLE table1;

| table1 | CREATE TABLE `table1` (
  `a` int(11) NOT NULL,
  `b` varchar(32) DEFAULT NULL,
  `c` int(11) AS (a mod 10) VIRTUAL,
  `d` varchar(5) AS (left(b,5)) PERSISTENT
) ENGINE=MyISAM DEFAULT CHARSET=latin1 |

If you try to insert non-default values into a virtual column, you will receive a warning and what you tried to insert will be ignored and the derived value inserted instead:

WARNINGS;
Show warnings enabled.

INSERT INTO table1 VALUES (1, 'some text',default,default);
Query OK, 1 row affected (0.00 sec)

INSERT INTO table1 VALUES (2, 'more text',5,default);
Query OK, 1 row affected, 1 warning (0.00 sec)

Warning (Code 1645): The value specified for computed column 'c' in table 'table1' has been ignored.

INSERT INTO table1 VALUES (123, 'even more text',default,'something');
Query OK, 1 row affected, 2 warnings (0.00 sec)

Warning (Code 1645): The value specified for computed column 'd' in table 'table1' has been ignored.
Warning (Code 1265): Data truncated for column 'd' at row 1

SELECT * FROM table1;
+-----+----------------+------+-------+
| a   | b              | c    | d     |
+-----+----------------+------+-------+
|   1 | some text      |    1 | some  |
|   2 | more text      |    2 | more  |
| 123 | even more text |    3 | even  |
+-----+----------------+------+-------+
3 rows in set (0.00 sec)

If the ZEROFILL clause is specified, it should be placed directly after the type definition, before the AS (<expression>):

CREATE TABLE table2 (a INT, b INT ZEROFILL AS (a*2) VIRTUAL);
INSERT INTO table2 (a) VALUES (1);

SELECT * FROM table2;
+------+------------+
| a    | b          |
+------+------------+
|    1 | 0000000002 |
+------+------------+
1 row in set (0.00 sec)

You can also use virtual columns to implement a "poor man's partial index". See example at the end of Unique Index.

See Also

1.1.1.3.1.20 Invisible Columns

MariaDB starting with 10.3.3

Invisible columns (sometimes also called hidden columns) first appeared in MariaDB 10.3.3.

Columns can be given an INVISIBLE attribute in a CREATE TABLE or ALTER TABLE statement. These columns will then not be listed in the results of a SELECT * statement, nor do they need to be assigned a value in an INSERT statement, unless INSERT explicitly mentions them by name.

Since SELECT * does not return the invisible columns, new tables or views created in this manner will have no trace of the invisible columns. If specifically referenced in the SELECT statement, the columns will be brought into the view/new table, but the INVISIBLE attribute will not.

Invisible columns can be declared as NOT NULL, but then require a DEFAULT value.

It is not possible for all columns in a table to be invisible.

Examples

CREATE TABLE t (x INT INVISIBLE);
ERROR 1113 (42000): A table must have at least 1 column

CREATE TABLE t (x INT, y INT INVISIBLE, z INT INVISIBLE NOT NULL);
ERROR 4106 (HY000): Invisible column `z` must have a default value

CREATE TABLE t (x INT, y INT INVISIBLE, z INT INVISIBLE NOT NULL DEFAULT 4);

INSERT INTO t VALUES (1),(2);

INSERT INTO t (x,y) VALUES (3,33);

SELECT * FROM t;
+------+
| x    |
+------+
|    1 |
|    2 |
|    3 |
+------+

SELECT x,y,z FROM t;
+------+------+---+
| x    | y    | z |
+------+------+---+
|    1 | NULL | 4 |
|    2 | NULL | 4 |
|    3 |   33 | 4 |
+------+------+---+

DESC t;
+-------+---------+------+-----+---------+-----------+
| Field | Type    | Null | Key | Default | Extra     |
+-------+---------+------+-----+---------+-----------+
| x     | int(11) | YES  |     | NULL    |           |
| y     | int(11) | YES  |     | NULL    | INVISIBLE |
| z     | int(11) | NO   |     | 4       | INVISIBLE |
+-------+---------+------+-----+---------+-----------+

ALTER TABLE t MODIFY x INT INVISIBLE, MODIFY y INT, MODIFY z INT NOT NULL DEFAULT 4;

DESC t;
+-------+---------+------+-----+---------+-----------+
| Field | Type    | Null | Key | Default | Extra     |
+-------+---------+------+-----+---------+-----------+
| x     | int(11) | YES  |     | NULL    | INVISIBLE |
| y     | int(11) | YES  |     | NULL    |           |
| z     | int(11) | NO   |     | 4       |           |
+-------+---------+------+-----+---------+-----------+

Creating a view from a table with hidden columns:

CREATE VIEW v1 AS SELECT * FROM t;

DESC v1;
+-------+---------+------+-----+---------+-------+
| Field | Type    | Null | Key | Default | Extra |
+-------+---------+------+-----+---------+-------+
| y     | int(11) | YES  |     | NULL    |       |
| z     | int(11) | NO   |     | 4       |       |
+-------+---------+------+-----+---------+-------+

CREATE VIEW v2 AS SELECT x,y,z FROM t;

DESC v2;
+-------+---------+------+-----+---------+-------+
| Field | Type    | Null | Key | Default | Extra |
+-------+---------+------+-----+---------+-------+
| x     | int(11) | YES  |     | NULL    |       |
| y     | int(11) | YES  |     | NULL    |       |
| z     | int(11) | NO   |     | 4       |       |
+-------+---------+------+-----+---------+-------+

1.1.1.3.2 ALTER

1.1.1.3.2.1 ALTER TABLE

1.1.1.3.2.2 ALTER DATABASE

1.1.1.3.2.3 ALTER EVENT

1.1.1.3.2.4 ALTER FUNCTION

1.1.1.3.2.5 ALTER LOGFILE GROUP

1.1.1.3.2.6 ALTER PROCEDURE

1.1.1.3.2.7 ALTER SEQUENCE

1.1.1.3.2.8 ALTER SERVER

1.1.1.3.2.9 ALTER TABLESPACE

1.1.1.3.2.10 ALTER USER

1.1.1.3.2.11 ALTER VIEW

1.1.1.3.3 DROP

Articles on various DROP commands.

There are 1 related questions.

1.1.1.3.3.1 DROP DATABASE

Syntax

DROP {DATABASE | SCHEMA} [IF EXISTS] db_name

Contents

  1. Syntax
  2. Description
    1. IF EXISTS
    2. Atomic DDL
  3. Examples
  4. See Also

Description

DROP DATABASE drops all tables in the database and deletes the database. Be very careful with this statement! To use DROP DATABASE, you need the DROP privilege on the database. DROP SCHEMA is a synonym for DROP DATABASE.

Important: When a database is dropped, user privileges on the database are not automatically dropped. See GRANT.

IF EXISTS

Use IF EXISTS to prevent an error from occurring for databases that do not exist. A NOTE is generated for each non-existent database when using IF EXISTS. See SHOW WARNINGS.

Atomic DDL

MariaDB starting with 10.6.1

MariaDB 10.6.1 supports Atomic DDL.

DROP DATABASE is implemented as

loop over all tables
  DROP TABLE table

Each individual DROP TABLE is atomic while DROP DATABASE as a whole is crash-safe.

Examples

DROP DATABASE bufg;
Query OK, 0 rows affected (0.39 sec)

DROP DATABASE bufg;
ERROR 1008 (HY000): Can't drop database 'bufg'; database doesn't exist

 \W
Show warnings enabled.

DROP DATABASE IF EXISTS bufg;
Query OK, 0 rows affected, 1 warning (0.00 sec)
Note (Code 1008): Can't drop database 'bufg'; database doesn't exist

See Also

1.1.1.3.3.2 DROP EVENT

Syntax

DROP EVENT [IF EXISTS] event_name

Description

This statement drops the event named event_name. The event immediately ceases being active, and is deleted completely from the server.

If the event does not exist, the error ERROR 1517 (HY000): Unknown event 'event_name' results. You can override this and cause the statement to generate a NOTE for non-existent events instead by using IF EXISTS. See SHOW WARNINGS.

This statement requires the EVENT privilege. In MySQL 5.1.11 and earlier, an event could be dropped only by its definer, or by a user having the SUPER privilege.

Examples

DROP EVENT myevent3;

Using the IF EXISTS clause:

DROP EVENT IF EXISTS myevent3;
Query OK, 0 rows affected, 1 warning (0.01 sec)

SHOW WARNINGS;
+-------+------+-------------------------------+
| Level | Code | Message                       |
+-------+------+-------------------------------+
| Note  | 1305 | Event myevent3 does not exist |
+-------+------+-------------------------------+

See also

1.1.1.3.3.3 DROP FUNCTION

Syntax

DROP FUNCTION [IF EXISTS] f_name

Contents

  1. Syntax
  2. Description
    1. IF EXISTS
  3. Examples
  4. See Also

Description

The DROP FUNCTION statement is used to drop a stored function or a user-defined function (UDF). That is, the specified routine is removed from the server, along with all privileges specific to the function. You must have the ALTER ROUTINE privilege for the routine in order to drop it. If the automatic_sp_privileges server system variable is set, both the ALTER ROUTINE and EXECUTE privileges are granted automatically to the routine creator - see Stored Routine Privileges.

IF EXISTS

The IF EXISTS clause is a MySQL/MariaDB extension. It prevents an error from occurring if the function does not exist. A NOTE is produced that can be viewed with SHOW WARNINGS.

For dropping a user-defined functions (UDF), see DROP FUNCTION UDF.

Examples

DROP FUNCTION hello;
Query OK, 0 rows affected (0.042 sec)

DROP FUNCTION hello;
ERROR 1305 (42000): FUNCTION test.hello does not exist

DROP FUNCTION IF EXISTS hello;
Query OK, 0 rows affected, 1 warning (0.000 sec)

SHOW WARNINGS;
+-------+------+------------------------------------+
| Level | Code | Message                            |
+-------+------+------------------------------------+
| Note  | 1305 | FUNCTION test.hello does not exist |
+-------+------+------------------------------------+

See Also

1.1.1.3.3.4 DROP FUNCTION UDF

Syntax

DROP FUNCTION [IF EXISTS] function_name

Contents

  1. Syntax
  2. Description
    1. Upgrading a UDF
  3. Examples

Description

This statement drops the user-defined function (UDF) named function_name.

To drop a function, you must have the DELETE privilege for the mysql database. This is because DROP FUNCTION removes the row from the mysql.func system table that records the function's name, type and shared library name.

For dropping a stored function, see DROP FUNCTION.

Upgrading a UDF

To upgrade the UDF's shared library, first run a DROP FUNCTION statement, then upgrade the shared library and finally run the CREATE FUNCTION statement. If you upgrade without following this process, you may crash the server.

Examples

DROP FUNCTION jsoncontains_path;

IF EXISTS:

DROP FUNCTION jsoncontains_path;
ERROR 1305 (42000): FUNCTION test.jsoncontains_path does not exist

DROP FUNCTION IF EXISTS jsoncontains_path;
Query OK, 0 rows affected, 1 warning (0.00 sec)

SHOW WARNINGS;
+-------+------+------------------------------------------------+
| Level | Code | Message                                        |
+-------+------+------------------------------------------------+
| Note  | 1305 | FUNCTION test.jsoncontains_path does not exist |
+-------+------+------------------------------------------------+

1.1.1.3.3.5 DROP INDEX

Syntax

DROP INDEX [IF EXISTS] index_name ON tbl_name 
    [WAIT n |NOWAIT]

Contents

  1. Syntax
  2. Description
  3. Privileges
  4. Online DDL
  5. DROP INDEX IF EXISTS ...
  6. WAIT/NOWAIT
  7. Progress Reporting
  8. See Also

Description

DROP INDEX drops the index named index_name from the table tbl_name. This statement is mapped to an ALTER TABLE statement to drop the index.

If another connection is using the table, a metadata lock is active, and this statement will wait until the lock is released. This is also true for non-transactional tables.

See ALTER TABLE.

Another shortcut, CREATE INDEX, allows the creation of an index.

To remove the primary key, `PRIMARY` must be specified as index_name. Note that the quotes are necessary, because PRIMARY is a keyword.

Privileges

Executing the DROP INDEX statement requires the INDEX privilege for the table or the database.

Online DDL

Online DDL is used by default with InnoDB, when the drop index operation supports it.

See InnoDB Online DDL Overview for more information on online DDL with InnoDB.

DROP INDEX IF EXISTS ...

If the IF EXISTS clause is used, then MariaDB will return a warning instead of an error if the index does not exist.

WAIT/NOWAIT

MariaDB starting with 10.3.0

Set the lock wait timeout. See WAIT and NOWAIT.

Progress Reporting

MariaDB provides progress reporting for DROP INDEX statement for clients that support the new progress reporting protocol. For example, if you were using the mysql client, then the progress report might look like this::

See Also

1.1.1.3.3.6 DROP LOGFILE GROUP

The DROP LOGFILE GROUP statement is not supported by MariaDB. It was originally inherited from MySQL NDB Cluster. See MDEV-19295 for more information.

1.1.1.3.3.7 DROP PACKAGE

MariaDB starting with 10.3.5

Oracle-style packages were introduced in MariaDB 10.3.5.

Syntax

DROP PACKAGE [IF EXISTS]  [ db_name . ] package_name

Contents

  1. Syntax
  2. Description
  3. See Also

Description

The DROP PACKAGE statement can be used when Oracle SQL_MODE is set.

The DROP PACKAGE statement drops a stored package entirely:

  • Drops the package specification (earlier created using the CREATE PACKAGE statement).
  • Drops the package implementation, if the implementation was already created using the CREATE PACKAGE BODY statement.

See Also

1.1.1.3.3.8 DROP PACKAGE BODY

MariaDB starting with 10.3.5

Oracle-style packages were introduced in MariaDB 10.3.5.

Syntax

DROP PACKAGE BODY [IF EXISTS]  [ db_name . ] package_name

Contents

  1. Syntax
  2. Description
  3. See also

Description

The DROP PACKAGE BODY statement can be used when Oracle SQL_MODE is set.

The DROP PACKAGE BODY statement drops the package body (i.e the implementation), previously created using the CREATE PACKAGE BODY statement.

Note, DROP PACKAGE BODY drops only the package implementation, but does not drop the package specification. Use DROP PACKAGE to drop the package entirely (i.e. both implementation and specification).

See also

1.1.1.3.3.9 DROP PROCEDURE

Syntax

DROP PROCEDURE [IF EXISTS] sp_name

Contents

  1. Syntax
  2. Description
  3. Examples
  4. See Also

Description

This statement is used to drop a stored procedure. That is, the specified routine is removed from the server along with all privileges specific to the procedure. You must have the ALTER ROUTINE privilege for the routine. If the automatic_sp_privileges server system variable is set, that privilege and EXECUTE are granted automatically to the routine creator - see Stored Routine Privileges.

The IF EXISTS clause is a MySQL/MariaDB extension. It prevents an error from occurring if the procedure or function does not exist. A NOTE is produced that can be viewed with SHOW WARNINGS.

While this statement takes effect immediately, threads which are executing a procedure can continue execution.

Examples

DROP PROCEDURE simpleproc;

IF EXISTS:

DROP PROCEDURE simpleproc;
ERROR 1305 (42000): PROCEDURE test.simpleproc does not exist

DROP PROCEDURE IF EXISTS simpleproc;
Query OK, 0 rows affected, 1 warning (0.00 sec)

SHOW WARNINGS;
+-------+------+------------------------------------------+
| Level | Code | Message                                  |
+-------+------+------------------------------------------+
| Note  | 1305 | PROCEDURE test.simpleproc does not exist |
+-------+------+------------------------------------------+

See Also

1.1.1.3.3.10 DROP ROLE

1.1.1.3.3.11 DROP SEQUENCE

1.1.1.3.3.12 DROP SERVER

Syntax

DROP SERVER [ IF EXISTS ] server_name

Contents

  1. Syntax
  2. Description
    1. IF EXISTS
  3. Examples
  4. See Also

Description

Drops the server definition for the server named server_name. The corresponding row within the mysql.servers table will be deleted. This statement requires the SUPER privilege or, from MariaDB 10.5.2, the FEDERATED ADMIN privilege.

Dropping a server for a table does not affect any FederatedX, FEDERATED, Connect or Spider tables that used this connection information when they were created.

DROP SERVER is not written to the binary log, irrespective of the binary log format being used. From MariaDB 10.1.13, Galera replicates the CREATE SERVER, ALTER SERVER and DROP SERVER statements.

IF EXISTS

If the IF EXISTS clause is used, MariaDB will not return an error if the server does not exist. Unlike all other statements, DROP SERVER IF EXISTS does not issue a note if the server does not exist. See MDEV-9400.

Examples

DROP SERVER s;

IF EXISTS:

DROP SERVER s;
ERROR 1477 (HY000): The foreign server name you are trying to reference 
  does not exist. Data source error:  s

DROP SERVER IF EXISTS s;
Query OK, 0 rows affected (0.00 sec)

See Also

1.1.1.3.3.13 DROP TABLE

1.1.1.3.3.14 DROP TABLESPACE

The DROP TABLESPACE statement is not supported by MariaDB. It was originally inherited from MySQL NDB Cluster. In MySQL 5.7 and later, the statement is also supported for InnoDB. However, MariaDB has chosen not to include that specific feature. See MDEV-19294 for more information.

1.1.1.3.3.15 DROP TRIGGER

Syntax

DROP TRIGGER [IF EXISTS] [schema_name.]trigger_name

Contents

  1. Syntax
  2. Description
    1. Atomic DDL
  3. Examples
  4. See Also

Description

This statement drops a trigger. The schema (database) name is optional. If the schema is omitted, the trigger is dropped from the default schema. Its use requires the TRIGGER privilege for the table associated with the trigger.

Use IF EXISTS to prevent an error from occurring for a trigger that does not exist. A NOTE is generated for a non-existent trigger when using IF EXISTS. See SHOW WARNINGS.

Note: Triggers for a table are also dropped if you drop the table.

Atomic DDL

MariaDB starting with 10.6.1

MariaDB 10.6.1 supports Atomic DDL and DROP TRIGGER is atomic.

Examples

DROP TRIGGER test.example_trigger;

Using the IF EXISTS clause:

DROP TRIGGER IF EXISTS test.example_trigger;
Query OK, 0 rows affected, 1 warning (0.01 sec)

SHOW WARNINGS;
+-------+------+------------------------+
| Level | Code | Message                |
+-------+------+------------------------+
| Note  | 1360 | Trigger does not exist |
+-------+------+------------------------+

See Also

1.1.1.3.3.16 DROP USER

1.1.1.3.3.17 DROP VIEW

Syntax

DROP VIEW [IF EXISTS]
    view_name [, view_name] ...
    [RESTRICT | CASCADE]

Contents

  1. Syntax
  2. Description
    1. Atomic DDL
  3. Examples
  4. See Also

Description

DROP VIEW removes one or more views. You must have the DROP privilege for each view. If any of the views named in the argument list do not exist, MariaDB returns an error indicating by name which non-existing views it was unable to drop, but it also drops all of the views in the list that do exist.

The IF EXISTS clause prevents an error from occurring for views that don't exist. When this clause is given, a NOTE is generated for each non-existent view. See SHOW WARNINGS.

RESTRICT and CASCADE, if given, are parsed and ignored.

It is possible to specify view names as db_name.view_name. This is useful to delete views from multiple databases with one statement. See Identifier Qualifiers for details.

The DROP privilege is required to use DROP TABLE on non-temporary tables. For temporary tables, no privilege is required, because such tables are only visible for the current session.

If a view references another view, it will be possible to drop the referenced view. However, the other view will reference a view which does not exist any more. Thus, querying it will produce an error similar to the following:

ERROR 1356 (HY000): View 'db_name.view_name' references invalid table(s) or 
column(s) or function(s) or definer/invoker of view lack rights to use them

This problem is reported in the output of CHECK TABLE.

Note that it is not necessary to use DROP VIEW to replace an existing view, because CREATE VIEW has an OR REPLACE clause.

Atomic DDL

MariaDB starting with 10.6.1

MariaDB 10.6.1 supports Atomic DDL and DROP VIEW for a singular view is atomic. Dropping multiple views is crash-safe.

Examples

DROP VIEW v,v2;

Given views v and v2, but no view v3

DROP VIEW v,v2,v3;
ERROR 1051 (42S02): Unknown table 'v3'

DROP VIEW IF EXISTS v,v2,v3;
Query OK, 0 rows affected, 1 warning (0.01 sec)

SHOW WARNINGS;
+-------+------+-------------------------+
| Level | Code | Message                 |
+-------+------+-------------------------+
| Note  | 1051 | Unknown table 'test.v3' |
+-------+------+-------------------------+

See Also

1.1.1.3.4 Atomic DDL

From MariaDB 10.6.1, we have improved readability for DDL (Data Definition Language) operations to make most of them atomic, and the rest crash-safe, even if the server crashes in the middle of an operation.

The design of Atomic/Crash-safe DDL (MDEV-17567) allows it to work with all storage engines.

Definitions

  • Atomic means that either the operation succeeds (and is logged to the binary log or is completely reversed.
  • Crash-safe means that in case of a crash, after the server has restarted, all tables are consistent, there are no temporary files or tables on disk and the binary log matches the status of the server.
  • DDL Data definition language.
  • DML Data manipulation language.
  • 'DDL recovery log' or 'DDL log' for short, is the new log file, ddl-recovery.log by default, that stores all DDL operations in progress. This is used to recover the state of the server in case of sudden crash.

Background

Before 10.6, in case of a crash, there was a small possibility that one of the following things could happen:

  • There could be temporary tables starting with #sql-alter or #sql-shadow or temporary files ending with '' left.
  • The table in the storage engine and the table's .frm file could be out of sync.
  • During a multi-table rename, only some of the tables were renamed.

Which DDL Operations are Now Atomic

  • ALTER SEQUENCE is not listed above as it is internally implemented as a DML.

Which DDL Operations are Now Crash Safe

DROP TABLE of Multiple Tables.

DROP TABLE over multiple tables is treated as if every DROP is a separate, atomic operation. This means that after a crash, all fully, or partly, dropped tables will be dropped and logged to the binary log. The undropped tables will be left untouched.

CREATE OR REPLACE TABLE

CREATE OR REPLACE TABLE foo is implemented as:

DROP TABLE IF EXISTS foo;
CREATE TABLE foo ...

This means that if there is a crash during CREATE TABLE then the original table 'foo' will be dropped even if the new table was not created. If the table was not re-created, the binary log will contain the DROP TABLE.

DROP DATABASE

DROP DATABASE is implemented as:

loop over all tables
  DROP TABLE table

Each DROP TABLE is atomic, but in case of a crash, things will work the same way as DROP TABLE with multiple tables.

Atomic with Different Storage Engines

Atomic/Crash-safe DDL works with all storage engines that either have atomic DDLs internally or are able to re-execute DROP or RENAME in case of failure.

This should be true for most storage engines. The ones that still need some work are:

The DDL Log Recovery File

The new startup option --log-ddl-recovery=path (ddl-recovery.log by default) can be used to specify the place for the DDL log file. This is mainly useful in the case when one has a filesystem on persistent memory, as there is a lot of sync on this file during DDL operations.

This file contains all DDL operations that are in progress.

At MariaDB server startup, the DDL log file is copied to a file with the same base name but with a -backup.log suffix. This is mainly done to be able to find out what went wrong if recovery fails.

If the server crashes during recovery (unlikely but possible), the recovery will continue where it was before. The recovery will retry each entry up to 3 times before giving up and proceeding with the next entry.

Conclusions

  • We believe that a clean separation of layers leads to an easier-to-maintain solution. The Atomic DDL implementation in MariaDB 10.6 introduced minimal changes to the storage engine API, mainly for native ALTER TABLE.
  • In our InnoDB implementation, no file format changes were needed on top of the RENAME undo log that was introduced in MariaDB 10.2.19 for a backup-safe TRUNCATE re-implementation. Correct use of sound design principles (write-ahead logging and transactions; also file creation now follows the ARIES protocol) is sufficient. We removed the hacks (at most one CREATE or DROP per transaction) and correctly implemented rollback and purge triggers for the InnoDB SYS_INDEXES table.
  • Numerous DDL recovery bugs in InnoDB were found and fixed quickly thanks to https://rr-project.org. We are still working on one: data files must not be deleted before the DDL transaction is committed.

Thanks to Atomic/Crash-safe DDL, the MariaDB server is now much more stable and reliable in unstable environments. There is still ongoing work to fix the few remaining issues mentioned above to make all DDL operations Atomic. The target for these is MariaDB 10.7.

See Also

  • MDEV-17567 Atomic DDL. This MDEV entry links to all other entries related to Atomic operations that contains a lot of information how things are implemented.

1.1.1.3.5 CONSTRAINT

MariaDB supports the implementation of constraints at the table-level using either CREATE TABLE or ALTER TABLE statements. A table constraint restricts the data you can add to the table. If you attempt to insert invalid data on a column, MariaDB throws an error.

Syntax

[CONSTRAINT [symbol]] constraint_expression

constraint_expression:
  | PRIMARY KEY [index_type] (index_col_name, ...) [index_option] ...
  | FOREIGN KEY [index_name] (index_col_name, ...) 
       REFERENCES tbl_name (index_col_name, ...)
       [ON DELETE reference_option]
       [ON UPDATE reference_option]
  | UNIQUE [INDEX|KEY] [index_name]
       [index_type] (index_col_name, ...) [index_option] ...
  | CHECK (check_constraints)

index_type:
  USING {BTREE | HASH | RTREE}

index_col_name:
  col_name [(length)] [ASC | DESC]

index_option:
  | KEY_BLOCK_SIZE [=] value
  | index_type
  | WITH PARSER parser_name
  | COMMENT 'string'
  | CLUSTERING={YES|NO}

reference_option:
  RESTRICT | CASCADE | SET NULL | NO ACTION | SET DEFAULT

Contents

  1. Syntax
  2. Description
    1. FOREIGN KEY Constraints
    2. CHECK Constraints
    3. Replication
    4. Auto_increment
  3. Examples
  4. See Also

Description

Constraints provide restrictions on the data you can add to a table. This allows you to enforce data integrity from MariaDB, rather than through application logic. When a statement violates a constraint, MariaDB throws an error.

There are four types of table constraints:

ConstraintDescription
PRIMARY KEYSets the column for referencing rows. Values must be unique and not null.
FOREIGN KEYSets the column to reference the primary key on another table.
UNIQUERequires values in column or columns only occur once in the table.
CHECKChecks whether the data meets the given condition.

The Information Schema TABLE_CONSTRAINTS Table contains information about tables that have constraints.

FOREIGN KEY Constraints

InnoDB supports foreign key constraints. The syntax for a foreign key constraint definition in InnoDB looks like this:

[CONSTRAINT [symbol]] FOREIGN KEY
    [index_name] (index_col_name, ...)
    REFERENCES tbl_name (index_col_name,...)
    [ON DELETE reference_option]
    [ON UPDATE reference_option]

reference_option:
    RESTRICT | CASCADE | SET NULL | NO ACTION

The Information Schema REFERENTIAL_CONSTRAINTS table has more information about foreign keys.

CHECK Constraints

MariaDB starting with 10.2.1

From MariaDB 10.2.1, constraints are enforced. Before MariaDB 10.2.1 constraint expressions were accepted in the syntax but ignored.

In MariaDB 10.2.1 you can define constraints in 2 different ways:

  • CHECK(expression) given as part of a column definition.
  • CONSTRAINT [constraint_name] CHECK (expression)

Before a row is inserted or updated, all constraints are evaluated in the order they are defined. If any constraint expression returns false, then the row will not be inserted or updated. One can use most deterministic functions in a constraint, including UDFs.

CREATE TABLE t1 (a INT CHECK (a>2), b INT CHECK (b>2), CONSTRAINT a_greater CHECK (a>b));

If you use the second format and you don't give a name to the constraint, then the constraint will get an automatically generated name. This is done so that you can later delete the constraint with ALTER TABLE DROP constraint_name.

One can disable all constraint expression checks by setting the check_constraint_checks variable to OFF. This is useful for example when loading a table that violates some constraints that you want to later find and fix in SQL.

Replication

In row-based replication, only the master checks constraints, and failed statements will not be replicated. In statement-based replication, the slaves will also check constraints. Constraints should therefore be identical, as well as deterministic, in a replication environment.

Auto_increment

MariaDB starting with 10.2.6

Examples

CREATE TABLE product (category INT NOT NULL, id INT NOT NULL,
                      price DECIMAL,
                      PRIMARY KEY(category, id)) ENGINE=INNODB;
CREATE TABLE customer (id INT NOT NULL,
                       PRIMARY KEY (id)) ENGINE=INNODB;
CREATE TABLE product_order (no INT NOT NULL AUTO_INCREMENT,
                            product_category INT NOT NULL,
                            product_id INT NOT NULL,
                            customer_id INT NOT NULL,
                            PRIMARY KEY(no),
                            INDEX (product_category, product_id),
                            FOREIGN KEY (product_category, product_id)
                              REFERENCES product(category, id)
                              ON UPDATE CASCADE ON DELETE RESTRICT,
                            INDEX (customer_id),
                            FOREIGN KEY (customer_id)
                              REFERENCES customer(id)) ENGINE=INNODB;
MariaDB starting with 10.2.1

The following examples will work from MariaDB 10.2.1 onwards.

Numeric constraints and comparisons:

CREATE TABLE t1 (a INT CHECK (a>2), b INT CHECK (b>2), CONSTRAINT a_greater CHECK (a>b));

INSERT INTO t1(a) VALUES (1);
ERROR 4022 (23000): CONSTRAINT `a` failed for `test`.`t1`

INSERT INTO t1(a,b) VALUES (3,4);
ERROR 4022 (23000): CONSTRAINT `a_greater` failed for `test`.`t1`

INSERT INTO t1(a,b) VALUES (4,3);
Query OK, 1 row affected (0.04 sec)

Dropping a constraint:

ALTER TABLE t1 DROP CONSTRAINT a_greater;

Adding a constraint:

ALTER TABLE t1 ADD CONSTRAINT a_greater CHECK (a>b);

Date comparisons and character length:

CREATE TABLE t2 (name VARCHAR(30) CHECK (CHAR_LENGTH(name)>2), start_date DATE, 
  end_date DATE CHECK (start_date IS NULL OR end_date IS NULL OR start_date<end_date));

INSERT INTO t2(name, start_date, end_date) VALUES('Ione', '2003-12-15', '2014-11-09');
Query OK, 1 row affected (0.04 sec)

INSERT INTO t2(name, start_date, end_date) VALUES('Io', '2003-12-15', '2014-11-09');
ERROR 4022 (23000): CONSTRAINT `name` failed for `test`.`t2`

INSERT INTO t2(name, start_date, end_date) VALUES('Ione', NULL, '2014-11-09');
Query OK, 1 row affected (0.04 sec)

INSERT INTO t2(name, start_date, end_date) VALUES('Ione', '2015-12-15', '2014-11-09');
ERROR 4022 (23000): CONSTRAINT `end_date` failed for `test`.`t2`

A misplaced parenthesis:

CREATE TABLE t3 (name VARCHAR(30) CHECK (CHAR_LENGTH(name>2)), start_date DATE, 
  end_date DATE CHECK (start_date IS NULL OR end_date IS NULL OR start_date<end_date));
Query OK, 0 rows affected (0.32 sec)

INSERT INTO t3(name, start_date, end_date) VALUES('Io', '2003-12-15', '2014-11-09');
Query OK, 1 row affected, 1 warning (0.04 sec)

SHOW WARNINGS;
+---------+------+----------------------------------------+
| Level   | Code | Message                                |
+---------+------+----------------------------------------+
| Warning | 1292 | Truncated incorrect DOUBLE value: 'Io' |
+---------+------+----------------------------------------+

Compare the definition of table t2 to table t3. CHAR_LENGTH(name)>2 is very different to CHAR_LENGTH(name>2) as the latter mistakenly performs a numeric comparison on the name field, leading to unexpected results.

See Also

1.1.1.3.6 MERGE

1.1.1.3.7 RENAME TABLE

1.1.1.3.8 TRUNCATE TABLE

1.1.1.4 Data Manipulation

SQL commands for querying and manipulating data, such as SELECT, UPDATE, DELETE etc.

There are 3 related questions.

1.1.1.4.1 Selecting Data

The SELECT statement is used for retrieving data from tables, for select specific data, often based on a criteria given in the WHERE clause.

There are 1 related questions.

1.1.1.4.1.1 SELECT

Syntax

SELECT
    [ALL | DISTINCT | DISTINCTROW]
    [HIGH_PRIORITY]
    [STRAIGHT_JOIN]
    [SQL_SMALL_RESULT] [SQL_BIG_RESULT] [SQL_BUFFER_RESULT]
    [SQL_CACHE | SQL_NO_CACHE] [SQL_CALC_FOUND_ROWS]
    select_expr [, select_expr ...]
    [ FROM table_references
      [WHERE where_condition]
      [GROUP BY {col_name | expr | position} [ASC | DESC], ... [WITH ROLLUP]]
      [HAVING where_condition]
      [ORDER BY {col_name | expr | position} [ASC | DESC], ...]
      [LIMIT {[offset,] row_count | row_count OFFSET offset  [ROWS EXAMINED rows_limit] } |
        [OFFSET start { ROW | ROWS }]
        [FETCH { FIRST | NEXT } [ count ] { ROW | ROWS } { ONLY | WITH TIES }] ]
      procedure|[PROCEDURE procedure_name(argument_list)]
      [INTO OUTFILE 'file_name' [CHARACTER SET charset_name] [export_options] |
        INTO DUMPFILE 'file_name' | INTO var_name [, var_name] ]
      [FOR UPDATE lock_option | LOCK IN SHARE MODE lock_option]


export_options:
    [{FIELDS | COLUMNS}
        [TERMINATED BY 'string']
        [[OPTIONALLY] ENCLOSED BY 'char']
        [ESCAPED BY 'char']
    ]
    [LINES
        [STARTING BY 'string']
        [TERMINATED BY 'string']
    ]


lock_option:
    [WAIT n | NOWAIT | SKIP LOCKED]

Contents

  1. Syntax
  2. Description
    1. Select Expressions
    2. DISTINCT
    3. INTO
    4. LIMIT
    5. LOCK IN SHARE MODE/FOR UPDATE
    6. OFFSET ... FETCH
    7. ORDER BY
    8. PARTITION
    9. PROCEDURE
    10. SKIP LOCKED
    11. SQL_CALC_FOUND_ROWS
    12. max_statement_time clause
    13. WAIT/NOWAIT
  3. Examples
  4. See Also

Description

SELECT is used to retrieve rows selected from one or more tables, and can include UNION statements and subqueries.

  • Each select_expr expression indicates a column or data that you want to retrieve. You must have at least one select expression. See Select Expressions below.
  • The FROM clause indicates the table or tables from which to retrieve rows. Use either a single table name or a JOIN expression. See JOIN for details. If no table is involved, FROM DUAL can be specified.
  • Each table can also be specified as db_name.tabl_name. Each column can also be specified as tbl_name.col_name or even db_name.tbl_name.col_name. This allows one to write queries which involve multiple databases. See Identifier Qualifiers for syntax details.
  • The WHERE clause, if given, indicates the condition or conditions that rows must satisfy to be selected. where_condition is an expression that evaluates to true for each row to be selected. The statement selects all rows if there is no WHERE clause.
  • Use the ORDER BY clause to order the results.
  • Use the LIMIT clause allows you to restrict the results to only a certain number of rows, optionally with an offset.
  • Use the GROUP BY and HAVING clauses to group rows together when they have columns or computed values in common.

SELECT can also be used to retrieve rows computed without reference to any table.

Select Expressions

A SELECT statement must contain one or more select expressions, separated by commas. Each select expression can be one of the following:

  • The name of a column.
  • Any expression using functions and operators.
  • * to select all columns from all tables in the FROM clause.
  • tbl_name.* to select all columns from just the table tbl_name.

When specifying a column, you can either use just the column name or qualify the column name with the name of the table using tbl_name.col_name. The qualified form is useful if you are joining multiple tables in the FROM clause. If you do not qualify the column names when selecting from multiple tables, MariaDB will try to find the column in each table. It is an error if that column name exists in multiple tables.

You can quote column names using backticks. If you are qualifying column names with table names, quote each part separately as `tbl_name`.`col_name`.

If you use any grouping functions in any of the select expressions, all rows in your results will be implicitly grouped, as if you had used GROUP BY NULL.

DISTINCT

A query may produce some identical rows. By default, all rows are retrieved, even when their values are the same. To explicitly specify that you want to retrieve identical rows, use the ALL option. If you want duplicates to be removed from the resultset, use the DISTINCT option. DISTINCTROW is a synonym for DISTINCT. See also COUNT DISTINCT and SELECT UNIQUE in Oracle mode.

INTO

The INTO clause is used to specify that the query results should be written to a file or variable.

The reverse of SELECT INTO OUTFILE is LOAD DATA.

LIMIT

Restricts the number of returned rows. See LIMIT and LIMIT ROWS EXAMINED for details.

LOCK IN SHARE MODE/FOR UPDATE

See LOCK IN SHARE MODE and FOR UPDATE for details on the respective locking clauses.

OFFSET ... FETCH

MariaDB starting with 10.6

See SELECT ... OFFSET ... FETCH.

ORDER BY

Order a resultset. See ORDER BY for details.

PARTITION

Specifies to the optimizer which partitions are relevant for the query. Other partitions will not be read. See Partition Pruning and Selection for details.

PROCEDURE

Passes the whole result set to a C Procedure. See PROCEDURE and PROCEDURE ANALYSE (the only built-in procedure not requiring the server to be recompiled).

SKIP LOCKED

MariaDB starting with 10.6

The SKIP LOCKED clause was introduced in MariaDB 10.6.0.

This causes those rows that couldn't be locked (LOCK IN SHARE MODE or FOR UPDATE) to be excluded from the result set. An explicit NOWAIT is implied here. This is only implemented on InnoDB tables and ignored otherwise.

SQL_CALC_FOUND_ROWS

When SQL_CALC_FOUND_ROWS is used, then MariaDB will calculate how many rows would have been in the result, if there would be no LIMIT clause. The result can be found by calling the function FOUND_ROWS() in your next sql statement.


max_statement_time clause

By using max_statement_time in conjunction with SET STATEMENT, it is possible to limit the execution time of individual queries. For example:

SET STATEMENT max_statement_time=100 FOR 
  SELECT field1 FROM table_name ORDER BY field1;

WAIT/NOWAIT

Set the lock wait timeout. See WAIT and NOWAIT.

Examples

SELECT f1,f2 FROM t1 WHERE (f3<=10) AND (f4='y');

See Getting Data from MariaDB (Beginner tutorial), or the various sub-articles, for more examples.

See Also

1.1.1.4.1.2 Joins & Subqueries

Documentation on the JOIN, UNION, EXCEPT and INTERSECT clauses, and on subqueries.

1.1.1.4.1.2.1 Joins

Articles about joins in MariaDB.

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1.1.1.4.1.2.1.1 Joining Tables with JOIN Clauses

1.1.1.4.1.2.1.2 More Advanced Joins

Contents

  1. The Employee Database
  2. Working with the Employee Database
    1. Filtering by Name
    2. Filtering by Name, Date and Time
    3. Displaying Total Work Hours per Day
  3. See Also

This article is a follow up to the Introduction to JOINs page. If you're just getting started with JOINs, go through that page first and then come back here.

The Employee Database

Let us begin by using an example employee database of a fairly small family business, which does not anticipate expanding in the future.

First, we create the table that will hold all of the employees and their contact information:

CREATE TABLE `Employees` (
  `ID` TINYINT(3) UNSIGNED NOT NULL AUTO_INCREMENT,
  `First_Name` VARCHAR(25) NOT NULL,
  `Last_Name` VARCHAR(25) NOT NULL,
  `Position` VARCHAR(25) NOT NULL,
  `Home_Address` VARCHAR(50) NOT NULL,
  `Home_Phone` VARCHAR(12) NOT NULL,
  PRIMARY KEY (`ID`)
) ENGINE=MyISAM;

Next, we add a few employees to the table:

INSERT INTO `Employees` (`First_Name`, `Last_Name`, `Position`, `Home_Address`, `Home_Phone`)
  VALUES
  ('Mustapha', 'Mond', 'Chief Executive Officer', '692 Promiscuous Plaza', '326-555-3492'),
  ('Henry', 'Foster', 'Store Manager', '314 Savage Circle', '326-555-3847'),
  ('Bernard', 'Marx', 'Cashier', '1240 Ambient Avenue', '326-555-8456'),
  ('Lenina', 'Crowne', 'Cashier', '281 Bumblepuppy Boulevard', '328-555-2349'),
  ('Fanny', 'Crowne', 'Restocker', '1023 Bokanovsky Lane', '326-555-6329'),
  ('Helmholtz', 'Watson', 'Janitor', '944 Soma Court', '329-555-2478');

Now, we create a second table, containing the hours which each employee clocked in and out during the week:

CREATE TABLE `Hours` (
  `ID` TINYINT(3) UNSIGNED NOT NULL,
  `Clock_In` DATETIME NOT NULL,
  `Clock_Out` DATETIME NOT NULL
) ENGINE=MyISAM;

Finally, although it is a lot of information, we add a full week of hours for each of the employees into the second table that we created:

INSERT INTO `Hours`
  VALUES
  ('1', '2005-08-08 07:00:42', '2005-08-08 17:01:36'),
  ('1', '2005-08-09 07:01:34', '2005-08-09 17:10:11'),
  ('1', '2005-08-10 06:59:56', '2005-08-10 17:09:29'),
  ('1', '2005-08-11 07:00:17', '2005-08-11 17:00:47'),
  ('1', '2005-08-12 07:02:29', '2005-08-12 16:59:12'),
  ('2', '2005-08-08 07:00:25', '2005-08-08 17:03:13'),
  ('2', '2005-08-09 07:00:57', '2005-08-09 17:05:09'),
  ('2', '2005-08-10 06:58:43', '2005-08-10 16:58:24'),
  ('2', '2005-08-11 07:01:58', '2005-08-11 17:00:45'),
  ('2', '2005-08-12 07:02:12', '2005-08-12 16:58:57'),
  ('3', '2005-08-08 07:00:12', '2005-08-08 17:01:32'),
  ('3', '2005-08-09 07:01:10', '2005-08-09 17:00:26'),
  ('3', '2005-08-10 06:59:53', '2005-08-10 17:02:53'),
  ('3', '2005-08-11 07:01:15', '2005-08-11 17:04:23'),
  ('3', '2005-08-12 07:00:51', '2005-08-12 16:57:52'),
  ('4', '2005-08-08 06:54:37', '2005-08-08 17:01:23'),
  ('4', '2005-08-09 06:58:23', '2005-08-09 17:00:54'),
  ('4', '2005-08-10 06:59:14', '2005-08-10 17:00:12'),
  ('4', '2005-08-11 07:00:49', '2005-08-11 17:00:34'),
  ('4', '2005-08-12 07:01:09', '2005-08-12 16:58:29'),
  ('5', '2005-08-08 07:00:04', '2005-08-08 17:01:43'),
  ('5', '2005-08-09 07:02:12', '2005-08-09 17:02:13'),
  ('5', '2005-08-10 06:59:39', '2005-08-10 17:03:37'),
  ('5', '2005-08-11 07:01:26', '2005-08-11 17:00:03'),
  ('5', '2005-08-12 07:02:15', '2005-08-12 16:59:02'),
  ('6', '2005-08-08 07:00:12', '2005-08-08 17:01:02'),
  ('6', '2005-08-09 07:03:44', '2005-08-09 17:00:00'),
  ('6', '2005-08-10 06:54:19', '2005-08-10 17:03:31'),
  ('6', '2005-08-11 07:00:05', '2005-08-11 17:02:57'),
  ('6', '2005-08-12 07:02:07', '2005-08-12 16:58:23');

Working with the Employee Database

Now that we have a cleanly structured database to work with, let us begin this tutorial by stepping up one notch from the last tutorial and filtering our information a little.

Filtering by Name

Earlier in the week, an anonymous employee reported that Helmholtz came into work almost four minutes late; to verify this, we will begin our investigation by filtering out employees whose first names are "Helmholtz":

SELECT
  `Employees`.`First_Name`,
  `Employees`.`Last_Name`,
  `Hours`.`Clock_In`,
  `Hours`.`Clock_Out`
FROM `Employees`
INNER JOIN `Hours` ON `Employees`.`ID` = `Hours`.`ID`
WHERE `Employees`.`First_Name` = 'Helmholtz';

The result:

+------------+-----------+---------------------+---------------------+
| First_Name | Last_Name | Clock_In            | Clock_Out           |
+------------+-----------+---------------------+---------------------+
| Helmholtz  | Watson    | 2005-08-08 07:00:12 | 2005-08-08 17:01:02 |
| Helmholtz  | Watson    | 2005-08-09 07:03:44 | 2005-08-09 17:00:00 |
| Helmholtz  | Watson    | 2005-08-10 06:54:19 | 2005-08-10 17:03:31 |
| Helmholtz  | Watson    | 2005-08-11 07:00:05 | 2005-08-11 17:02:57 |
| Helmholtz  | Watson    | 2005-08-12 07:02:07 | 2005-08-12 16:58:23 |
+------------+-----------+---------------------+---------------------+
5 rows in set (0.00 sec)

This is obviously more information than we care to trudge through, considering we only care about when he arrived past 7:00:59 on any given day within this week; thus, we need to add a couple more conditions to our WHERE clause.

Filtering by Name, Date and Time

In the following example, we will filter out all of the times which Helmholtz clocked in that were before 7:01:00 and during the work week that lasted from the 8th to the 12th of August:

SELECT
  `Employees`.`First_Name`,
  `Employees`.`Last_Name`,
  `Hours`.`Clock_In`,
  `Hours`.`Clock_Out`
FROM `Employees`
INNER JOIN `Hours` ON `Employees`.`ID` = `Hours`.`ID`
WHERE `Employees`.`First_Name` = 'Helmholtz'
AND DATE_FORMAT(`Hours`.`Clock_In`, '%Y-%m-%d') >= '2005-08-08'
AND DATE_FORMAT(`Hours`.`Clock_In`, '%Y-%m-%d') <= '2005-08-12'
AND DATE_FORMAT(`Hours`.`Clock_In`, '%H:%i:%S') > '07:00:59';

The result:

+------------+-----------+---------------------+---------------------+
| First_Name | Last_Name | Clock_In            | Clock_Out           |
+------------+-----------+---------------------+---------------------+
| Helmholtz  | Watson    | 2005-08-09 07:03:44 | 2005-08-09 17:00:00 |
| Helmholtz  | Watson    | 2005-08-12 07:02:07 | 2005-08-12 16:58:23 |
+------------+-----------+---------------------+---------------------+
2 rows in set (0.00 sec)

We have now, by merely adding a few more conditions, eliminated all of the irrelevant information; Helmholtz was late to work on the 9th and the 12th of August.

Displaying Total Work Hours per Day

Suppose you would like to—based on the information stored in both of our tables in the employee database—develop a quick list of the total hours each employee has worked for each day recorded; a simple way to estimate the time each employee worked per day is exemplified below:

SELECT
  `Employees`.`ID`,
  `Employees`.`First_Name`,
  `Employees`.`Last_Name`,
  `Hours`.`Clock_In`,
  `Hours`.`Clock_Out`,
DATE_FORMAT(`Hours`.`Clock_Out`, '%T')-DATE_FORMAT(`Hours`.`Clock_In`, '%T') AS 'Total_Hours'
FROM `Employees` INNER JOIN `Hours` ON `Employees`.`ID` = `Hours`.`ID`;

The result (limited by 10):

+----+------------+-----------+---------------------+---------------------+-------------+
| ID | First_Name | Last_Name | Clock_In            | Clock_Out           | Total_Hours |
+----+------------+-----------+---------------------+---------------------+-------------+
|  1 | Mustapha   | Mond      | 2005-08-08 07:00:42 | 2005-08-08 17:01:36 |          10 |
|  1 | Mustapha   | Mond      | 2005-08-09 07:01:34 | 2005-08-09 17:10:11 |          10 |
|  1 | Mustapha   | Mond      | 2005-08-10 06:59:56 | 2005-08-10 17:09:29 |          11 |
|  1 | Mustapha   | Mond      | 2005-08-11 07:00:17 | 2005-08-11 17:00:47 |          10 |
|  1 | Mustapha   | Mond      | 2005-08-12 07:02:29 | 2005-08-12 16:59:12 |           9 |
|  2 | Henry      | Foster    | 2005-08-08 07:00:25 | 2005-08-08 17:03:13 |          10 |
|  2 | Henry      | Foster    | 2005-08-09 07:00:57 | 2005-08-09 17:05:09 |          10 |
|  2 | Henry      | Foster    | 2005-08-10 06:58:43 | 2005-08-10 16:58:24 |          10 |
|  2 | Henry      | Foster    | 2005-08-11 07:01:58 | 2005-08-11 17:00:45 |          10 |
|  2 | Henry      | Foster    | 2005-08-12 07:02:12 | 2005-08-12 16:58:57 |           9 |
+----+------------+-----------+---------------------+---------------------+-------------+
10 rows in set (0.00 sec)

See Also

The first version of this article was copied, with permission, from http://hashmysql.org/wiki/More_Advanced_Joins on 2012-10-05.

1.1.1.4.1.2.1.3 JOIN Syntax

Description

MariaDB supports the following JOIN syntaxes for the table_references part of SELECT statements and multiple-table DELETE and UPDATE statements:

table_references:
    table_reference [, table_reference] ...

table_reference:
    table_factor
  | join_table

table_factor:
    tbl_name [PARTITION (partition_list)]
        [query_system_time_period_specification] [[AS] alias] [index_hint_list]
  | table_subquery [query_system_time_period_specification] [AS] alias
  | ( table_references )
  | { ON table_reference LEFT OUTER JOIN table_reference
        ON conditional_expr }

join_table:
    table_reference [INNER | CROSS] JOIN table_factor [join_condition]
  | table_reference STRAIGHT_JOIN table_factor
  | table_reference STRAIGHT_JOIN table_factor ON conditional_expr
  | table_reference {LEFT|RIGHT} [OUTER] JOIN table_reference join_condition
  | table_reference NATURAL [{LEFT|RIGHT} [OUTER]] JOIN table_factor

join_condition:
    ON conditional_expr
  | USING (column_list)

query_system_time_period_specification:
    FOR SYSTEM_TIME AS OF point_in_time
  | FOR SYSTEM_TIME BETWEEN point_in_time AND point_in_time
  | FOR SYSTEM_TIME FROM point_in_time TO point_in_time
  | FOR SYSTEM_TIME ALL

point_in_time:
    [TIMESTAMP] expression
  | TRANSACTION expression

index_hint_list:
    index_hint [, index_hint] ...

index_hint:
    USE {INDEX|KEY}
      [{FOR {JOIN|ORDER BY|GROUP BY}] ([index_list])
  | IGNORE {INDEX|KEY}
      [{FOR {JOIN|ORDER BY|GROUP BY}] (index_list)
  | FORCE {INDEX|KEY}
      [{FOR {JOIN|ORDER BY|GROUP BY}] (index_list)

index_list:
    index_name [, index_name] ...

A table reference is also known as a join expression.

Each table can also be specified as db_name.tabl_name. This allows to write queries which involve multiple databases. See Identifier Qualifiers for syntax details.

The syntax of table_factor is extended in comparison with the SQL Standard. The latter accepts only table_reference, not a list of them inside a pair of parentheses.

This is a conservative extension if we consider each comma in a list of table_reference items as equivalent to an inner join. For example:

SELECT * FROM t1 LEFT JOIN (t2, t3, t4)
                 ON (t2.a=t1.a AND t3.b=t1.b AND t4.c=t1.c)

is equivalent to:

SELECT * FROM t1 LEFT JOIN (t2 CROSS JOIN t3 CROSS JOIN t4)
                 ON (t2.a=t1.a AND t3.b=t1.b AND t4.c=t1.c)

In MariaDB, CROSS JOIN is a syntactic equivalent to INNER JOIN (they can replace each other). In standard SQL, they are not equivalent. INNER JOIN is used with an ON clause, CROSS JOIN is used otherwise.

In general, parentheses can be ignored in join expressions containing only inner join operations. MariaDB also supports nested joins (see http://dev.mysql.com/doc/refman/5.1/en/nested-join-optimization.html).

See System-versioned tables for more information about FOR SYSTEM_TIME syntax.

Index hints can be specified to affect how the MariaDB optimizer makes use of indexes. For more information, see How to force query plans.

Examples

SELECT left_tbl.*
  FROM left_tbl LEFT JOIN right_tbl ON left_tbl.id = right_tbl.id
  WHERE right_tbl.id IS NULL;

1.1.1.4.1.2.1.4 Comma vs JOIN

A query to grab the list of phone numbers for clients who ordered in the last two weeks might be written in a couple of ways. Here are two:

SELECT *
FROM
  clients,
  orders,
  phoneNumbers
WHERE
  clients.id = orders.clientId
  AND clients.id = phoneNumbers.clientId
  AND orderPlaced >= NOW() - INTERVAL 2 WEEK;

SELECT *
FROM
  clients
  INNER JOIN orders ON clients.id = orders.clientId
  INNER JOIN phoneNumbers ON clients.id = phoneNumbers.clientId
WHERE
  orderPlaced >= NOW() - INTERVAL 2 WEEK;

Does it make a difference? Not much as written. But you should use the second form. Why?

  • Readability. Once the WHERE clause contains more than two conditions, it becomes tedious to pick out the difference between business logic (only dates in the last two weeks) and relational logic (which fields relate clients to orders). Using the JOIN syntax with an ON clause makes the WHERE list shorter, and makes it very easy to see how tables relate to each other.
  • Flexibility. Let's say we need to see all clients even if they don't have a phone number in the system. With the second version, it's easy; just change INNER JOIN phoneNumbers to LEFT JOIN phoneNumbers. Try that with the first version, and MySQL version 5.0.12+ will issue a syntax error because of the change in precedence between the comma operator and the JOIN keyword. The solution is to rearrange the FROM clause or add parentheses to override the precedence, and that quickly becomes frustrating.
  • Portability. The changes in 5.0.12 were made to align with SQL:2003. If your queries use standard syntax, you will have an easier time switching to a different database should the need ever arise.

See Also

The initial version of this article was copied, with permission, from http://hashmysql.org/wiki/Comma_vs_JOIN on 2012-10-05.

1.1.1.4.1.2.2 Subqueries

A subquery is a query nested in another query.

There are 1 related questions.

1.1.1.4.1.2.2.1 Scalar Subqueries

A scalar subquery is a subquery that returns a single value. This is the simplest form of a subquery, and can be used in most places a literal or single column value is valid.

The data type, length and character set and collation are all taken from the result returned by the subquery. The result of a subquery can always be NULL, that is, no result returned. Even if the original value is defined as NOT NULL, this is disregarded.

A subquery cannot be used where only a literal is expected, for example LOAD DATA INFILE expects a literal string containing the file name, and LIMIT requires a literal integer.

Examples

CREATE TABLE sq1 (num TINYINT);

CREATE TABLE sq2 (num TINYINT);

INSERT INTO sq1 VALUES (1);

INSERT INTO sq2 VALUES (10* (SELECT num FROM sq1));

SELECT * FROM sq2;
+------+
| num  |
+------+
|   10 |
+------+

Inserting a second row means the subquery is no longer a scalar, and this particular query is not valid:

INSERT INTO sq1 VALUES (2);

INSERT INTO sq2 VALUES (10* (SELECT num FROM sq1));
ERROR 1242 (21000): Subquery returns more than 1 row

No rows in the subquery, so the scalar is NULL:

INSERT INTO sq2 VALUES (10* (SELECT num FROM sq3 WHERE num='3'));

SELECT * FROM sq2;
+------+
| num  |
+------+
|   10 |
| NULL |
+------+

A more traditional scalar subquery, as part of a WHERE clause:

SELECT * FROM sq1 WHERE num = (SELECT MAX(num)/10 FROM sq2); 
+------+
| num  |
+------+
|    1 |
+------+

1.1.1.4.1.2.2.2 Row Subqueries

A row subquery is a subquery returning a single row, as opposed to a scalar subquery, which returns a single column from a row, or a literal.

Examples

CREATE TABLE staff (name VARCHAR(10), age TINYINT);

CREATE TABLE customer (name VARCHAR(10), age TINYINT);

INSERT INTO staff VALUES ('Bilhah',37), ('Valerius',61), ('Maia',25);

INSERT INTO customer VALUES ('Thanasis',48), ('Valerius',61), ('Brion',51);

SELECT * FROM staff WHERE (name,age) = (SELECT name,age FROM customer WHERE name='Valerius');
+----------+------+
| name     | age  |
+----------+------+
| Valerius |   61 |
+----------+------+

Finding all rows in one table also in another:

SELECT name,age FROM staff WHERE (name,age) IN (SELECT name,age FROM customer);
+----------+------+
| name     | age  |
+----------+------+
| Valerius |   61 |
+----------+------+

1.1.1.4.1.2.2.3 Subqueries and ALL

Contents

  1. Syntax
  2. Examples

Subqueries using the ALL keyword will return true if the comparison returns true for each row returned by the subquery, or the subquery returns no rows.

Syntax

scalar_expression comparison_operator ALL <Table subquery>
  • scalar_expression may be any expression that evaluates to a single value
  • comparison_operator may be any one of: =, >, <, >=, <=, <> or !=

ALL returns:

  • NULL if the comparison operator returns NULL for at least one row returned by the Table subquery or scalar_expression returns NULL.
  • FALSE if the comparison operator returns FALSE for at least one row returned by the Table subquery.
  • TRUE if the comparison operator returns TRUE for all rows returned by the Table subquery, or if Table subquery returns no rows.

NOT IN is an alias for <> ALL.

Examples

CREATE TABLE sq1 (num TINYINT);

CREATE TABLE sq2 (num2 TINYINT);

INSERT INTO sq1 VALUES(100);

INSERT INTO sq2 VALUES(40),(50),(60);

SELECT * FROM sq1 WHERE num > ALL (SELECT * FROM sq2);
+------+
| num  |
+------+
|  100 |
+------+

Since 100 > all of 40,50 and 60, the evaluation is true and the row is returned

Adding a second row to sq1, where the evaluation for that record is false:

INSERT INTO sq1 VALUES(30);

SELECT * FROM sq1 WHERE num > ALL (SELECT * FROM sq2);
+------+
| num  |
+------+
|  100 |
+------+

Adding a new row to sq2, causing all evaluations to be false:

INSERT INTO sq2 VALUES(120);

SELECT * FROM sq1 WHERE num > ALL (SELECT * FROM sq2);
Empty set (0.00 sec)

When the subquery returns no results, the evaluation is still true:

SELECT * FROM sq1 WHERE num > ALL (SELECT * FROM sq2 WHERE num2 > 300);
+------+
| num  |
+------+
|  100 |
|   30 |
+------+

Evaluating against a NULL will cause the result to be unknown, or not true, and therefore return no rows:

INSERT INTO sq2 VALUES (NULL);

SELECT * FROM sq1 WHERE num > ALL (SELECT * FROM sq2);

1.1.1.4.1.2.2.4 Subqueries and ANY

Contents

  1. Syntax
  2. Examples

Subqueries using the ANY keyword will return true if the comparison returns true for at least one row returned by the subquery.

Syntax

The required syntax for an ANY or SOME quantified comparison is:

scalar_expression comparison_operator ANY <Table subquery>

Or:

scalar_expression comparison_operator SOME <Table subquery>
  • scalar_expression may be any expression that evaluates to a single value.
  • comparison_operator may be any one of =, >, <, >=, <=, <> or !=.

ANY returns:

  • TRUE if the comparison operator returns TRUE for at least one row returned by the Table subquery.
  • FALSE if the comparison operator returns FALSE for all rows returned by the Table subquery, or Table subquery has zero rows.
  • NULL if the comparison operator returns NULL for at least one row returned by the Table subquery and doesn't returns TRUE for any of them, or if scalar_expression returns NULL.

SOME is a synmonym for ANY, and IN is a synonym for = ANY

Examples

CREATE TABLE sq1 (num TINYINT);

CREATE TABLE sq2 (num2 TINYINT);

INSERT INTO sq1 VALUES(100);

INSERT INTO sq2 VALUES(40),(50),(120);

SELECT * FROM sq1 WHERE num > ANY (SELECT * FROM sq2);
+------+
| num  |
+------+
|  100 |
+------+

100 is greater than two of the three values, and so the expression evaluates as true.

SOME is a synonym for ANY:

SELECT * FROM sq1 WHERE num < SOME (SELECT * FROM sq2);
+------+
| num  |
+------+
|  100 |
+------+

IN is a synonym for = ANY, and here there are no matches, so no results are returned:

SELECT * FROM sq1 WHERE num IN (SELECT * FROM sq2);
Empty set (0.00 sec)

INSERT INTO sq2 VALUES(100);
Query OK, 1 row affected (0.05 sec)

SELECT * FROM sq1 WHERE num <> ANY (SELECT * FROM sq2);
+------+
| num  |
+------+
|  100 |
+------+

Reading this query, the results may be counter-intuitive. It may seem to read as "SELECT * FROM sq1 WHERE num does not match any results in sq2. Since it does match 100, it could seem that the results are incorrect. However, the query returns a result if the match does not match any of sq2. Since 100 already does not match 40, the expression evaluates to true immediately, regardless of the 100's matching. It may be more easily readable to use SOME in a case such as this:

SELECT * FROM sq1 WHERE num <> SOME (SELECT * FROM sq2);
+------+
| num  |
+------+
|  100 |
+------+

1.1.1.4.1.2.2.5 Subqueries and EXISTS

Syntax

SELECT ... WHERE EXISTS <Table subquery>

Description

Subqueries using the EXISTS keyword will return true if the subquery returns any rows. Conversely, subqueries using NOT EXISTS will return true only if the subquery returns no rows from the table.

EXISTS subqueries ignore the columns specified by the SELECT of the subquery, since they're not relevant. For example, 

SELECT col1 FROM t1 WHERE EXISTS (SELECT * FROM t2);

and 

SELECT col1 FROM t1 WHERE EXISTS (SELECT col2 FROM t2);

produce identical results.

Examples

CREATE TABLE sq1 (num TINYINT);

CREATE TABLE sq2 (num2 TINYINT);

INSERT INTO sq1 VALUES(100);

INSERT INTO sq2 VALUES(40),(50),(60);

SELECT * FROM sq1 WHERE EXISTS (SELECT * FROM sq2 WHERE num2>50);
+------+
| num  |
+------+
|  100 |
+------+

SELECT * FROM sq1 WHERE NOT EXISTS (SELECT * FROM sq2 GROUP BY num2 HAVING MIN(num2)=40);
Empty set (0.00 sec)

1.1.1.4.1.2.2.6 Subqueries in a FROM Clause

Although subqueries are more commonly placed in a WHERE clause, they can also form part of the FROM clause. Such subqueries are commonly called derived tables.

If a subquery is used in this way, you must also use an AS clause to name the result of the subquery.

ORACLE mode

MariaDB starting with 10.6.0

From MariaDB 10.6.0, anonymous subqueries in a FROM clause (no AS clause) are permitted in ORACLE mode.

Examples

CREATE TABLE student (name CHAR(10), test CHAR(10), score TINYINT); 

INSERT INTO student VALUES 
  ('Chun', 'SQL', 75), ('Chun', 'Tuning', 73), 
  ('Esben', 'SQL', 43), ('Esben', 'Tuning', 31), 
  ('Kaolin', 'SQL', 56), ('Kaolin', 'Tuning', 88), 
  ('Tatiana', 'SQL', 87), ('Tatiana', 'Tuning', 83);

Assume that, given the data above, you want to return the average total for all students. In other words, the average of Chun's 148 (75+73), Esben's 74 (43+31), etc.

You cannot do the following:

SELECT AVG(SUM(score)) FROM student GROUP BY name;
ERROR 1111 (HY000): Invalid use of group function

A subquery in the FROM clause is however permitted:

SELECT AVG(sq_sum) FROM (SELECT SUM(score) AS sq_sum FROM student GROUP BY name) AS t;
+-------------+
| AVG(sq_sum) |
+-------------+
|    134.0000 |
+-------------+

From MariaDB 10.6 in ORACLE mode, the following is permitted:

SELECT * FROM (SELECT 1 FROM DUAL), (SELECT 2 FROM DUAL);

1.1.1.4.1.2.2.7 Subquery Optimizations

1.1.1.4.1.2.2.7.1 Subquery Optimizations Map

1.1.1.4.1.2.2.7.2 Semi-join Subquery Optimizations

1.1.1.4.1.2.2.7.3 Table Pullout Optimization

1.1.1.4.1.2.2.7.4 Non-semi-join Subquery Optimizations

1.1.1.4.1.2.2.7.5 Subquery Cache

1.1.1.4.1.2.2.7.6 Condition Pushdown Into IN subqueries

1.1.1.4.1.2.2.7.7 Conversion of Big IN Predicates Into Subqueries

1.1.1.4.1.2.2.7.8 EXISTS-to-IN Optimization

1.1.1.4.1.2.2.7.9 Optimizing GROUP BY and DISTINCE Clauses in Subqueries

1.1.1.4.1.2.2.8 Subqueries and JOINs

A subquery can quite often, but not in all cases, be rewritten as a JOIN.

Contents

  1. Rewriting Subqueries as JOINS
  2. Using Subqueries instead of JOINS

Rewriting Subqueries as JOINS

A subquery using IN can be rewritten with the DISTINCT keyword, for example:

SELECT * FROM table1 WHERE col1 IN (SELECT col1 FROM table2);

can be rewritten as:

SELECT DISTINCT table1.* FROM table1, table2 WHERE table1.col1=table2.col1;

NOT IN or NOT EXISTS queries can also be rewritten. For example, these two queries returns the same result:

SELECT * FROM table1 WHERE col1 NOT IN (SELECT col1 FROM table2);
SELECT * FROM table1 WHERE NOT EXISTS (SELECT col1 FROM table2 WHERE table1.col1=table2.col1);

and both can be rewritten as:

SELECT table1.* FROM table1 LEFT JOIN table2 ON table1.id=table2.id WHERE table2.id IS NULL;

Subqueries that can be rewritten as a LEFT JOIN are sometimes more efficient.

Using Subqueries instead of JOINS

There are some scenarios, though, which call for subqueries rather than joins:

  • When you want duplicates, but not false duplicates. Suppose Table_1 has three rows — {1,1,2} — and Table_2 has two rows — {1,2,2}. If you need to list the rows in Table_1 which are also in Table_2, only this subquery-based SELECT statement will give the right answer (1,1,2): 
SELECT Table_1.column_1 
FROM   Table_1 
WHERE  Table_1.column_1 IN 
  (SELECT Table_2.column_1 
    FROM   Table_2);
  • This SQL statement won't work: 
SELECT Table_1.column_1 
FROM   Table_1,Table_2 
WHERE  Table_1.column_1 = Table_2.column_1;
  • because the result will be {1,1,2,2} — and the duplication of 2 is an error. This SQL statement won't work either: 
SELECT DISTINCT Table_1.column_1 
FROM   Table_1,Table_2 
WHERE  Table_1.column_1 = Table_2.column_1;
  • because the result will be {1,2} — and the removal of the duplicated 1 is an error too.
  • When the outermost statement is not a query. The SQL statement: 
UPDATE Table_1 SET column_1 = (SELECT column_1 FROM Table_2);
  • can't be expressed using a join unless some rare SQL3 features are used.
  • When the join is over an expression. The SQL statement: 
SELECT * FROM Table_1 
WHERE column_1 + 5 =
  (SELECT MAX(column_1) FROM Table_2);
  • is hard to express with a join. In fact, the only way we can think of is this SQL statement: 
SELECT Table_1.*
FROM   Table_1, 
      (SELECT MAX(column_1) AS max_column_1 FROM Table_2) AS Table_2
WHERE  Table_1.column_1 + 5 = Table_2.max_column_1;
  • which still involves a parenthesized query, so nothing is gained from the transformation.
  • When you want to see the exception. For example, suppose the question is: what books are longer than Das Kapital? These two queries are effectively almost the same: 
SELECT DISTINCT Bookcolumn_1.*                     
FROM   Books AS Bookcolumn_1 JOIN Books AS Bookcolumn_2 USING(page_count) 
WHERE  title = 'Das Kapital';

SELECT DISTINCT Bookcolumn_1.* 
FROM   Books AS Bookcolumn_1 
WHERE  Bookcolumn_1.page_count > 
  (SELECT DISTINCT page_count 
  FROM   Books AS Bookcolumn_2 
  WHERE  title = 'Das Kapital');
  • The difference is between these two SQL statements is, if there are two editions of Das Kapital (with different page counts), then the self-join example will return the books which are longer than the shortest edition of Das Kapital. That might be the wrong answer, since the original question didn't ask for "... longer than ANY book named Das Kapital" (it seems to contain a false assumption that there's only one edition).

1.1.1.4.1.2.2.9 Subquery Limitations

Contents

  1. ORDER BY and LIMIT
  2. Modifying and Selecting from the Same Table
  3. Row Comparison Operations
  4. Correlated Subqueries
  5. Stored Functions



There are a number of limitations regarding subqueries, which are discussed below.

The following tables and data will be used in the examples that follow: 


CREATE TABLE staff(name VARCHAR(10),age TINYINT);

CREATE TABLE customer(name VARCHAR(10),age TINYINT);

INSERT INTO staff VALUES 
('Bilhah',37), ('Valerius',61), ('Maia',25);

INSERT INTO customer VALUES 
('Thanasis',48), ('Valerius',61), ('Brion',51);

ORDER BY and LIMIT

To use ORDER BY or limit LIMIT in subqueries both must be used.. For example:

SELECT * FROM staff WHERE name IN (SELECT name FROM customer ORDER BY name);
+----------+------+
| name     | age  |
+----------+------+
| Valerius |   61 |
+----------+------+

is valid, but 

SELECT * FROM staff WHERE name IN (SELECT NAME FROM customer ORDER BY name LIMIT 1);
ERROR 1235 (42000): This version of MariaDB doesn't 
  yet support 'LIMIT & IN/ALL/ANY/SOME subquery'

is not.

Modifying and Selecting from the Same Table

It's not possible to both modify and select from the same table in a subquery. For example:

DELETE FROM staff WHERE name = (SELECT name FROM staff WHERE age=61);
ERROR 1093 (HY000): Table 'staff' is specified twice, both 
  as a target for 'DELETE' and as a separate source for data

Row Comparison Operations

There is only partial support for row comparison operations. The expression in

expr op {ALL|ANY|SOME} subquery,

must be scalar and the subquery can only return a single column.

However, because of the way IN is implemented (it is rewritten as a sequence of = comparisons and AND), the expression in 

expression [NOT] IN subquery

is permitted to be an n-tuple and the subquery can return rows of n-tuples.

For example:

SELECT * FROM staff WHERE (name,age) NOT IN (
  SELECT name,age FROM customer WHERE age >=51]
);
+--------+------+
| name   | age  |
+--------+------+
| Bilhah |   37 |
| Maia   |   25 |
+--------+------+

is permitted, but 

SELECT * FROM staff WHERE (name,age) = ALL (
  SELECT name,age FROM customer WHERE age >=51
);
ERROR 1241 (21000): Operand should contain 1 column(s)

is not.

Correlated Subqueries

Subqueries in the FROM clause cannot be correlated subqueries. They cannot be evaluated for each row of the outer query since they are evaluated to produce a result set during when the query is executed.

Stored Functions

A subquery can refer to a stored function which modifies data. This is an extension to the SQL standard, but can result in indeterminate outcomes. For example, take:

SELECT ... WHERE x IN (SELECT f() ...);

where f() inserts rows. The function f() could be executed a different number of times depending on how the optimizer chooses to handle the query.

This sort of construct is therefore not safe to use in replication that is not row-based, as there could be different results on the master and the slave.

1.1.1.4.1.2.3 UNION

UNION is used to combine the results from multiple SELECT statements into a single result set.

Syntax

SELECT ...
UNION [ALL | DISTINCT] SELECT ...
[UNION [ALL | DISTINCT] SELECT ...]
[ORDER BY [column [, column ...]]]
[LIMIT {[offset,] row_count | row_count OFFSET offset}]

Contents

  1. Syntax
  2. Description
    1. ALL/DISTINCT
    2. ORDER BY and LIMIT
    3. HIGH_PRIORITY
    4. SELECT ... INTO ...
    5. Parentheses
  3. Examples
  4. See Also

Description

UNION is used to combine the results from multiple SELECT statements into a single result set.

The column names from the first SELECT statement are used as the column names for the results returned. Selected columns listed in corresponding positions of each SELECT statement should have the same data type. (For example, the first column selected by the first statement should have the same type as the first column selected by the other statements.)

If they don't, the type and length of the columns in the result take into account the values returned by all of the SELECTs, so there is no need for explicit casting. Note that currently this is not the case for recursive CTEs - see MDEV-12325.

Table names can be specified as db_name.tbl_name. This permits writing UNIONs which involve multiple databases. See Identifier Qualifiers for syntax details.

UNION queries cannot be used with aggregate functions.

EXCEPT and UNION have the same operation precedence and INTERSECT has a higher precedence, unless running in Oracle mode, in which case all three have the same precedence.

ALL/DISTINCT

The ALL keyword causes duplicate rows to be preserved. The DISTINCT keyword (the default if the keyword is omitted) causes duplicate rows to be removed by the results.

UNION ALL and UNION DISTINCT can both be present in a query. In this case, UNION DISTINCT will override any UNION ALLs to its left.

MariaDB starting with 10.1.1

Until MariaDB 10.1.1, all UNION ALL statements required the server to create a temporary table. Since MariaDB 10.1.1, the server can in most cases execute UNION ALL without creating a temporary table, improving performance (see MDEV-334).

ORDER BY and LIMIT

Individual SELECTs can contain their own ORDER BY and LIMIT clauses. In this case, the individual queries need to be wrapped between parentheses. However, this does not affect the order of the UNION, so they only are useful to limit the record read by one SELECT.

The UNION can have global ORDER BY and LIMIT clauses, which affect the whole resultset. If the columns retrieved by individual SELECT statements have an alias (AS), the ORDER BY must use that alias, not the real column names.

HIGH_PRIORITY

Specifying a query as HIGH_PRIORITY will not work inside a UNION. If applied to the first SELECT, it will be ignored. Applying to a later SELECT results in a syntax error:

ERROR 1234 (42000): Incorrect usage/placement of 'HIGH_PRIORITY'

SELECT ... INTO ...

Individual SELECTs cannot be written INTO DUMPFILE or INTO OUTFILE. If the last SELECT statement specifies INTO DUMPFILE or INTO OUTFILE, the entire result of the UNION will be written. Placing the clause after any other SELECT will result in a syntax error.

If the result is a single row, SELECT ... INTO @var_name can also be used.

MariaDB starting with 10.4.0

Parentheses

From MariaDB 10.4.0, parentheses can be used to specify precedence. Before this, a syntax error would be returned.

Examples

UNION between tables having different column names:

(SELECT e_name AS name, email FROM employees)
UNION
(SELECT c_name AS name, email FROM customers);

Specifying the UNION's global order and limiting total rows:

(SELECT name, email FROM employees)
UNION
(SELECT name, email FROM customers)
ORDER BY name LIMIT 10;

Adding a constant row:

(SELECT 'John Doe' AS name, 'john.doe@example.net' AS email)
UNION
(SELECT name, email FROM customers);

Differing types:

SELECT CAST('x' AS CHAR(1)) UNION SELECT REPEAT('y',4);
+----------------------+
| CAST('x' AS CHAR(1)) |
+----------------------+
| x                    |
| yyyy                 |
+----------------------+

Returning the results in order of each individual SELECT by use of a sort column:

(SELECT 1 AS sort_column, e_name AS name, email FROM employees)
UNION
(SELECT 2, c_name AS name, email FROM customers) ORDER BY sort_column;

Difference between UNION, EXCEPT and INTERSECT. INTERSECT ALL and EXCEPT ALL are available from MariaDB 10.5.0.

CREATE TABLE seqs (i INT);
INSERT INTO seqs VALUES (1),(2),(2),(3),(3),(4),(5),(6);

SELECT i FROM seqs WHERE i <= 3 UNION SELECT i FROM seqs WHERE i>=3;
+------+
| i    |
+------+
|    1 |
|    2 |
|    3 |
|    4 |
|    5 |
|    6 |
+------+

SELECT i FROM seqs WHERE i <= 3 UNION ALL SELECT i FROM seqs WHERE i>=3;
+------+
| i    |
+------+
|    1 |
|    2 |
|    2 |
|    3 |
|    3 |
|    3 |
|    3 |
|    4 |
|    5 |
|    6 |
+------+

SELECT i FROM seqs WHERE i <= 3 EXCEPT SELECT i FROM seqs WHERE i>=3;
+------+
| i    |
+------+
|    1 |
|    2 |
+------+

SELECT i FROM seqs WHERE i <= 3 EXCEPT ALL SELECT i FROM seqs WHERE i>=3;
+------+
| i    |
+------+
|    1 |
|    2 |
|    2 |
+------+

SELECT i FROM seqs WHERE i <= 3 INTERSECT SELECT i FROM seqs WHERE i>=3;
+------+
| i    |
+------+
|    3 |
+------+

SELECT i FROM seqs WHERE i <= 3 INTERSECT ALL SELECT i FROM seqs WHERE i>=3;
+------+
| i    |
+------+
|    3 |
|    3 |
+------+

Parentheses for specifying precedence, from MariaDB 10.4.0

CREATE OR REPLACE TABLE t1 (a INT);
CREATE OR REPLACE TABLE t2 (b INT);
CREATE OR REPLACE TABLE t3 (c INT);

INSERT INTO t1 VALUES (1),(2),(3),(4);
INSERT INTO t2 VALUES (5),(6);
INSERT INTO t3 VALUES (1),(6);

((SELECT a FROM t1) UNION (SELECT b FROM t2)) INTERSECT (SELECT c FROM t3);
+------+
| a    |
+------+
|    1 |
|    6 |
+------+

(SELECT a FROM t1) UNION ((SELECT b FROM t2) INTERSECT (SELECT c FROM t3));
+------+
| a    |
+------+
|    1 |
|    2 |
|    3 |
|    4 |
|    6 |
+------+

See Also

1.1.1.4.1.2.4 EXCEPT

MariaDB starting with 10.3.0

EXCEPT was introduced in MariaDB 10.3.0.

The result of EXCEPT is all records of the left SELECT result set except records which are in right SELECT result set, i.e. it is subtraction of two result sets. From MariaDB 10.6.1, MINUS is a synonym.

Syntax

SELECT ...
(INTERSECT [ALL | DISTINCT] | EXCEPT [ALL | DISTINCT] | UNION [ALL | DISTINCT]) SELECT ...
[(INTERSECT [ALL | DISTINCT] | EXCEPT [ALL | DISTINCT] | UNION [ALL | DISTINCT]) SELECT ...]
[ORDER BY [column [, column ...]]]
[LIMIT {[offset,] row_count | row_count OFFSET offset}]

Contents

  1. Syntax
    1. Description
      1. Parentheses
      2. ALL/DISTINCT
    2. Examples
    3. See Also

Please note:

  • Brackets for explicit operation precedence are not supported; use a subquery in the FROM clause as a workaround).

Description

MariaDB has supported EXCEPT and INTERSECT in addition to UNION since MariaDB 10.3.

All behavior for naming columns, ORDER BY and LIMIT is the same as for UNION.

EXCEPT implicitly supposes a DISTINCT operation.

The result of EXCEPT is all records of the left SELECT result except records which are in right SELECT result set, i.e. it is subtraction of two result sets.

EXCEPT and UNION have the same operation precedence and INTERSECT has a higher precedence, unless running in Oracle mode, in which case all three have the same precedence.

MariaDB starting with 10.4.0

Parentheses

From MariaDB 10.4.0, parentheses can be used to specify precedence. Before this, a syntax error would be returned.

MariaDB starting with 10.5.0

ALL/DISTINCT

EXCEPT ALL and EXCEPT DISTINCT were introduced in MariaDB 10.5.0. The ALL operator leaves duplicates intact, while the DISTINCT operator removes duplicates. DISTINCT is the default behavior if neither operator is supplied, and the only behavior prior to MariaDB 10.5.

Examples

Show customers which are not employees:

(SELECT e_name AS name, email FROM customers)
EXCEPT
(SELECT c_name AS name, email FROM employees);

Difference between UNION, EXCEPT and INTERSECT. INTERSECT ALL and EXCEPT ALL are available from MariaDB 10.5.0.

CREATE TABLE seqs (i INT);
INSERT INTO seqs VALUES (1),(2),(2),(3),(3),(4),(5),(6);

SELECT i FROM seqs WHERE i <= 3 UNION SELECT i FROM seqs WHERE i>=3;
+------+
| i    |
+------+
|    1 |
|    2 |
|    3 |
|    4 |
|    5 |
|    6 |
+------+

SELECT i FROM seqs WHERE i <= 3 UNION ALL SELECT i FROM seqs WHERE i>=3;
+------+
| i    |
+------+
|    1 |
|    2 |
|    2 |
|    3 |
|    3 |
|    3 |
|    3 |
|    4 |
|    5 |
|    6 |
+------+

SELECT i FROM seqs WHERE i <= 3 EXCEPT SELECT i FROM seqs WHERE i>=3;
+------+
| i    |
+------+
|    1 |
|    2 |
+------+

SELECT i FROM seqs WHERE i <= 3 EXCEPT ALL SELECT i FROM seqs WHERE i>=3;
+------+
| i    |
+------+
|    1 |
|    2 |
|    2 |
+------+

SELECT i FROM seqs WHERE i <= 3 INTERSECT SELECT i FROM seqs WHERE i>=3;
+------+
| i    |
+------+
|    3 |
+------+

SELECT i FROM seqs WHERE i <= 3 INTERSECT ALL SELECT i FROM seqs WHERE i>=3;
+------+
| i    |
+------+
|    3 |
|    3 |
+------+

Parentheses for specifying precedence, from MariaDB 10.4.0

CREATE OR REPLACE TABLE t1 (a INT);
CREATE OR REPLACE TABLE t2 (b INT);
CREATE OR REPLACE TABLE t3 (c INT);

INSERT INTO t1 VALUES (1),(2),(3),(4);
INSERT INTO t2 VALUES (5),(6);
INSERT INTO t3 VALUES (1),(6);

((SELECT a FROM t1) UNION (SELECT b FROM t2)) EXCEPT (SELECT c FROM t3);
+------+
| a    |
+------+
|    2 |
|    3 |
|    4 |
|    5 |
+------+

(SELECT a FROM t1) UNION ((SELECT b FROM t2) EXCEPT (SELECT c FROM t3));
+------+
| a    |
+------+
|    1 |
|    2 |
|    3 |
|    4 |
|    5 |
+------+

See Also

1.1.1.4.1.2.5 INTERSECT

MariaDB starting with 10.3.0

INTERSECT was introduced in MariaDB 10.3.0.

The result of an intersect is the intersection of right and left SELECT results, i.e. only records that are present in both result sets will be included in the result of the operation.

Syntax

SELECT ...
(INTERSECT [ALL | DISTINCT] | EXCEPT [ALL | DISTINCT] | UNION [ALL | DISTINCT]) SELECT ...
[(INTERSECT [ALL | DISTINCT] | EXCEPT [ALL | DISTINCT] | UNION [ALL | DISTINCT]) SELECT ...]
[ORDER BY [column [, column ...]]]
[LIMIT {[offset,] row_count | row_count OFFSET offset}]

Contents

  1. Syntax
  2. Description
    1. Parentheses
    2. ALL/DISTINCT
  3. Examples
  4. See Also

Description

MariaDB has supported INTERSECT (as well as EXCEPT) in addition to UNION since MariaDB 10.3.

All behavior for naming columns, ORDER BY and LIMIT is the same as for UNION.

INTERSECT implicitly supposes a DISTINCT operation.

The result of an intersect is the intersection of right and left SELECT results, i.e. only records that are present in both result sets will be included in the result of the operation.

INTERSECT has higher precedence than UNION and EXCEPT (unless running running in Oracle mode, in which case all three have the same precedence). If possible it will be executed linearly but if not it will be translated to a subquery in the FROM clause:

(select a,b from t1)
union
(select c,d from t2)
intersect
(select e,f from t3)
union
(select 4,4);

will be translated to:

(select a,b from t1)
union
select c,d from
  ((select c,d from t2)
   intersect
   (select e,f from t3)) dummy_subselect
union
(select 4,4)



MariaDB starting with 10.4.0

Parentheses

From MariaDB 10.4.0, parentheses can be used to specify precedence. Before this, a syntax error would be returned.

MariaDB starting with 10.5.0

ALL/DISTINCT

INTERSECT ALL and INTERSECT DISTINCT were introduced in MariaDB 10.5.0. The ALL operator leaves duplicates intact, while the DISTINCT operator removes duplicates. DISTINCT is the default behavior if neither operator is supplied, and the only behavior prior to MariaDB 10.5.

Examples

Show customers which are employees:

(SELECT e_name AS name, email FROM employees)
INTERSECT
(SELECT c_name AS name, email FROM customers);

Difference between UNION, EXCEPT and INTERSECT. INTERSECT ALL and EXCEPT ALL are available from MariaDB 10.5.0.

CREATE TABLE seqs (i INT);
INSERT INTO seqs VALUES (1),(2),(2),(3),(3),(4),(5),(6);

SELECT i FROM seqs WHERE i <= 3 UNION SELECT i FROM seqs WHERE i>=3;
+------+
| i    |
+------+
|    1 |
|    2 |
|    3 |
|    4 |
|    5 |
|    6 |
+------+

SELECT i FROM seqs WHERE i <= 3 UNION ALL SELECT i FROM seqs WHERE i>=3;
+------+
| i    |
+------+
|    1 |
|    2 |
|    2 |
|    3 |
|    3 |
|    3 |
|    3 |
|    4 |
|    5 |
|    6 |
+------+

SELECT i FROM seqs WHERE i <= 3 EXCEPT SELECT i FROM seqs WHERE i>=3;
+------+
| i    |
+------+
|    1 |
|    2 |
+------+

SELECT i FROM seqs WHERE i <= 3 EXCEPT ALL SELECT i FROM seqs WHERE i>=3;
+------+
| i    |
+------+
|    1 |
|    2 |
|    2 |
+------+

SELECT i FROM seqs WHERE i <= 3 INTERSECT SELECT i FROM seqs WHERE i>=3;
+------+
| i    |
+------+
|    3 |
+------+

SELECT i FROM seqs WHERE i <= 3 INTERSECT ALL SELECT i FROM seqs WHERE i>=3;
+------+
| i    |
+------+
|    3 |
|    3 |
+------+

Parentheses for specifying precedence, from MariaDB 10.4.0

CREATE OR REPLACE TABLE t1 (a INT);
CREATE OR REPLACE TABLE t2 (b INT);
CREATE OR REPLACE TABLE t3 (c INT);

INSERT INTO t1 VALUES (1),(2),(3),(4);
INSERT INTO t2 VALUES (5),(6);
INSERT INTO t3 VALUES (1),(6);

((SELECT a FROM t1) UNION (SELECT b FROM t2)) INTERSECT (SELECT c FROM t3);
+------+
| a    |
+------+
|    1 |
|    6 |
+------+

(SELECT a FROM t1) UNION ((SELECT b FROM t2) INTERSECT (SELECT c FROM t3));
+------+
| a    |
+------+
|    1 |
|    2 |
|    3 |
|    4 |
|    6 |
+------+

See Also

1.1.1.4.1.2.6 Precedence Control in Table Operations

MariaDB starting with 10.4.0

Beginning in MariaDB 10.4, you can control the ordering of execution on table operations using parentheses.

Syntax

(  expression )
[ORDER BY [column[, column...]]]
[LIMIT {[offset,] row_count | row_count OFFSET offset}]

Contents

  1. Syntax
  2. Description
  3. Example

Description

Using parentheses in your SQL allows you to control the order of execution for SELECT statements and Table Value Constructor, including UNION, EXCEPT, and INTERSECT operations. MariaDB executes the parenthetical expression before the rest of the statement. You can then use ORDER BY and LIMIT clauses the further organize the result-set.

Note: In practice, the Optimizer may rearrange the exact order in which MariaDB executes different parts of the statement. When it calculates the result-set, however, it returns values as though the parenthetical expression were executed first.

Example

CREATE TABLE test.t1 (num INT);

INSERT INTO test.t1 VALUES (1),(2),(3);

(SELECT * FROM test.t1 
 UNION 
 VALUES (10)) 
INTERSECT 
VALUES (1),(3),(10),(11);
+------+
| num  |
+------+
|    1 |
|    3 |
|   10 |
+------+

((SELECT * FROM test.t1 
  UNION 
  VALUES (10)) 
 INTERSECT 
 VALUES (1),(3),(10),(11)) 
ORDER BY 1 DESC;
+------+
| num  |
+------+
|   10 |
|    3 |
|    1 |
+------+

1.1.1.4.1.2.7 MINUS

MariaDB starting with 10.6.1

MINUS was introduced as a synonym for EXCEPT from MariaDB 10.6.1.

1.1.1.4.1.3 LIMIT

Contents

  1. Description
    1. Multi-Table Updates
    2. GROUP_CONCAT
  2. Examples
  3. See Also

Description

Use the LIMIT clause to restrict the number of returned rows. When you use a single integer n with LIMIT, the first n rows will be returned. Use the ORDER BY clause to control which rows come first. You can also select a number of rows after an offset using either of the following:

LIMIT offset, row_count
LIMIT row_count OFFSET offset

When you provide an offset m with a limit n, the first m rows will be ignored, and the following n rows will be returned.

Executing an UPDATE with the LIMIT clause is not safe for replication. LIMIT 0 is an exception to this rule (see MDEV-6170).

There is a LIMIT ROWS EXAMINED optimization which provides the means to terminate the execution of SELECT statements which examine too many rows, and thus use too many resources. See LIMIT ROWS EXAMINED.

Multi-Table Updates

MariaDB starting with 10.3.2

Until MariaDB 10.3.1, it was not possible to use LIMIT (or ORDER BY) in a multi-table UPDATE statement. This restriction was lifted in MariaDB 10.3.2.

GROUP_CONCAT

MariaDB starting with 10.3.2

Starting from MariaDB 10.3.3, it is possible to use LIMIT with GROUP_CONCAT().

Examples

CREATE TABLE members (name VARCHAR(20));
INSERT INTO members VALUES('Jagdish'),('Kenny'),('Rokurou'),('Immaculada');

SELECT * FROM members;
+------------+
| name       |
+------------+
| Jagdish    |
| Kenny      |
| Rokurou    |
| Immaculada |
+------------+

Select the first two names (no ordering specified):

SELECT * FROM members LIMIT 2;
+---------+
| name    |
+---------+
| Jagdish |
| Kenny   |
+---------+

All the names in alphabetical order:

SELECT * FROM members ORDER BY name;
+------------+
| name       |
+------------+
| Immaculada |
| Jagdish    |
| Kenny      |
| Rokurou    |
+------------+

The first two names, ordered alphabetically:

SELECT * FROM members ORDER BY name LIMIT 2;
+------------+
| name       |
+------------+
| Immaculada |
| Jagdish    |
+------------+

The third name, ordered alphabetically (the first name would be offset zero, so the third is offset two):

SELECT * FROM members ORDER BY name LIMIT 2,1;
+-------+
| name  |
+-------+
| Kenny |
+-------+

From MariaDB 10.3.2, LIMIT can be used in a multi-table update:

CREATE TABLE warehouse (product_id INT, qty INT);
INSERT INTO warehouse VALUES (1,100),(2,100),(3,100),(4,100);

CREATE TABLE store (product_id INT, qty INT);
INSERT INTO store VALUES (1,5),(2,5),(3,5),(4,5);

UPDATE warehouse,store SET warehouse.qty = warehouse.qty-2, store.qty = store.qty+2 
  WHERE (warehouse.product_id = store.product_id AND store.product_id  >= 1) 
    ORDER BY store.product_id DESC LIMIT 2;

SELECT * FROM warehouse;
+------------+------+
| product_id | qty  |
+------------+------+
|          1 |  100 |
|          2 |  100 |
|          3 |   98 |
|          4 |   98 |
+------------+------+

SELECT * FROM store;
+------------+------+
| product_id | qty  |
+------------+------+
|          1 |    5 |
|          2 |    5 |
|          3 |    7 |
|          4 |    7 |
+------------+------+

From MariaDB 10.3.3, LIMIT can be used with GROUP_CONCAT, so, for example, given the following table:

CREATE TABLE d (dd DATE, cc INT);

INSERT INTO d VALUES ('2017-01-01',1);
INSERT INTO d VALUES ('2017-01-02',2);
INSERT INTO d VALUES ('2017-01-04',3);

the following query:

SELECT SUBSTRING_INDEX(GROUP_CONCAT(CONCAT_WS(":",dd,cc) ORDER BY cc DESC),",",1) FROM d;
+----------------------------------------------------------------------------+
| SUBSTRING_INDEX(GROUP_CONCAT(CONCAT_WS(":",dd,cc) ORDER BY cc DESC),",",1) |
+----------------------------------------------------------------------------+
| 2017-01-04:3                                                               |
+----------------------------------------------------------------------------+

can be more simply rewritten as:

SELECT GROUP_CONCAT(CONCAT_WS(":",dd,cc) ORDER BY cc DESC LIMIT 1) FROM d;
+-------------------------------------------------------------+
| GROUP_CONCAT(CONCAT_WS(":",dd,cc) ORDER BY cc DESC LIMIT 1) |
+-------------------------------------------------------------+
| 2017-01-04:3                                                |
+-------------------------------------------------------------+

See Also

1.1.1.4.1.4 ORDER BY

Contents

  1. Description
  2. Examples
  3. See Also

Description

Use the ORDER BY clause to order a resultset, such as that are returned from a SELECT statement. You can specify just a column or use any expression with functions. If you are using the GROUP BY clause, you can use grouping functions in ORDER BY. Ordering is done after grouping.

You can use multiple ordering expressions, separated by commas. Rows will be sorted by the first expression, then by the second expression if they have the same value for the first, and so on.

You can use the keywords ASC and DESC after each ordering expression to force that ordering to be ascending or descending, respectively. Ordering is ascending by default.

You can also use a single integer as the ordering expression. If you use an integer n, the results will be ordered by the nth column in the select expression.

When string values are compared, they are compared as if by the STRCMP function. STRCMP ignores trailing whitespace and may normalize characters and ignore case, depending on the collation in use.

Duplicated entries in the ORDER BY clause are removed.

ORDER BY can also be used to order the activities of a DELETE or UPDATE statement (usually with the LIMIT clause).

MariaDB starting with 10.3.2

Until MariaDB 10.3.1, it was not possible to use ORDER BY (or LIMIT) in a multi-table UPDATE statement. This restriction was lifted in MariaDB 10.3.2.

MariaDB starting with 10.5

From MariaDB 10.5, MariaDB allows packed sort keys and values of non-sorted fields in the sort buffer. This can make filesort temporary files much smaller when VARCHAR, CHAR or BLOBs are used, notably speeding up some ORDER BY sorts.

Examples

CREATE TABLE seq (i INT, x VARCHAR(1));
INSERT INTO seq VALUES (1,'a'), (2,'b'), (3,'b'), (4,'f'), (5,'e');

SELECT * FROM seq ORDER BY i;
+------+------+
| i    | x    |
+------+------+
|    1 | a    |
|    2 | b    |
|    3 | b    |
|    4 | f    |
|    5 | e    |
+------+------+

SELECT * FROM seq ORDER BY i DESC;
+------+------+
| i    | x    |
+------+------+
|    5 | e    |
|    4 | f    |
|    3 | b    |
|    2 | b    |
|    1 | a    |
+------+------+

SELECT * FROM seq ORDER BY x,i;
+------+------+
| i    | x    |
+------+------+
|    1 | a    |
|    2 | b    |
|    3 | b    |
|    5 | e    |
|    4 | f    |
+------+------+

ORDER BY in an UPDATE statement, in conjunction with LIMIT:

UPDATE seq SET x='z' WHERE x='b' ORDER BY i DESC LIMIT 1;

SELECT * FROM seq;
+------+------+
| i    | x    |
+------+------+
|    1 | a    |
|    2 | b    |
|    3 | z    |
|    4 | f    |
|    5 | e    |
+------+------+

From MariaDB 10.3.2, ORDER BY can be used in a multi-table update:

CREATE TABLE warehouse (product_id INT, qty INT);
INSERT INTO warehouse VALUES (1,100),(2,100),(3,100),(4,100);

CREATE TABLE store (product_id INT, qty INT);
INSERT INTO store VALUES (1,5),(2,5),(3,5),(4,5);

UPDATE warehouse,store SET warehouse.qty = warehouse.qty-2, store.qty = store.qty+2 
  WHERE (warehouse.product_id = store.product_id AND store.product_id  >= 1) 
    ORDER BY store.product_id DESC LIMIT 2;

SELECT * FROM warehouse;
+------------+------+
| product_id | qty  |
+------------+------+
|          1 |  100 |
|          2 |  100 |
|          3 |   98 |
|          4 |   98 |
+------------+------+

SELECT * FROM store;
+------------+------+
| product_id | qty  |
+------------+------+
|          1 |    5 |
|          2 |    5 |
|          3 |    7 |
|          4 |    7 |
+------------+------+

See Also

1.1.1.4.1.5 GROUP BY

Contents

  1. WITH ROLLUP
  2. GROUP BY Examples
  3. See Also

Use the GROUP BY clause in a SELECT statement to group rows together that have the same value in one or more column, or the same computed value using expressions with any functions and operators except grouping functions. When you use a GROUP BY clause, you will get a single result row for each group of rows that have the same value for the expression given in GROUP BY.

When grouping rows, grouping values are compared as if by the = operator. For string values, the = operator ignores trailing whitespace and may normalize characters and ignore case, depending on the collation in use.

You can use any of the grouping functions in your select expression. Their values will be calculated based on all the rows that have been grouped together for each result row. If you select a non-grouped column or a value computed from a non-grouped column, it is undefined which row the returned value is taken from. This is not permitted if the ONLY_FULL_GROUP_BY SQL_MODE is used.

You can use multiple expressions in the GROUP BY clause, separated by commas. Rows are grouped together if they match on each of the expressions.

You can also use a single integer as the grouping expression. If you use an integer n, the results will be grouped by the nth column in the select expression.

The WHERE clause is applied before the GROUP BY clause. It filters non-aggregated rows before the rows are grouped together. To filter grouped rows based on aggregate values, use the HAVING clause. The HAVING clause takes any expression and evaluates it as a boolean, just like the WHERE clause. You can use grouping functions in the HAVING clause. As with the select expression, if you reference non-grouped columns in the HAVING clause, the behavior is undefined.

By default, if a GROUP BY clause is present, the rows in the output will be sorted by the expressions used in the GROUP BY. You can also specify ASC or DESC (ascending, descending) after those expressions, like in ORDER BY. The default is ASC.

If you want the rows to be sorted by another field, you can add an explicit ORDER BY. If you don't want the result to be ordered, you can add ORDER BY NULL.

WITH ROLLUP

The WITH ROLLUP modifer adds extra rows to the resultset that represent super-aggregate summaries. For a full description with examples, see SELECT WITH ROLLUP.

GROUP BY Examples

Consider the following table that records how many times each user has played and won a game:

CREATE TABLE plays (name VARCHAR(16), plays INT, wins INT);
INSERT INTO plays VALUES 
  ("John", 20, 5), 
  ("Robert", 22, 8), 
  ("Wanda", 32, 8), 
  ("Susan", 17, 3);

Get a list of win counts along with a count:

SELECT wins, COUNT(*) FROM plays GROUP BY wins;
+------+----------+
| wins | COUNT(*) |
+------+----------+
|    3 |        1 |
|    5 |        1 |
|    8 |        2 |
+------+----------+
3 rows in set (0.00 sec)

The GROUP BY expression can be a computed value, and can refer back to an identifer specified with AS. Get a list of win averages along with a count:

SELECT (wins / plays) AS winavg, COUNT(*) FROM plays GROUP BY winavg;
+--------+----------+
| winavg | COUNT(*) |
+--------+----------+
| 0.1765 |        1 |
| 0.2500 |        2 |
| 0.3636 |        1 |
+--------+----------+
3 rows in set (0.00 sec)

You can use any grouping function in the select expression. For each win average as above, get a list of the average play count taken to get that average:

SELECT (wins / plays) AS winavg, AVG(plays) FROM plays 
  GROUP BY winavg;
+--------+------------+
| winavg | AVG(plays) |
+--------+------------+
| 0.1765 |    17.0000 |
| 0.2500 |    26.0000 |
| 0.3636 |    22.0000 |
+--------+------------+
3 rows in set (0.00 sec)

You can filter on aggregate information using the HAVING clause. The HAVING clause is applied after GROUP BY and allows you to filter on aggregate data that is not available to the WHERE clause. Restrict the above example to results that involve an average number of plays over 20:

SELECT (wins / plays) AS winavg, AVG(plays) FROM plays 
  GROUP BY winavg HAVING AVG(plays) > 20;
+--------+------------+
| winavg | AVG(plays) |
+--------+------------+
| 0.2500 |    26.0000 |
| 0.3636 |    22.0000 |
+--------+------------+
2 rows in set (0.00 sec)

See Also

1.1.1.4.1.6 Common Table Expressions

MariaDB starting with 10.2.1

Common table expressions were introduced in MariaDB 10.2.1.

There are 1 related questions.

1.1.1.4.1.6.1 WITH

MariaDB starting with 10.2.1

Common Table Expressions were introduced in MariaDB 10.2.1.

Syntax

WITH [RECURSIVE] table_reference [(columns_list)] AS  (
  SELECT ...
)
[CYCLE cycle_column_list RESTRICT]
SELECT ...

Contents

  1. Syntax
  2. Description
    1. CYCLE ... RESTRICT
  3. Examples
  4. See Also

Description

The WITH keyword signifies a Common Table Expression (CTE). It allows you to refer to a subquery expression many times in a query, as if having a temporary table that only exists for the duration of a query.

There are two kinds of CTEs:

You can use table_reference as any normal table in the external SELECT part. You can also use WITH in subqueries, as well as with EXPLAIN and SELECT.

Poorly-formed recursive CTEs can in theory cause infinite loops. The max_recursive_iterations system variable limits the number of recursions.

CYCLE ... RESTRICT

MariaDB starting with 10.5.2

The CYCLE clause enables CTE cycle detection, avoiding excessive or infinite loops, MariaDB supports a relaxed, non-standard grammar.

The SQL Standard permits a CYCLE clause, as follows:

WITH RECURSIVE ... (
  ...
)
CYCLE <cycle column list>
SET <cycle mark column> TO <cycle mark value> DEFAULT <non-cycle mark value>
USING <path column>

where all clauses are mandatory.

MariaDB does not support this, but from 10.5.2 permits a non-standard relaxed grammar, as follows:

WITH RECURSIVE ... (
  ...
)
CYCLE <cycle column list> RESTRICT

With the use of CYCLE ... RESTRICT it makes no difference whether the CTE uses UNION ALL or UNION DISTINCT anymore. UNION ALL means "all rows, but without cycles", which is exactly what the CYCLE clause enables. And UNION DISTINCT means all rows should be different, which, again, is what will happen — as uniqueness is enforced over a subset of columns, complete rows will automatically all be different.

Examples

Below is an example with the WITH at the top level:

WITH t AS (SELECT a FROM t1 WHERE b >= 'c') 
  SELECT * FROM t2, t WHERE t2.c = t.a;

The example below uses WITH in a subquery:

SELECT t1.a, t1.b FROM t1, t2
  WHERE t1.a > t2.c 
     AND t2.c IN(WITH t AS (SELECT * FROM t1 WHERE t1.a < 5)
                SELECT t2.c FROM t2, t WHERE t2.c = t.a);

Below is an example of a Recursive CTE:

WITH RECURSIVE ancestors AS 
 ( SELECT * FROM folks
   WHERE name="Alex"
   UNION
   SELECT f.*
   FROM folks AS f, ancestors AS a
   WHERE f.id = a.father OR f.id = a.mother )
SELECT * FROM ancestors;

Take the following structure, and data,

CREATE TABLE t1 (from_ int, to_ int);
INSERT INTO t1 VALUES (1,2), (1,100), (2,3), (3,4), (4,1);
SELECT * FROM t1;
+-------+------+
| from_ | to_  |
+-------+------+
|     1 |    2 |
|     1 |  100 |
|     2 |    3 |
|     3 |    4 |
|     4 |    1 |
+-------+------+

Given the above, the following query would theoretically result in an infinite loop due to the last record in t1 (note that max_recursive_iterations is set to 10 for the purposes of this example, to avoid the excessive number of cycles):

SET max_recursive_iterations=10;

WITH RECURSIVE cte (depth, from_, to_) AS ( 
  SELECT 0,1,1 UNION DISTINCT SELECT depth+1, t1.from_, t1.to_ 
    FROM t1, cte  WHERE t1.from_ = cte.to_ 
) 
SELECT * FROM cte;
+-------+-------+------+
| depth | from_ | to_  |
+-------+-------+------+
|     0 |     1 |    1 |
|     1 |     1 |    2 |
|     1 |     1 |  100 |
|     2 |     2 |    3 |
|     3 |     3 |    4 |
|     4 |     4 |    1 |
|     5 |     1 |    2 |
|     5 |     1 |  100 |
|     6 |     2 |    3 |
|     7 |     3 |    4 |
|     8 |     4 |    1 |
|     9 |     1 |    2 |
|     9 |     1 |  100 |
|    10 |     2 |    3 |
+-------+-------+------+

However, the CYCLE ... RESTRICT clause (from MariaDB 10.5.2) can overcome this:

WITH RECURSIVE cte (depth, from_, to_) AS ( 
  SELECT 0,1,1 UNION SELECT depth+1, t1.from_, t1.to_ 
    FROM t1, cte WHERE t1.from_ = cte.to_ 
) 
CYCLE from_, to_ RESTRICT 
SELECT * FROM cte;
+-------+-------+------+
| depth | from_ | to_  |
+-------+-------+------+
|     0 |     1 |    1 |
|     1 |     1 |    2 |
|     1 |     1 |  100 |
|     2 |     2 |    3 |
|     3 |     3 |    4 |
|     4 |     4 |    1 |
+-------+-------+------+

See Also

1.1.1.4.1.6.2 Non-Recursive Common Table Expressions Overview

Contents

  1. Non-Recursive CTEs
    1. A CTE referencing Another CTE
    2. Multiple Uses of a CTE

Common Table Expressions (CTEs) are a standard SQL feature, and are essentially temporary named result sets. There are two kinds of CTEs: Non-Recursive, which this article covers; and Recursive.

MariaDB starting with 10.2.1

Common table expressions were introduced in MariaDB 10.2.1.

Non-Recursive CTEs

The WITH keyword signifies a CTE. It is given a name, followed by a body (the main query) as follows: cte_syntax

CTEs are similar to derived tables. For example

WITH engineers AS 
   ( SELECT * FROM employees
     WHERE dept = 'Engineering' )

SELECT * FROM engineers
WHERE ...

SELECT * FROM
   ( SELECT * FROM employees
     WHERE dept = 'Engineering' ) AS engineers
WHERE
...

A non-recursive CTE is basically a query-local VIEW. There are several advantages and caveats to them. The syntax is more readable than nested FROM (SELECT ...). A CTE can refer to another and it can be referenced from multiple places.

A CTE referencing Another CTE

Using this format makes for a more readable SQL than a nested FROM(SELECT ...) clause. Below is an example of this:

WITH engineers AS (
SELECT * FROM employees
WHERE dept IN('Development','Support') ),
eu_engineers AS ( SELECT * FROM engineers WHERE country IN('NL',...) )
SELECT
...
FROM eu_engineers;

Multiple Uses of a CTE

This can be an 'anti-self join', for example:

WITH engineers AS (
SELECT * FROM employees
WHERE dept IN('Development','Support') )

SELECT * FROM engineers E1
WHERE NOT EXISTS
   (SELECT 1 FROM engineers E2
    WHERE E2.country=E1.country
    AND E2.name <> E1.name );

Or, for year-over-year comparisons, for example:

WITH sales_product_year AS (
SELECT product, YEAR(ship_date) AS year,
SUM(price) AS total_amt
FROM item_sales
GROUP BY product, year )

SELECT *
FROM sales_product_year CUR,
sales_product_year PREV,
WHERE CUR.product=PREV.product 
AND  CUR.year=PREV.year + 1 
AND CUR.total_amt > PREV.total_amt

Another use is to compare individuals against their group. Below is an example of how this might be executed:

WITH sales_product_year AS (
SELECT product,
YEAR(ship_date) AS year,
SUM(price) AS total_amt
FROM item_sales
GROUP BY product, year
)

SELECT * 
FROM sales_product_year S1
WHERE
total_amt > 
    (SELECT 0.1 * SUM(total_amt)
     FROM sales_product_year S2
     WHERE S2.year = S1.year)

1.1.1.4.1.6.3 Recursive Common Table Expressions Overview

MariaDB starting with 10.2.2

Recursive Common Table Expressions have been supported since MariaDB 10.2.2.

Contents

  1. Syntax example
  2. Computation
  3. Summary so far
  4. CAST to avoid truncating data
  5. Examples
    1. Transitive closure - determining bus destinations
    2. Computing paths - determining bus routes
    3. CAST to avoid data truncation

Common Table Expressions (CTEs) are a standard SQL feature, and are essentially temporary named result sets. CTEs first appeared in the SQL standard in 1999, and the first implementations began appearing in 2007.

There are two kinds of CTEs:

SQL is generally poor at recursive structures.

trees_and_graphs

CTEs permit a query to reference itself. A recursive CTE will repeatedly execute subsets of the data until it obtains the complete result set. This makes it particularly useful for handing hierarchical or tree-structured data. max_recursive_iterations avoids infinite loops.

Syntax example

WITH RECURSIVE signifies a recursive CTE. It is given a name, followed by a body (the main query) as follows:

rcte_syntax

cte_syntax

Computation

Given the following structure: rcte_computation

First execute the anchor part of the query: rcte1

Next, execute the recursive part of the query: rcte_computation_2

rcte_computation_2b

rcte_computation_3

rcte_computation_3b

rcte_computation_4

Summary so far

with recursive R as (
  select anchor_data
  union [all]
  select recursive_part
  from R, ...
)
select ...
  1. Compute anchor_data
  2. Compute recursive_part to get the new data
  3. if (new data is non-empty) goto 2;

CAST to avoid truncating data

As currently implemented by MariaDB and by the SQL Standard, data may be truncated if not correctly cast. It is necessary to CAST the column to the correct width if the CTE's recursive part produces wider values for a column than the CTE's nonrecursive part. Some other DBMS give an error in this situation, and MariaDB's behavior may change in future - see MDEV-12325. See the examples below.

Examples

Transitive closure - determining bus destinations

Sample data:

tc_1

CREATE TABLE bus_routes (origin varchar(50), dst varchar(50));
INSERT INTO bus_routes VALUES 
  ('New York', 'Boston'), 
  ('Boston', 'New York'), 
  ('New York', 'Washington'), 
  ('Washington', 'Boston'), 
  ('Washington', 'Raleigh');

Now, we want to return the bus destinations with New York as the origin:

WITH RECURSIVE bus_dst as ( 
    SELECT origin as dst FROM bus_routes WHERE origin='New York' 
  UNION
    SELECT bus_routes.dst FROM bus_routes JOIN bus_dst ON bus_dst.dst= bus_routes.origin 
) 
SELECT * FROM bus_dst;
+------------+
| dst        |
+------------+
| New York   |
| Boston     |
| Washington |
| Raleigh    |
+------------+

The above example is computed as follows:

First, the anchor data is calculated:

  • Starting from New York
  • Boston and Washington are added

Next, the recursive part:

  • Starting from Boston and then Washington
  • Raleigh is added
  • UNION excludes nodes that are already present.

Computing paths - determining bus routes

This time, we are trying to get bus routes such as “New York -> Washington -> Raleigh”.

Using the same sample data as the previous example:

WITH RECURSIVE paths (cur_path, cur_dest) AS (
    SELECT origin, origin FROM bus_routes WHERE origin='New York' 
  UNION
    SELECT CONCAT(paths.cur_path, ',', bus_routes.dst), bus_routes.dst 
     FROM paths
     JOIN bus_routes 
       ON paths.cur_dest = bus_routes.origin AND 
         NOT FIND_IN_SET(bus_routes.dst, paths.cur_path)
) 
SELECT * FROM paths;
+-----------------------------+------------+
| cur_path                    | cur_dest   |
+-----------------------------+------------+
| New York                    | New York   |
| New York,Boston             | Boston     |
| New York,Washington         | Washington |
| New York,Washington,Boston  | Boston     |
| New York,Washington,Raleigh | Raleigh    |
+-----------------------------+------------+

CAST to avoid data truncation

In the following example, data is truncated because the results are not specifically cast to a wide enough type:

WITH RECURSIVE tbl AS (
  SELECT NULL AS col
  UNION
  SELECT "THIS NEVER SHOWS UP" AS col FROM tbl
)
SELECT col FROM tbl
+------+
| col  |
+------+
| NULL |
|      |
+------+

Explicitly use CAST to overcome this:

WITH RECURSIVE tbl AS (
  SELECT CAST(NULL AS CHAR(50)) AS col
  UNION SELECT "THIS NEVER SHOWS UP" AS col FROM tbl
)  
SELECT * FROM tbl;
+---------------------+
| col                 |
+---------------------+
| NULL                |
| THIS NEVER SHOWS UP |
+---------------------+

1.1.1.4.1.7 SELECT WITH ROLLUP

Contents

  1. Syntax
  2. Description
  3. Examples
  4. See Also

Syntax

See SELECT for the full syntax.

Description

The WITH ROLLUP modifier adds extra rows to the resultset that represent super-aggregate summaries. The super-aggregated column is represented by a NULL value. Multiple aggregates over different columns will be added if there are multiple GROUP BY columns.

The LIMIT clause can be used at the same time, and is applied after the WITH ROLLUP rows have been added.

WITH ROLLUP cannot be used with ORDER BY. Some sorting is still possible by using ASC or DESC clauses with the GROUP BY column, although the super-aggregate rows will always be added last.

Examples

These examples use the following sample table

CREATE TABLE booksales ( 
  country VARCHAR(35), genre ENUM('fiction','non-fiction'), year YEAR, sales INT);

INSERT INTO booksales VALUES
  ('Senegal','fiction',2014,12234), ('Senegal','fiction',2015,15647),
  ('Senegal','non-fiction',2014,64980), ('Senegal','non-fiction',2015,78901),
  ('Paraguay','fiction',2014,87970), ('Paraguay','fiction',2015,76940),
  ('Paraguay','non-fiction',2014,8760), ('Paraguay','non-fiction',2015,9030);

The addition of the WITH ROLLUP modifier in this example adds an extra row that aggregates both years:

SELECT year, SUM(sales) FROM booksales GROUP BY year;
+------+------------+
| year | SUM(sales) |
+------+------------+
| 2014 |     173944 |
| 2015 |     180518 |
+------+------------+
2 rows in set (0.08 sec)

SELECT year, SUM(sales) FROM booksales GROUP BY year WITH ROLLUP;
+------+------------+
| year | SUM(sales) |
+------+------------+
| 2014 |     173944 |
| 2015 |     180518 |
| NULL |     354462 |
+------+------------+

In the following example, each time the genre, the year or the country change, another super-aggregate row is added:

SELECT country, year, genre, SUM(sales) 
  FROM booksales GROUP BY country, year, genre;
+----------+------+-------------+------------+
| country  | year | genre       | SUM(sales) |
+----------+------+-------------+------------+
| Paraguay | 2014 | fiction     |      87970 |
| Paraguay | 2014 | non-fiction |       8760 |
| Paraguay | 2015 | fiction     |      76940 |
| Paraguay | 2015 | non-fiction |       9030 |
| Senegal  | 2014 | fiction     |      12234 |
| Senegal  | 2014 | non-fiction |      64980 |
| Senegal  | 2015 | fiction     |      15647 |
| Senegal  | 2015 | non-fiction |      78901 |
+----------+------+-------------+------------+

SELECT country, year, genre, SUM(sales) 
  FROM booksales GROUP BY country, year, genre WITH ROLLUP;
+----------+------+-------------+------------+
| country  | year | genre       | SUM(sales) |
+----------+------+-------------+------------+
| Paraguay | 2014 | fiction     |      87970 |
| Paraguay | 2014 | non-fiction |       8760 |
| Paraguay | 2014 | NULL        |      96730 |
| Paraguay | 2015 | fiction     |      76940 |
| Paraguay | 2015 | non-fiction |       9030 |
| Paraguay | 2015 | NULL        |      85970 |
| Paraguay | NULL | NULL        |     182700 |
| Senegal  | 2014 | fiction     |      12234 |
| Senegal  | 2014 | non-fiction |      64980 |
| Senegal  | 2014 | NULL        |      77214 |
| Senegal  | 2015 | fiction     |      15647 |
| Senegal  | 2015 | non-fiction |      78901 |
| Senegal  | 2015 | NULL        |      94548 |
| Senegal  | NULL | NULL        |     171762 |
| NULL     | NULL | NULL        |     354462 |
+----------+------+-------------+------------+

The LIMIT clause, applied after WITH ROLLUP:

SELECT country, year, genre, SUM(sales) 
  FROM booksales GROUP BY country, year, genre WITH ROLLUP LIMIT 4;
+----------+------+-------------+------------+
| country  | year | genre       | SUM(sales) |
+----------+------+-------------+------------+
| Paraguay | 2014 | fiction     |      87970 |
| Paraguay | 2014 | non-fiction |       8760 |
| Paraguay | 2014 | NULL        |      96730 |
| Paraguay | 2015 | fiction     |      76940 |
+----------+------+-------------+------------+

Sorting by year descending:

SELECT country, year, genre, SUM(sales) 
  FROM booksales GROUP BY country, year DESC, genre WITH ROLLUP;
+----------+------+-------------+------------+
| country  | year | genre       | SUM(sales) |
+----------+------+-------------+------------+
| Paraguay | 2015 | fiction     |      76940 |
| Paraguay | 2015 | non-fiction |       9030 |
| Paraguay | 2015 | NULL        |      85970 |
| Paraguay | 2014 | fiction     |      87970 |
| Paraguay | 2014 | non-fiction |       8760 |
| Paraguay | 2014 | NULL        |      96730 |
| Paraguay | NULL | NULL        |     182700 |
| Senegal  | 2015 | fiction     |      15647 |
| Senegal  | 2015 | non-fiction |      78901 |
| Senegal  | 2015 | NULL        |      94548 |
| Senegal  | 2014 | fiction     |      12234 |
| Senegal  | 2014 | non-fiction |      64980 |
| Senegal  | 2014 | NULL        |      77214 |
| Senegal  | NULL | NULL        |     171762 |
| NULL     | NULL | NULL        |     354462 |
+----------+------+-------------+------------+

See Also

1.1.1.4.1.8 SELECT INTO OUTFILE

Syntax

SELECT ... INTO OUTFILE 'file_name'
        [CHARACTER SET charset_name]
        [export_options]

export_options:
    [{FIELDS | COLUMNS}
        [TERMINATED BY 'string']
        [[OPTIONALLY] ENCLOSED BY 'char']
        [ESCAPED BY 'char']
    ]
    [LINES
        [STARTING BY 'string']
        [TERMINATED BY 'string']
    ]

Contents

  1. Syntax
  2. Description
    1. Character-sets
  3. Example
  4. See Also

Description

SELECT INTO OUTFILE writes the resulting rows to a file, and allows the use of column and row terminators to specify a particular output format. The default is to terminate fields with tabs (\t) and lines with newlines (\n).

The file must not exist. It cannot be overwritten. A user needs the FILE privilege to run this statement. Also, MariaDB needs permission to write files in the specified location. If the secure_file_priv system variable is set to a non-empty directory name, the file can only be written to that directory.

The LOAD DATA INFILE statement complements SELECT INTO OUTFILE.

Character-sets

The CHARACTER SET clause specifies the character set in which the results are to be written. Without the clause, no conversion takes place (the binary character set). In this case, if there are multiple character sets, the output will contain these too, and may not easily be able to be reloaded.

In cases where you have two servers using different character-sets, using SELECT INTO OUTFILE to transfer data from one to the other can have unexpected results. To ensure that MariaDB correctly interprets the escape sequences, use the CHARACTER SET clause on both the SELECT INTO OUTFILE statement and the subsequent LOAD DATA INFILE statement.

Example

The following example produces a file in the CSV format:

SELECT customer_id, firstname, surname INTO OUTFILE '/exportdata/customers.txt'
  FIELDS TERMINATED BY ',' OPTIONALLY ENCLOSED BY '"'
  LINES TERMINATED BY '\n'
  FROM customers;

See Also

1.1.1.4.1.9 SELECT INTO DUMPFILE

Contents

  1. Syntax
  2. Description
  3. Example
  4. See Also

Syntax

SELECT ... INTO DUMPFILE 'file_path'

Description

SELECT ... INTO DUMPFILE is a SELECT clause which writes the resultset into a single unformatted row, without any separators, in a file. The results will not be returned to the client.

file_path can be an absolute path, or a relative path starting from the data directory. It can only be specified as a string literal, not as a variable. However, the statement can be dynamically composed and executed as a prepared statement to work around this limitation.

This statement is binary-safe and so is particularly useful for writing BLOB values to file. It can be used, for example, to copy an image or an audio document from the database to a file. SELECT ... INTO FILE can be used to save a text file.

The file must not exist. It cannot be overwritten. A user needs the FILE privilege to run this statement. Also, MariaDB needs permission to write files in the specified location. If the secure_file_priv system variable is set to a non-empty directory name, the file can only be written to that directory.

Since MariaDB 5.1, the character_set_filesystem system variable has controlled interpretation of file names that are given as literal strings.

Example

SELECT _utf8'Hello world!' INTO DUMPFILE '/tmp/world';

SELECT LOAD_FILE('/tmp/world') AS world;
+--------------+
| world        |
+--------------+
| Hello world! |
+--------------+

See Also

1.1.1.4.1.10 FOR UPDATE

InnoDB supports row-level locking. Selected rows can be locked using LOCK IN SHARE MODE or FOR UPDATE. In both cases, a lock is acquired on the rows read by the query, and it will be released when the current transaction is committed.

The FOR UPDATE clause of SELECT applies only when autocommit is set to 0 or the SELECT is enclosed in a transaction. A lock is acquired on the rows, and other transactions are prevented from writing the rows, acquire locks, and from reading them (unless their isolation level is READ UNCOMMITTED).

If autocommit is set to 1, the LOCK IN SHARE MODE and FOR UPDATE clauses have no effect.

If the isolation level is set to SERIALIZABLE, all plain SELECT statements are converted to SELECT ... LOCK IN SHARE MODE.

Example

SELECT * FROM trans WHERE period=2001 FOR UPDATE;

See Also

1.1.1.4.1.11 LOCK IN SHARE MODE

InnoDB supports row-level locking. Selected rows can be locked using LOCK IN SHARE MODE or FOR UPDATE. In both cases, a lock is acquired on the rows read by the query, and it will be released when the current transaction is committed.

When LOCK IN SHARE MODE is specified in a SELECT statement, MariaDB will wait until all transactions that have modified the rows are committed. Then, a write lock is acquired. All transactions can read the rows, but if they want to modify them, they have to wait until your transaction is committed.

If autocommit is set to 1, the LOCK IN SHARE MODE and FOR UPDATE clauses have no effect.

See Also

1.1.1.4.1.12 Optimizer Hints

Optimizer hints

There are some options available in SELECT to affect the execution plan. These are known as optimizer hints.

HIGH PRIORITY

HIGH_PRIORITY gives the statement a higher priority. If the table is locked, high priority SELECTs will be executed as soon as the lock is released, even if other statements are queued. HIGH_PRIORITY applies only if the storage engine only supports table-level locking (MyISAM, MEMORY, MERGE). See HIGH_PRIORITY and LOW_PRIORITY clauses for details.

SQL_CACHE / SQL_NO_CACHE

If the query_cache_type system variable is set to 2 or DEMAND, and the current statement is cacheable, SQL_CACHE causes the query to be cached and SQL_NO_CACHE causes the query not to be cached. For UNIONs, SQL_CACHE or SQL_NO_CACHE should be specified for the first query. See also The Query Cache for more detail and a list of the types of statements that aren't cacheable.

SQL_BUFFER_RESULT

SQL_BUFFER_RESULT forces the optimizer to use a temporary table to process the result. This is useful to free locks as soon as possible.

SQL_SMALL_RESULT / SQL_BIG_RESULT

SQL_SMALL_RESULT and SQL_BIG_RESULT tell the optimizer whether the result is very big or not. Usually, GROUP BY and DISTINCT operations are performed using a temporary table. Only if the result is very big, using a temporary table is not convenient. The optimizer automatically knows if the result is too big, but you can force the optimizer to use a temporary table with SQL_SMALL_RESULT, or avoid the temporary table using SQL_BIG_RESULT.

STRAIGHT_JOIN

STRAIGHT_JOIN applies to the JOIN queries, and tells the optimizer that the tables must be read in the order they appear in the SELECT. For const and system table this options is sometimes ignored.

SQL_CALC_FOUND_ROWS

SQL_CALC_FOUND_ROWS is only applied when using the LIMIT clause. If this option is used, MariaDB will count how many rows would match the query, without the LIMIT clause. That number can be retrieved in the next query, using FOUND_ROWS().

USE/FORCE/IGNORE INDEX

USE INDEX, FORCE INDEX and IGNORE INDEX constrain the query planning to a specific index.

For further information about some of these options, see How to force query plans.

1.1.1.4.1.13 PROCEDURE

The PROCEDURE clause of SELECT passes the whole result set to a Procedure which will process it. These Procedures are not Stored Procedures, and can only be written in the C language, so it is necessary to recompile the server.

Currently, the only available procedure is ANALYSE, which examines the resultset and suggests the optimal datatypes for each column. It is defined in the sql/sql_analyse.cc file, and can be used as an example to create more Procedures.

This clause cannot be used in a view's definition.

See Also

1.1.1.4.1.14 HANDLER

1.1.1.4.1.15 DUAL

Description

You are allowed to specify DUAL as a dummy table name in situations where no tables are referenced, such as the following SELECT statement:

SELECT 1 + 1 FROM DUAL;
+-------+
| 1 + 1 |
+-------+
|     2 |
+-------+

DUAL is purely for the convenience of people who require that all SELECT statements should have FROM and possibly other clauses. MariaDB ignores the clauses. MariaDB does not require FROM DUAL if no tables are referenced.

FROM DUAL could be used when you only SELECT computed values, but require a WHERE clause, perhaps to test that a script correctly handles empty resultsets:

SELECT 1 FROM DUAL WHERE FALSE;
Empty set (0.00 sec)

See Also

1.1.1.4.1.16 SELECT ... OFFSET ... FETCH

MariaDB starting with 10.6.0

SELECT ... OFFSET ... FETCH was introduced in MariaDB 10.6.

Syntax

OFFSET start { ROW | ROWS }
FETCH { FIRST | NEXT } [ count ] { ROW | ROWS } { ONLY | WITH TIES }

Description

The OFFSET clause allows one to return only those elements of a resultset that come after a specified offset. The FETCH clause specifies the number of rows to return, while ONLY or WITH TIES specifies whether or not to also return any further results that tie for last place according to the ordered resultset.

Either the singular ROW or the plural ROWS can be used after the OFFSET and FETCH clauses; the choice has no impact on the results.

In the case of WITH TIES, an ORDER BY clause is required, otherwise an ERROR will be returned.

SELECT i FROM t1 FETCH FIRST 2 ROWS WITH TIES;
ERROR 4180 (HY000): FETCH ... WITH TIES requires ORDER BY clause to be present

Examples

Given a table with 6 rows:

CREATE OR REPLACE TABLE t1 (i INT);
INSERT INTO t1 VALUES (1),(2),(3),(4), (4), (5);
SELECT i FROM t1 ORDER BY i ASC;
+------+
| i    |
+------+
|    1 |
|    2 |
|    3 |
|    4 |
|    4 |
|    5 |
+------+

OFFSET 2 allows one to skip the first two results.

SELECT i FROM t1 ORDER BY i ASC OFFSET 2 ROWS;
+------+
| i    |
+------+
|    3 |
|    4 |
|    4 |
|    5 |
+------+

FETCH FIRST 3 ROWS ONLY limits the results to three rows only

SELECT i FROM t1 ORDER BY i ASC OFFSET 1 ROWS FETCH FIRST 3 ROWS ONLY;
+------+
| i    |
+------+
|    2 |
|    3 |
|    4 |
+------+

The same outcome can also be achieved with the LIMIT clause:

SELECT i FROM t1 ORDER BY i ASC LIMIT 3 OFFSET 1;
+------+
| i    |
+------+
|    2 |
|    3 |
|    4 |
+------+

WITH TIES ensures the tied result 4 is also returned.

SELECT i FROM t1 ORDER BY i ASC OFFSET 1 ROWS FETCH FIRST 3 ROWS WITH TIES;
+------+
| i    |
+------+
|    2 |
|    3 |
|    4 |
|    4 |
+------+

See Also

1.1.1.4.2 Inserting & Loading Data

The INSERT statement is the primary SQL statement for adding data into a table in MariaDB.

There are 3 related questions.

1.1.1.4.2.1 INSERT

Syntax

INSERT [LOW_PRIORITY | DELAYED | HIGH_PRIORITY] [IGNORE]
 [INTO] tbl_name [PARTITION (partition_list)] [(col,...)]
 {VALUES | VALUE} ({expr | DEFAULT},...),(...),...
 [ ON DUPLICATE KEY UPDATE
   col=expr
     [, col=expr] ... ] [RETURNING select_expr 
      [, select_expr ...]]

Or:

INSERT [LOW_PRIORITY | DELAYED | HIGH_PRIORITY] [IGNORE]
    [INTO] tbl_name [PARTITION (partition_list)]
    SET col={expr | DEFAULT}, ...
    [ ON DUPLICATE KEY UPDATE
      col=expr
        [, col=expr] ... ] [RETURNING select_expr 
      [, select_expr ...]]

Or:

INSERT [LOW_PRIORITY | HIGH_PRIORITY] [IGNORE]
    [INTO] tbl_name [PARTITION (partition_list)] [(col,...)]
    SELECT ...
    [ ON DUPLICATE KEY UPDATE
      col=expr
        [, col=expr] ... ] [RETURNING select_expr 
      [, select_expr ...]]

Contents

  1. Syntax
  2. INSERT DELAYED
  3. HIGH PRIORITY and LOW PRIORITY
  4. Defaults and Duplicate Values
  5. INSERT IGNORE
  6. INSERT ON DUPLICATE KEY UPDATE
  7. Examples
  8. INSERT ... RETURNING
    1. Examples
  9. See Also

The INSERT statement is used to insert new rows into an existing table. The INSERT ... VALUES and INSERT ... SET forms of the statement insert rows based on explicitly specified values. The INSERT ... SELECT form inserts rows selected from another table or tables. INSERT ... SELECT is discussed further in the INSERT ... SELECT article.

The table name can be specified in the form db_name.tbl_name or, if a default database is selected, in the form tbl_name (see Identifier Qualifiers). This allows to use INSERT ... SELECT to copy rows between different databases.

The PARTITION clause can be used in both the INSERT and the SELECT part. See Partition Pruning and Selection for details.

MariaDB starting with 10.5

The RETURNING clause was introduced in MariaDB 10.5.

The columns list is optional. It specifies which values are explicitly inserted, and in which order. If this clause is not specified, all values must be explicitly specified, in the same order they are listed in the table definition.

The list of value follow the VALUES or VALUE keyword (which are interchangeable, regardless how much values you want to insert), and is wrapped by parenthesis. The values must be listed in the same order as the columns list. It is possible to specify more than one list to insert more than one rows with a single statement. If many rows are inserted, this is a speed optimization.

For one-row statements, the SET clause may be more simple, because you don't need to remember the columns order. All values are specified in the form col = expr.

Values can also be specified in the form of a SQL expression or subquery. However, the subquery cannot access the same table that is named in the INTO clause.

If you use the LOW_PRIORITY keyword, execution of the INSERT is delayed until no other clients are reading from the table. If you use the HIGH_PRIORITY keyword, the statement has the same priority as SELECTs. This affects only storage engines that use only table-level locking (MyISAM, MEMORY, MERGE). However, if one of these keywords is specified, concurrent inserts cannot be used. See HIGH_PRIORITY and LOW_PRIORITY clauses for details.

INSERT DELAYED

For more details on the DELAYED option, see INSERT DELAYED.

HIGH PRIORITY and LOW PRIORITY

See HIGH_PRIORITY and LOW_PRIORITY.

Defaults and Duplicate Values

See INSERT - Default & Duplicate Values for details..

INSERT IGNORE

See INSERT IGNORE.

INSERT ON DUPLICATE KEY UPDATE

See INSERT ON DUPLICATE KEY UPDATE.

Examples

Specifying the column names:

INSERT INTO person (first_name, last_name) VALUES ('John', 'Doe');

Inserting more than 1 row at a time:

INSERT INTO tbl_name VALUES (1, "row 1"), (2, "row 2");

Using the SET clause:

INSERT INTO person SET first_name = 'John', last_name = 'Doe';

SELECTing from another table:

INSERT INTO contractor SELECT * FROM person WHERE status = 'c';

See INSERT ON DUPLICATE KEY UPDATE and INSERT IGNORE for further examples.

INSERT ... RETURNING

INSERT ... RETURNING returns a resultset of the inserted rows.

This returns the listed columns for all the rows that are inserted, or alternatively, the specified SELECT expression. Any SQL expressions which can be calculated can be used in the select expression for the RETURNING clause, including virtual columns and aliases, expressions which use various operators such as bitwise, logical and arithmetic operators, string functions, date-time functions, numeric functions, control flow functions, secondary functions and stored functions. Along with this, statements which have subqueries and prepared statements can also be used.

Examples

Simple INSERT statement

INSERT INTO t2 VALUES (1,'Dog'),(2,'Lion'),(3,'Tiger'),(4,'Leopard') 
RETURNING id2,id2+id2,id2&id2,id2||id2;
+-----+---------+---------+----------+
| id2 | id2+id2 | id2&id2 | id2||id2 |
+-----+---------+---------+----------+
|   1 |       2 |       1 |        1 |
|   2 |       4 |       2 |        1 |
|   3 |       6 |       3 |        1 |
|   4 |       8 |       4 |        1 |
+-----+---------+---------+----------+

Using stored functions in RETURNING

DELIMITER |
CREATE FUNCTION f(arg INT) RETURNS INT
    BEGIN
       RETURN (SELECT arg+arg);
    END|

DELIMITER ;

PREPARE stmt FROM "INSERT INTO t1 SET id1=1, animal1='Bear' RETURNING f(id1), UPPER(animal1)";

EXECUTE stmt;
+---------+----------------+
| f(id1)  | UPPER(animal1) |
+---------+----------------+
|       2 | BEAR           |
+---------+----------------+

Subqueries in the RETURNING clause that return more than one row or column cannot be used.

Aggregate functions cannot be used in the RETURNING clause. Since aggregate functions work on a set of values, and if the purpose is to get the row count, ROW_COUNT() with SELECT can be used or it can be used in INSERT...SELECT...RETURNING if the table in the RETURNING clause is not the same as the INSERT table.

See Also

1.1.1.4.2.2 INSERT DELAYED

Syntax

INSERT DELAYED ...

Contents

  1. Syntax
  2. Description
    1. Limitations
  3. See Also

Description

The DELAYED option for the INSERT statement is a MariaDB/MySQL extension to standard SQL that is very useful if you have clients that cannot or need not wait for the INSERT to complete. This is a common situation when you use MariaDB for logging and you also periodically run SELECT and UPDATE statements that take a long time to complete.

When a client uses INSERT DELAYED, it gets an okay from the server at once, and the row is queued to be inserted when the table is not in use by any other thread.

Another major benefit of using INSERT DELAYED is that inserts from many clients are bundled together and written in one block. This is much faster than performing many separate inserts.

Note that INSERT DELAYED is slower than a normal INSERT if the table is not otherwise in use. There is also the additional overhead for the server to handle a separate thread for each table for which there are delayed rows. This means that you should use INSERT DELAYED only when you are really sure that you need it.

The queued rows are held only in memory until they are inserted into the table. This means that if you terminate mysqld forcibly (for example, with kill -9) or if mysqld dies unexpectedly, any queued rows that have not been written to disk are lost.

The number of concurrent INSERT DELAYED threads is limited by the max_delayed_threads server system variables. If it is set to 0, INSERT DELAYED is disabled. The session value can be equal to the global value, or 0 to disable this statement for the current session. If this limit has been reached, the DELAYED clause will be silently ignore for subsequent statements (no error will be produced).

Limitations

There are some limitations on the use of DELAYED:

  • INSERT DELAYED works only with MyISAM, MEMORY, ARCHIVE, and BLACKHOLE tables. If you execute INSERT DELAYED with another storage engine, you will get an error like this: ERROR 1616 (HY000): DELAYED option not supported for table 'tab_name'
  • For MyISAM tables, if there are no free blocks in the middle of the data file, concurrent SELECT and INSERT statements are supported. Under these circumstances, you very seldom need to use INSERT DELAYED with MyISAM.
  • INSERT DELAYED should be used only for INSERT statements that specify value lists. The server ignores DELAYED for INSERT ... SELECT or INSERT ... ON DUPLICATE KEY UPDATE statements.
  • Because the INSERT DELAYED statement returns immediately, before the rows are inserted, you cannot use LAST_INSERT_ID() to get the AUTO_INCREMENT value that the statement might generate.
  • DELAYED rows are not visible to SELECT statements until they actually have been inserted.
  • After INSERT DELAYED, ROW_COUNT() returns the number of the rows you tried to insert, not the number of the successful writes.
  • DELAYED is ignored on slave replication servers, so that INSERT DELAYED is treated as a normal INSERT on slaves. This is because DELAYED could cause the slave to have different data than the master. INSERT DELAYED statements are not safe for replication.
  • Pending INSERT DELAYED statements are lost if a table is write locked and ALTER TABLE is used to modify the table structure.
  • INSERT DELAYED is not supported for views. If you try, you will get an error like this: ERROR 1347 (HY000): 'view_name' is not BASE TABLE
  • INSERT DELAYED is not supported for partitioned tables.
  • INSERT DELAYED is not supported within stored programs.
  • INSERT DELAYED does not work with triggers.
  • INSERT DELAYED does not work if there is a check constraint in place.
  • INSERT DELAYED does not work if skip-new mode is active.

See Also

1.1.1.4.2.3 INSERT SELECT

Syntax

INSERT [LOW_PRIORITY | HIGH_PRIORITY] [IGNORE]
    [INTO] tbl_name [(col_name,...)]
    SELECT ...
    [ ON DUPLICATE KEY UPDATE col_name=expr, ... ]

Contents

  1. Syntax
  2. Description
  3. See Also

Description

With INSERT ... SELECT, you can quickly insert many rows into a table from one or more other tables. For example:

INSERT INTO tbl_temp2 (fld_id)
  SELECT tbl_temp1.fld_order_id
  FROM tbl_temp1 WHERE tbl_temp1.fld_order_id > 100;

tbl_name can also be specified in the form db_name.tbl_name (see Identifier Qualifiers). This allows to copy rows between different databases.

If the new table has a primary key or UNIQUE indexes, you can use IGNORE to handle duplicate key errors during the query. The newer values will not be inserted if an identical value already exists.

REPLACE can be used instead of INSERT to prevent duplicates on UNIQUE indexes by deleting old values. In that case, ON DUPLICATE KEY UPDATE cannot be used.

INSERT ... SELECT works for tables which already exist. To create a table for a given resultset, you can use CREATE TABLE ... SELECT.

See Also

1.1.1.4.2.4 LOAD Data into Tables or Index

Loading data quickly into MariaDB

There are 3 related questions.

1.1.1.4.2.4.1 LOAD DATA INFILE

Syntax

LOAD DATA [LOW_PRIORITY | CONCURRENT] [LOCAL] INFILE 'file_name'
    [REPLACE | IGNORE]
    INTO TABLE tbl_name
    [CHARACTER SET charset_name]
    [{FIELDS | COLUMNS}
        [TERMINATED BY 'string']
        [[OPTIONALLY] ENCLOSED BY 'char']
        [ESCAPED BY 'char']
    ]
    [LINES
        [STARTING BY 'string']
        [TERMINATED BY 'string']
    ]
    [IGNORE number LINES]
    [(col_name_or_user_var,...)]
    [SET col_name = expr,...]

Contents

  1. Syntax
  2. Description
    1. LOAD DATA LOCAL INFILE
    2. REPLACE and IGNORE
    3. Character-sets
    4. Preprocessing Inputs
    5. Priority and Concurrency
    6. Progress Reporting
    7. Using mariadb-import/mysqlimport
    8. Indexing
  3. Examples
  4. See Also

Description

LOAD DATA INFILE is unsafe for statement-based replication.

Reads rows from a text file into the designated table on the database at a very high speed. The file name must be given as a literal string.

Files are written to disk using the SELECT INTO OUTFILE statement. You can then read the files back into a table using the LOAD DATA INFILE statement. The FIELDS and LINES clauses are the same in both statements. These clauses are optional, but if both are specified then the FIELDS clause must precede LINES.

Executing this statement activates INSERT triggers.

One must have the FILE privilege to be able to execute LOAD DATA. This is the ensure the normal users will not attempt to read system files.

Note that MariaDB's systemd unit file restricts access to /home, /root, and /run/user by default. See Configuring access to home directories.

LOAD DATA LOCAL INFILE

When you execute the LOAD DATA INFILE statement, MariaDB Server attempts to read the input file from its own file system. In contrast, when you execute the LOAD DATA LOCAL INFILE statement, the client attempts to read the input file from its file system, and it sends the contents of the input file to the MariaDB Server. This allows you to load files from the client's local file system into the database.

In the event that you don't want to permit this operation (such as for security reasons), you can disable the LOAD DATA LOCAL INFILE statement on either the server or the client.

  • The LOAD DATA LOCAL INFILE statement can be disabled on the server by setting the local_infile system variable to 0.
  • The LOAD DATA LOCAL INFILE statement can be disabled on the client. If you are using MariaDB Connector/C, this can be done by unsetting the CLIENT_LOCAL_FILES capability flag with the mysql_real_connect function or by unsetting the MYSQL_OPT_LOCAL_INFILE option with mysql_optionsv function. If you are using a different client or client library, then see the documentation for your specific client or client library to determine how it handles the LOAD DATA LOCAL INFILE statement.

If the LOAD DATA LOCAL INFILE statement is disabled by either the server or the client and if the user attempts to execute it, then the server will cause the statement to fail with the following error message:

The used command is not allowed with this MariaDB version

Note that it is not entirely accurate to say that the MariaDB version does not support the command. It would be more accurate to say that the MariaDB configuration does not support the command. See MDEV-20500 for more information.

From MariaDB 10.5.2, the error message is more accurate:

The used command is not allowed because the MariaDB server or client 
  has disabled the local infile capability

REPLACE and IGNORE

In cases where you load data from a file into a table that already contains data and has a primary key, you may encounter issues where the statement attempts to insert a row with a primary key that already exists. When this happens, the statement fails with Error 1064, protecting the data already on the table. In cases where you want MariaDB to overwrite duplicates, use the REPLACE keyword.

The REPLACE keyword works like the REPLACE statement. Here, the statement attempts to load the data from the file. If the row does not exist, it adds it to the table. If the row contains an existing Primary Key, it replaces the table data. That is, in the event of a conflict, it assumes the file contains the desired row.

This operation can cause a degradation in load speed by a factor of 20 or more if the part that has already been loaded is larger than the capacity of the InnoDB Buffer Pool. This happens because it causes a lot of turnaround in the buffer pool.

Use the IGNORE keyword when you want to skip any rows that contain a conflicting primary key. Here, the statement attempts to load the data from the file. If the row does not exist, it adds it to the table. If the row contains an existing primary key, it ignores the addition request and moves on to the next. That is, in the event of a conflict, it assumes the table contains the desired row.

Character-sets

When the statement opens the file, it attempts to read the contents using the default character-set, as defined by the character_set_database system variable.

In the cases where the file was written using a character-set other than the default, you can specify the character-set to use with the CHARACTER SET clause in the statement. It ignores character-sets specified by the SET NAMES statement and by the character_set_client system variable. Setting the CHARACTER SET clause to a value of binary indicates "no conversion."

The statement interprets all fields in the file as having the same character-set, regardless of the column data type. To properly interpret file contents, you must ensure that it was written with the correct character-set. If you write a data file with mysqldump -T or with the SELECT INTO OUTFILE statement with the mysql client, be sure to use the --default-character-set option, so that the output is written with the desired character-set.

When using mixed character sets, use the CHARACTER SET clause in both SELECT INTO OUTFILE and LOAD DATA INFILE to ensure that MariaDB correctly interprets the escape sequences.

The character_set_filesystem system variable controls the interpretation of the filename.

It is currently not possible to load data files that use the ucs2 character set.

Preprocessing Inputs

col_name_or_user_var can be a column name, or a user variable. In the case of a variable, the SET statement can be used to preprocess the value before loading into the table.

Priority and Concurrency

In storage engines that perform table-level locking (MyISAM, MEMORY and MERGE), using the LOW_PRIORITY keyword, MariaDB delays insertions until no other clients are reading from the table. Alternatively, when using the MyISAM storage engine, you can use the CONCURRENT keyword to perform concurrent insertion.

The LOW_PRIORITY and CONCURRENT keywords are mutually exclusive. They cannot be used in the same statement.

Progress Reporting

The LOAD DATA INFILE statement supports progress reporting. You may find this useful when dealing with long-running operations. Using another client you can issue a SHOW PROCESSLIST query to check the progress of the data load.

Using mariadb-import/mysqlimport

MariaDB ships with a separate utility for loading data from files: mariadb-import (or mysqlimport before MariaDB 10.5). It operates by sending LOAD DATA INFILE statements to the server.

Using mariadb-import/mysqlimport you can compress the file using the --compress option, to get better performance over slow networks, providing both the client and server support the compressed protocol. Use the --local option to load from the local file system.

Indexing

In cases where the storage engine supports ALTER TABLE... DISABLE KEYS statements (MyISAM and Aria), the LOAD DATA INFILE statement automatically disables indexes during the execution.

Examples

You have a file with this content (note the the separator is ',', not tab, which is the default):

2,2
3,3
4,4
5,5
6,8

CREATE TABLE t1 (a int, b int, c int, d int);
LOAD DATA LOCAL INFILE 
 '/tmp/loaddata7.dat' into table t1 fields terminated by ',' (a,b) set c=a+b;
SELECT * FROM t1;
+------+------+------+
| a    | b    | c    |
+------+------+------+
|    2 |    2 |    4 |
|    3 |    3 |    6 |
|    4 |    4 |    8 |
|    5 |    5 |   10 |
|    6 |    8 |   14 |
+------+------+------+

Another example, given the following data (the separator is a tab):

1       a
2       b

The value of the first column is doubled before loading:

LOAD DATA INFILE 'ld.txt' INTO TABLE ld (@i,v) SET i=@i*2;

SELECT * FROM ld;
+------+------+
| i    | v    |
+------+------+
|    2 | a    |
|    4 | b    |
+------+------+

See Also

1.1.1.4.2.4.2 LOAD INDEX

1.1.1.4.2.4.3 LOAD XML

Syntax

LOAD XML [LOW_PRIORITY | CONCURRENT] [LOCAL] INFILE 'file_name'
    [REPLACE | IGNORE]
    INTO TABLE [db_name.]tbl_name
    [CHARACTER SET charset_name]
    [ROWS IDENTIFIED BY '<tagname>']
    [IGNORE number {LINES | ROWS}]
    [(column_or_user_var,...)]
    [SET col_name = expr,...]

Description

The LOAD XML statement reads data from an XML file into a table. The file_name must be given as a literal string. The tagname in the optional ROWS IDENTIFIED BY clause must also be given as a literal string, and must be surrounded by angle brackets (< and >).

LOAD XML acts as the complement of running the mysql client in XML output mode (that is, starting the client with the --xml option). To write data from a table to an XML file, use a command such as the following one from the system shell:

shell> mysql --xml -e 'SELECT * FROM mytable' > file.xml

To read the file back into a table, use LOAD XML INFILE. By default, the <row> element is considered to be the equivalent of a database table row; this can be changed using the ROWS IDENTIFIED BY clause.

This statement supports three different XML formats:

  • Column names as attributes and column values as attribute values: 
<row column1="value1" column2="value2" .../>
  • Column names as tags and column values as the content of these tags: 
<row>
  <column1>value1</column1>
  <column2>value2</column2>
</row>
  • Column names are the name attributes of <field> tags, and values are the contents of these tags: 
<row>
  <field name='column1'>value1</field>
  <field name='column2'>value2</field>
</row>

This is the format used by other tools, such as mysqldump.

All 3 formats can be used in the same XML file; the import routine automatically detects the format for each row and interprets it correctly. Tags are matched based on the tag or attribute name and the column name.

The following clauses work essentially the same way for LOAD XML as they do for LOAD DATA:

  • LOW_PRIORITY or CONCURRENT
  • LOCAL
  • REPLACE or IGNORE
  • CHARACTER SET
  • (column_or_user_var,...)
  • SET

See LOAD DATA for more information about these clauses.

The IGNORE number LINES or IGNORE number ROWS clause causes the first number rows in the XML file to be skipped. It is analogous to the LOAD DATA statement's IGNORE ... LINES clause.

If the LOW_PRIORITY keyword is used, insertions are delayed until no other clients are reading from the table. The CONCURRENT keyword allowes the use of concurrent inserts. These clauses cannot be specified together.

This statement activates INSERT triggers.

See also

1.1.1.4.2.4.4 LOAD_FILE

Syntax

LOAD_FILE(file_name)

Contents

  1. Syntax
  2. Description
  3. Examples
  4. See Also

Description

Reads the file and returns the file contents as a string. To use this function, the file must be located on the server host, you must specify the full path name to the file, and you must have the FILE privilege. The file must be readable by all and it must be less than the size, in bytes, of the max_allowed_packet system variable. If the secure_file_priv system variable is set to a non-empty directory name, the file to be loaded must be located in that directory.

If the file does not exist or cannot be read because one of the preceding conditions is not satisfied, the function returns NULL.

Since MariaDB 5.1, the character_set_filesystem system variable has controlled interpretation of file names that are given as literal strings.

Statements using the LOAD_FILE() function are not safe for statement based replication. This is because the slave will execute the LOAD_FILE() command itself. If the file doesn't exist on the slave, the function will return NULL.

Examples

UPDATE t SET blob_col=LOAD_FILE('/tmp/picture') WHERE id=1;

See Also

1.1.1.4.2.5 Concurrent Inserts

Contents

  1. Notes
  2. See Also

The MyISAM storage engine supports concurrent inserts. This feature allows SELECT statements to be executed during INSERT operations, reducing contention.

Whether concurrent inserts can be used or not depends on the value of the concurrent_insert server system variable:

  • NEVER (0) disables concurrent inserts.
  • AUTO (1) allows concurrent inserts only when the target table has no free blocks (no data in the middle of the table has been deleted after the last OPTIMIZE TABLE). This is the default.
  • ALWAYS (2) always enables concurrent inserts, in which case new rows are added at the end of a table if the table is being used by another thread.

If the binary log is used, CREATE TABLE ... SELECT and INSERT ... SELECT statements cannot use concurrent inserts. These statements acquire a read lock on the table, so concurrent inserts will need to wait. This way the log can be safely used to restore data.

Concurrent inserts are not used by replicas with the row based replication (see binary log formats).

If an INSERT statement contain the HIGH_PRIORITY clause, concurrent inserts cannot be used. INSERT ... DELAYED is usually unneeded if concurrent inserts are enabled.

LOAD DATA INFILE uses concurrent inserts if the CONCURRENT keyword is specified and concurrent_insert is not NEVER. This makes the statement slower (even if no other sessions access the table) but reduces contention.

LOCK TABLES allows non-conflicting concurrent inserts if a READ LOCAL lock is used. Concurrent inserts are not allowed if the LOCAL keyword is omitted.

Notes

The decision to enable concurrent insert for a table is done when the table is opened. If you change the value of concurrent_insert it will only affect new opened tables. If you want it to work for also for tables in use or cached, you should do FLUSH TABLES after setting the variable.

See Also

1.1.1.4.2.6 HIGH_PRIORITY and LOW_PRIORITY

Contents

  1. See Also

The InnoDB storage engine uses row-level locking to ensure data integrity. However some storage engines (such as MEMORY, MyISAM, Aria and MERGE) lock the whole table to prevent conflicts. These storage engines use two separate queues to remember pending statements; one is for SELECTs and the other one is for write statements (INSERT, DELETE, UPDATE). By default, the latter has a higher priority.

To give write operations a lower priority, the low_priority_updates server system variable can be set to ON. The option is available on both the global and session levels, and it can be set at startup or via the SET statement.

When too many table locks have been set by write statements, some pending SELECTs are executed. The maximum number of write locks that can be acquired before this happens is determined by the max_write_lock_count server system variable, which is dynamic.

If write statements have a higher priority (default), the priority of individual write statements (INSERT, REPLACE, UPDATE, DELETE) can be changed via the LOW_PRIORITY attribute, and the priority of a SELECT statement can be raised via the HIGH_PRIORITY attribute. Also, LOCK TABLES supports a LOW_PRIORITY attribute for WRITE locks.

If read statements have a higher priority, the priority of an INSERT can be changed via the HIGH_PRIORITY attribute. However, the priority of other write statements cannot be raised individually.

The use of LOW_PRIORITY or HIGH_PRIORITY for an INSERT prevents Concurrent Inserts from being used.

See Also

1.1.1.4.2.7 IGNORE

1.1.1.4.2.8 INSERT - Default & Duplicate Values

Contents

  1. Default Values
  2. Duplicate Values
  3. See Also

Default Values

If the SQL_MODE contains STRICT_TRANS_TABLES and you are inserting into a transactional table (like InnoDB), or if the SQL_MODE contains STRICT_ALL_TABLES, all NOT NULL columns which does not have a DEFAULT value (and is not AUTO_INCREMENT) must be explicitly referenced in INSERT statements. If not, an error like this is produced:

ERROR 1364 (HY000): Field 'col' doesn't have a default value

In all other cases, if a NOT NULL column without a DEFAULT value is not referenced, an empty value will be inserted (for example, 0 for INTEGER columns and '' for CHAR columns). See NULL Values in MariaDB:Inserting for examples.

If a NOT NULL column having a DEFAULT value is not referenced, NULL will be inserted.

If a NULL column having a DEFAULT value is not referenced, its default value will be inserted. It is also possible to explicitly assign the default value using the DEFAULT keyword or the DEFAULT() function.

If the DEFAULT keyword is used but the column does not have a DEFAULT value, an error like this is produced:

ERROR 1364 (HY000): Field 'col' doesn't have a default value

Duplicate Values

By default, if you try to insert a duplicate row and there is a UNIQUE index, INSERT stops and an error like this is produced:

ERROR 1062 (23000): Duplicate entry 'dup_value' for key 'col'

To handle duplicates you can use the IGNORE clause, INSERT ON DUPLICATE KEY UPDATE or the REPLACE statement. Note that the IGNORE and DELAYED options are ignored when you use ON DUPLICATE KEY UPDATE.

See Also

1.1.1.4.2.9 INSERT IGNORE

Contents

  1. Ignoring Errors
  2. Examples
  3. See Also

Ignoring Errors

Normally INSERT stops and rolls back when it encounters an error.

By using the IGNORE keyword all errors are converted to warnings, which will not stop inserts of additional rows.

The IGNORE and DELAYED options are ignored when you use ON DUPLICATE KEY UPDATE.

Prior to MySQL and MariaDB 5.5.28, no warnings were issued for duplicate key errors when using IGNORE. You can get the old behavior if you set OLD_MODE to NO_DUP_KEY_WARNINGS_WITH_IGNORE.

Examples

CREATE TABLE t1 (x INT UNIQUE);

INSERT INTO t1 VALUES(1),(2);

INSERT INTO t1 VALUES(2),(3);
ERROR 1062 (23000): Duplicate entry '2' for key 'x'
SELECT * FROM t1;
+------+
| x    |
+------+
|    1 |
|    2 |
+------+
2 rows in set (0.00 sec)

INSERT IGNORE INTO t1 VALUES(2),(3);
Query OK, 1 row affected, 1 warning (0.04 sec)

SHOW WARNINGS;
+---------+------+---------------------------------+
| Level   | Code | Message                         |
+---------+------+---------------------------------+
| Warning | 1062 | Duplicate entry '2' for key 'x' |
+---------+------+---------------------------------+

SELECT * FROM t1;
+------+
| x    |
+------+
|    1 |
|    2 |
|    3 |
+------+

See INSERT ON DUPLICATE KEY UPDATE for further examples using that syntax.

See Also

1.1.1.4.2.10 INSERT ON DUPLICATE KEY UPDATE

Syntax

INSERT [LOW_PRIORITY | DELAYED | HIGH_PRIORITY] [IGNORE]
  [INTO] tbl_name [PARTITION (partition_list)] [(col,...)]
  {VALUES | VALUE} ({expr | DEFAULT},...),(...),...
  [ ON DUPLICATE KEY UPDATE
    col=expr
      [, col=expr] ... ]

Or:

INSERT [LOW_PRIORITY | DELAYED | HIGH_PRIORITY] [IGNORE]
    [INTO] tbl_name [PARTITION (partition_list)]
    SET col={expr | DEFAULT}, ...
    [ ON DUPLICATE KEY UPDATE
      col=expr
        [, col=expr] ... ]

Or:

INSERT [LOW_PRIORITY | HIGH_PRIORITY] [IGNORE]
    [INTO] tbl_name [PARTITION (partition_list)] [(col,...)]
    SELECT ...
    [ ON DUPLICATE KEY UPDATE
      col=expr
        [, col=expr] ... ]

Contents

  1. Syntax
  2. Description
  3. Examples
  4. See Also

Description

INSERT ... ON DUPLICATE KEY UPDATE is a MariaDB/MySQL extension to the INSERT statement that, if it finds a duplicate unique or primary key, will instead perform an UPDATE.

The row/s affected value is reported as 1 if a row is inserted, and 2 if a row is updated, unless the API's CLIENT_FOUND_ROWS flag is set.

If more than one unique index is matched, only the first is updated. It is not recommended to use this statement on tables with more than one unique index.

If the table has an AUTO_INCREMENT primary key and the statement inserts or updates a row, the LAST_INSERT_ID() function returns its AUTO_INCREMENT value.

The VALUES() function can only be used in a ON DUPLICATE KEY UPDATE clause and has no meaning in any other context. It returns the column values from the INSERT portion of the statement. This function is particularly useful for multi-rows inserts.

The IGNORE and DELAYED options are ignored when you use ON DUPLICATE KEY UPDATE.

See Partition Pruning and Selection for details on the PARTITION clause.

This statement activates INSERT and UPDATE triggers. See Trigger Overview for details.

See also a similar statement, REPLACE.

Examples

CREATE TABLE ins_duplicate (id INT PRIMARY KEY, animal VARCHAR(30));
INSERT INTO ins_duplicate VALUES (1,'Aardvark'), (2,'Cheetah'), (3,'Zebra');

If there is no existing key, the statement runs as a regular INSERT:

INSERT INTO ins_duplicate VALUES (4,'Gorilla') 
  ON DUPLICATE KEY UPDATE animal='Gorilla';
Query OK, 1 row affected (0.07 sec)

SELECT * FROM ins_duplicate;
+----+----------+
| id | animal   |
+----+----------+
|  1 | Aardvark |
|  2 | Cheetah  |
|  3 | Zebra    |
|  4 | Gorilla  |
+----+----------+

A regular INSERT with a primary key value of 1 will fail, due to the existing key:

INSERT INTO ins_duplicate VALUES (1,'Antelope');
ERROR 1062 (23000): Duplicate entry '1' for key 'PRIMARY'

However, we can use an INSERT ON DUPLICATE KEY UPDATE instead:

INSERT INTO ins_duplicate VALUES (1,'Antelope') 
  ON DUPLICATE KEY UPDATE animal='Antelope';
Query OK, 2 rows affected (0.09 sec)

Note that there are two rows reported as affected, but this refers only to the UPDATE.

SELECT * FROM ins_duplicate;
+----+----------+
| id | animal   |
+----+----------+
|  1 | Antelope |
|  2 | Cheetah  |
|  3 | Zebra    |
|  4 | Gorilla  |
+----+----------+

Adding a second unique column:

ALTER TABLE ins_duplicate ADD id2 INT;
UPDATE ins_duplicate SET id2=id+10;
ALTER TABLE ins_duplicate ADD UNIQUE KEY(id2);

Where two rows match the unique keys match, only the first is updated. This can be unsafe and is not recommended unless you are certain what you are doing.

INSERT INTO ins_duplicate VALUES (2,'Lion',13) 
  ON DUPLICATE KEY UPDATE animal='Lion';
Query OK, 2 rows affected (0.004 sec)

SELECT * FROM ins_duplicate;
+----+----------+------+
| id | animal   | id2  |
+----+----------+------+
|  1 | Antelope |   11 |
|  2 | Lion     |   12 |
|  3 | Zebra    |   13 |
|  4 | Gorilla  |   14 |
+----+----------+------+

Although the third row with an id of 3 has an id2 of 13, which also matched, it was not updated.

Changing id to an auto_increment field. If a new row is added, the auto_increment is moved forward. If the row is updated, it remains the same.

ALTER TABLE `ins_duplicate` CHANGE `id` `id` INT( 11 ) NOT NULL AUTO_INCREMENT;
ALTER TABLE ins_duplicate DROP id2;
SELECT Auto_increment FROM INFORMATION_SCHEMA.TABLES 
  WHERE TABLE_NAME='ins_duplicate';
+----------------+
| Auto_increment |
+----------------+
|              5 |
+----------------+

INSERT INTO ins_duplicate VALUES (2,'Leopard') 
  ON DUPLICATE KEY UPDATE animal='Leopard';
Query OK, 2 rows affected (0.00 sec)

SELECT Auto_increment FROM INFORMATION_SCHEMA.TABLES 
  WHERE TABLE_NAME='ins_duplicate';
+----------------+
| Auto_increment |
+----------------+
|              5 |
+----------------+

INSERT INTO ins_duplicate VALUES (5,'Wild Dog') 
  ON DUPLICATE KEY UPDATE animal='Wild Dog';
Query OK, 1 row affected (0.09 sec)

SELECT * FROM ins_duplicate;
+----+----------+
| id | animal   |
+----+----------+
|  1 | Antelope |
|  2 | Leopard  |
|  3 | Zebra    |
|  4 | Gorilla  |
|  5 | Wild Dog |
+----+----------+

SELECT Auto_increment FROM INFORMATION_SCHEMA.TABLES 
  WHERE TABLE_NAME='ins_duplicate';
+----------------+
| Auto_increment |
+----------------+
|              6 |
+----------------+

Refering to column values from the INSERT portion of the statement: 

INSERT INTO table (a,b,c) VALUES (1,2,3),(4,5,6)
    ON DUPLICATE KEY UPDATE c=VALUES(a)+VALUES(b);

See the VALUES() function for more.

See Also

1.1.1.4.2.11 INSERT...RETURNING

MariaDB starting with 10.5.0

INSERT ... RETURNING was added in MariaDB 10.5.0, and returns a resultset of the inserted rows.

Syntax

INSERT [LOW_PRIORITY | DELAYED | HIGH_PRIORITY] [IGNORE]
 [INTO] tbl_name [PARTITION (partition_list)] [(col,...)]
 {VALUES | VALUE} ({expr | DEFAULT},...),(...),...
 [ ON DUPLICATE KEY UPDATE
   col=expr
     [, col=expr] ... ] [RETURNING select_expr 
      [, select_expr ...]]

Or:

INSERT [LOW_PRIORITY | DELAYED | HIGH_PRIORITY] [IGNORE]
    [INTO] tbl_name [PARTITION (partition_list)]
    SET col={expr | DEFAULT}, ...
    [ ON DUPLICATE KEY UPDATE
      col=expr
        [, col=expr] ... ] [RETURNING select_expr 
      [, select_expr ...]]

Or:

INSERT [LOW_PRIORITY | HIGH_PRIORITY] [IGNORE]
    [INTO] tbl_name [PARTITION (partition_list)] [(col,...)]
    SELECT ...
    [ ON DUPLICATE KEY UPDATE
      col=expr
        [, col=expr] ... ] [RETURNING select_expr 
      [, select_expr ...]]

Contents

  1. Syntax
  2. Description
  3. Examples
  4. See Also

Description

INSERT ... RETURNING returns a resultset of the inserted rows.

This returns the listed columns for all the rows that are inserted, or alternatively, the specified SELECT expression. Any SQL expressions which can be calculated can be used in the select expression for the RETURNING clause, including virtual columns and aliases, expressions which use various operators such as bitwise, logical and arithmetic operators, string functions, date-time functions, numeric functions, control flow functions, secondary functions and stored functions. Along with this, statements which have subqueries and prepared statements can also be used.

Examples

Simple INSERT statements:

CREATE OR REPLACE TABLE t2 (id INT, animal VARCHAR(20), t TIMESTAMP);

INSERT INTO t2 (id) VALUES (2),(3) RETURNING id,t;
+------+---------------------+
| id   | t                   |
+------+---------------------+
|    2 | 2021-04-28 00:59:32 |
|    3 | 2021-04-28 00:59:32 |
+------+---------------------+

INSERT INTO t2(id,animal) VALUES (1,'Dog'),(2,'Lion'),(3,'Tiger'),(4,'Leopard')  
  RETURNING id,id+id,id&id,id||id;
+------+-------+-------+--------+
| id   | id+id | id&id | id||id |
+------+-------+-------+--------+
|    1 |     2 |     1 |      1 |
|    2 |     4 |     2 |      1 |
|    3 |     6 |     3 |      1 |
|    4 |     8 |     4 |      1 |
+------+-------+-------+--------+

Using stored functions in RETURNING

DELIMITER |
CREATE FUNCTION f(arg INT) RETURNS INT
    BEGIN
       RETURN (SELECT arg+arg);
    END|

DELIMITER ;

PREPARE stmt FROM "INSERT INTO t1 SET id1=1, animal1='Bear' RETURNING f(id1), UPPER(animal1)";

EXECUTE stmt;
+---------+----------------+
| f(id1)  | UPPER(animal1) |
+---------+----------------+
|       2 | BEAR           |
+---------+----------------+

Subqueries in the RETURNING clause that return more than one row or column cannot be used.

Aggregate functions cannot be used in the RETURNING clause. Since aggregate functions work on a set of values, and if the purpose is to get the row count, ROW_COUNT() with SELECT can be used or it can be used in INSERT...SELECT...RETURNING if the table in the RETURNING clause is not the same as the INSERT table.

See Also

1.1.1.4.3 Changing & Deleting Data

1.1.1.4.3.1 DELETE

1.1.1.4.3.2 HIGH_PRIORITY and LOW_PRIORITY

1.1.1.4.3.3 IGNORE

1.1.1.4.3.4 REPLACE

1.1.1.4.3.5 REPLACE...RETURNING

MariaDB starting with 10.5.0

REPLACE ... RETURNING was added in MariaDB 10.5.0, and returns a resultset of the replaced rows.

Syntax

REPLACE [LOW_PRIORITY | DELAYED]
 [INTO] tbl_name [PARTITION (partition_list)] [(col,...)]
 {VALUES | VALUE} ({expr | DEFAULT},...),(...),...
[RETURNING select_expr 
      [, select_expr ...]]

Or:

REPLACE [LOW_PRIORITY | DELAYED]
    [INTO] tbl_name [PARTITION (partition_list)]
    SET col={expr | DEFAULT}, ...
[RETURNING select_expr 
      [, select_expr ...]]

Or:

REPLACE [LOW_PRIORITY | DELAYED]
    [INTO] tbl_name [PARTITION (partition_list)] [(col,...)]
    SELECT ...
[RETURNING select_expr 
      [, select_expr ...]]

Contents

  1. Syntax
  2. Description
  3. Examples
  4. See Also

Description

REPLACE ... RETURNING returns a resultset of the replaced rows.

This returns the listed columns for all the rows that are replaced, or alternatively, the specified SELECT expression. Any SQL expressions which can be calculated can be used in the select expression for the RETURNING clause, including virtual columns and aliases, expressions which use various operators such as bitwise, logical and arithmetic operators, string functions, date-time functions, numeric functions, control flow functions, secondary functions and stored functions. Along with this, statements which have subqueries and prepared statements can also be used.

Examples

Simple REPLACE statement

REPLACE INTO t2 VALUES (1,'Leopard'),(2,'Dog') RETURNING id2, id2+id2 
as Total ,id2|id2, id2&&id2;
+-----+-------+---------+----------+
| id2 | Total | id2|id2 | id2&&id2 |
+-----+-------+---------+----------+
|   1 |     2 |       1 |        1 |
|   2 |     4 |       2 |        1 |
+-----+-------+---------+----------+

Using stored functions in RETURNING

DELIMITER |
CREATE FUNCTION f(arg INT) RETURNS INT
    BEGIN
      RETURN (SELECT arg+arg);
    END|

DELIMITER ;
PREPARE stmt FROM "REPLACE INTO t2 SET id2=3, animal2='Fox' RETURNING f2(id2),
UPPER(animal2)";

EXECUTE stmt;
+---------+----------------+
| f2(id2) | UPPER(animal2) |
+---------+----------------+
|       6 | FOX            |
+---------+----------------+

Subqueries in the statement

REPLACE INTO t1 SELECT * FROM t2 RETURNING (SELECT id2 FROM t2 WHERE 
id2 IN (SELECT id2 FROM t2 WHERE id2=1)) AS new_id;
+--------+
| new_id |
+--------+
|      1 |
|      1 |
|      1 |
|      1 |
+--------+

Subqueries in the RETURNING clause that return more than one row or column cannot be used..

Aggregate functions cannot be used in the RETURNING clause. Since aggregate functions work on a set of values and if the purpose is to get the row count, ROW_COUNT() with SELECT can be used, or it can be used in REPLACE...SELECT...RETURNING if the table in the RETURNING clause is not the same as the REPLACE table.

See Also

1.1.1.4.3.6 TRUNCATE TABLE

1.1.1.4.3.7 UPDATE

1.1.1.5 Prepared Statements

In addition to using prepared statements from the libmysqld, you can also do prepared statements from any client by using the text based prepared statement interface.

You first prepare the statement with PREPARE, execute with EXECUTE, and release it with DEALLOCATE.

There are 1 related questions.

1.1.1.5.1 PREPARE Statement

Syntax

PREPARE stmt_name FROM preparable_stmt

Contents

  1. Syntax
  2. Description
    1. Oracle Mode
  3. Permitted Statements
  4. Example
  5. See Also

Description

The PREPARE statement prepares a statement and assigns it a name, stmt_name, by which to refer to the statement later. Statement names are not case sensitive. preparable_stmt is either a string literal or a user variable (not a local variable, an SQL expression or a subquery) that contains the text of the statement. The text must represent a single SQL statement, not multiple statements. Within the statement, "?" characters can be used as parameter markers to indicate where data values are to be bound to the query later when you execute it. The "?" characters should not be enclosed within quotes, even if you intend to bind them to string values. Parameter markers can be used only where expressions should appear, not for SQL keywords, identifiers, and so forth.

The scope of a prepared statement is the session within which it is created. Other sessions cannot see it.

If a prepared statement with the given name already exists, it is deallocated implicitly before the new statement is prepared. This means that if the new statement contains an error and cannot be prepared, an error is returned and no statement with the given name exists.

Prepared statements can be PREPAREd and EXECUTEd in a stored procedure, but not in a stored function or trigger. Also, even if the statement is PREPAREd in a procedure, it will not be deallocated when the procedure execution ends.

A prepared statement can access user-defined variables, but not local variables or procedure's parameters.

If the prepared statement contains a syntax error, PREPARE will fail. As a side effect, stored procedures can use it to check if a statement is valid. For example:

CREATE PROCEDURE `test_stmt`(IN sql_text TEXT)
BEGIN
        DECLARE EXIT HANDLER FOR SQLEXCEPTION
        BEGIN
                SELECT CONCAT(sql_text, ' is not valid');
        END;
        SET @SQL := sql_text;
        PREPARE stmt FROM @SQL;
        DEALLOCATE PREPARE stmt;
END;

The FOUND_ROWS() and ROW_COUNT() functions, if called immediatly after EXECUTE, return the number of rows read or affected by the prepared statements; however, if they are called after DEALLOCATE PREPARE, they provide information about this statement. If the prepared statement produces errors or warnings, GET DIAGNOSTICS return information about them. DEALLOCATE PREPARE shouldn't clear the diagnostics area, unless it produces an error.

A prepared statement is executed with EXECUTE and released with DEALLOCATE PREPARE.

The max_prepared_stmt_count server system variable determines the number of allowed prepared statements that can be prepared on the server. If it is set to 0, prepared statements are not allowed. If the limit is reached, an error similar to the following will be produced:

ERROR 1461 (42000): Can't create more than max_prepared_stmt_count statements 
  (current value: 0)

Oracle Mode

MariaDB starting with 10.3

In Oracle mode from MariaDB 10.3, PREPARE stmt FROM 'SELECT :1, :2' is used, instead of ?.

Permitted Statements

Not all statements can be prepared. Only the following SQL commands are permitted:

Synonyms are not listed here, but can be used. For example, DESC can be used instead of DESCRIBE.

MariaDB starting with 10.1.1

Compound statements can be prepared too.

Note that if a statement can be run in a stored routine, it will work even if it is called by a prepared statement. For example, SIGNAL can't be directly prepared. However, it is allowed in stored routines. If the x() procedure contains SIGNAL, you can still prepare and execute the 'CALL x();' prepared statement.

MariaDB starting with 10.2.3

PREPARE now supports most kinds of expressions as well, for example:

PREPARE stmt FROM CONCAT('SELECT * FROM ', table_name);
MariaDB starting with 10.6.2

All statements can be prepared, except PREPARE, EXECUTE, and DEALLOCATE / DROP PREPARE.

When PREPARE is used with a statement which is not supported, the following error is produced:

ERROR 1295 (HY000): This command is not supported in the prepared statement protocol yet

Example

create table t1 (a int,b char(10));
insert into t1 values (1,"one"),(2, "two"),(3,"three");
prepare test from "select * from t1 where a=?";
set @param=2;
execute test using @param;
+------+------+
| a    | b    |
+------+------+
|    2 | two  |
+------+------+
set @param=3;
execute test using @param;
+------+-------+
| a    | b     |
+------+-------+
|    3 | three |
+------+-------+
deallocate prepare test;

Since identifiers are not permitted as prepared statements parameters, sometimes it is necessary to dynamically compose an SQL statement. This technique is called dynamic SQL). The following example shows how to use dynamic SQL:

CREATE PROCEDURE test.stmt_test(IN tab_name VARCHAR(64))
BEGIN
	SET @sql = CONCAT('SELECT COUNT(*) FROM ', tab_name);
	PREPARE stmt FROM @sql;
	EXECUTE stmt;
	DEALLOCATE PREPARE stmt;
END;

CALL test.stmt_test('mysql.user');
+----------+
| COUNT(*) |
+----------+
|        4 |
+----------+

Use of variables in prepared statements:

PREPARE stmt FROM 'SELECT @x;';

SET @x = 1;

EXECUTE stmt;
+------+
| @x   |
+------+
|    1 |
+------+

SET @x = 0;

EXECUTE stmt;
+------+
| @x   |
+------+
|    0 |
+------+

DEALLOCATE PREPARE stmt;

See Also

1.1.1.5.2 Out Parameters in PREPARE

MariaDB 10.1.1

Out parameters in PREPARE were only available in MariaDB 10.1.1

One can use question mark placeholders for out-parameters in the PREPARE statement. Only SELECT … INTO can be used this way:

prepare test from "select id into ? from t1 where val=?";
execute test using @out, @in;

This is particularly convenient when used with compound statements:

PREPARE stmt FROM "BEGIN NOT ATOMIC
  DECLARE v_res INT;
  SELECT COUNT(*) INTO v_res FROM t1;
  SELECT 'Hello World', v_res INTO ?,?;
END"|

1.1.1.5.3 EXECUTE STATEMENT

1.1.1.5.4 DEALLOCATE / DROP PREPARE

Syntax

{DEALLOCATE | DROP} PREPARE stmt_name

Description

To deallocate a prepared statement produced with PREPARE, use a DEALLOCATE PREPARE statement that refers to the prepared statement name.

A prepared statement is implicitly deallocated when a new PREPARE command is issued. In that case, there is no need to use DEALLOCATE.

Attempting to execute a prepared statement after deallocating it results in an error, as if it was not prepared at all:

ERROR 1243 (HY000): Unknown prepared statement handler (stmt_name) given to EXECUTE

If the specified statement has not been PREPAREd, an error similar to the following will be produced:

ERROR 1243 (HY000): Unknown prepared statement handler (stmt_name) given to DEALLOCATE PREPARE

Example

See example in PREPARE.

See Also

1.1.1.5.5 EXECUTE IMMEDIATE

MariaDB starting with 10.2.3

EXECUTE IMMEDIATE was introduced in MariaDB 10.2.3.

Syntax

EXECUTE IMMEDIATE statement

Description

EXECUTE IMMEDIATE executes a dynamic SQL statement created on the fly, which can reduce performance overhead.

For example:

EXECUTE IMMEDIATE 'SELECT 1'

which is shorthand for:

prepare stmt from "select 1";
execute stmt;
deallocate prepare stmt;

EXECUTE IMMEDIATE supports complex expressions as prepare source and parameters:

EXECUTE IMMEDIATE CONCAT('SELECT COUNT(*) FROM ', 't1', ' WHERE a=?') USING 5+5;

Limitations: subselects and stored function calls are not supported as a prepare source.

The following examples return an error:

CREATE OR REPLACE FUNCTION f1() RETURNS VARCHAR(64) RETURN 'SELECT * FROM t1';
EXECUTE IMMEDIATE f1();
ERROR 1970 (42000): EXECUTE IMMEDIATE does not support subqueries or stored functions

EXECUTE IMMEDIATE (SELECT 'SELECT * FROM t1');
ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that 
  corresponds to your MariaDB server version for the right syntax to use near 
  'SELECT 'SELECT * FROM t1')' at line 1

CREATE OR REPLACE FUNCTION f1() RETURNS INT RETURN 10;
EXECUTE IMMEDIATE 'SELECT * FROM t1 WHERE a=?' USING f1();
ERROR 1970 (42000): EXECUTE..USING does not support subqueries or stored functions

EXECUTE IMMEDIATE 'SELECT * FROM t1 WHERE a=?' USING (SELECT 10);
ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that 
  corresponds to your MariaDB server version for the right syntax to use near 
  'SELECT 10)' at line 1

One can use a user or an SP variable as a workaround:

CREATE OR REPLACE FUNCTION f1() RETURNS VARCHAR(64) RETURN 'SELECT * FROM t1';
SET @stmt=f1();
EXECUTE IMMEDIATE @stmt;

SET @stmt=(SELECT 'SELECT 1');
EXECUTE IMMEDIATE @stmt;

CREATE OR REPLACE FUNCTION f1() RETURNS INT RETURN 10;
SET @param=f1();
EXECUTE IMMEDIATE 'SELECT * FROM t1 WHERE a=?' USING @param;

SET @param=(SELECT 10);
EXECUTE IMMEDIATE 'SELECT * FROM t1 WHERE a=?' USING @param;

EXECUTE IMMEDIATE supports user variables and SP variables as OUT parameters

DELIMITER $$
CREATE OR REPLACE PROCEDURE p1(OUT a INT)
BEGIN
  SET a:= 10;
END;
$$
DELIMITER ;
SET @a=2;
EXECUTE IMMEDIATE 'CALL p1(?)' USING @a;
SELECT @a;
+------+
| @a   |
+------+
|   10 |
+------+

Similar to PREPARE, EXECUTE IMMEDIATE is allowed in stored procedures but is not allowed in stored functions.

This example uses EXECUTE IMMEDIATE inside a stored procedure:

DELIMITER $$
CREATE OR REPLACE PROCEDURE p1()
BEGIN
  EXECUTE IMMEDIATE 'SELECT 1';
END;
$$
DELIMITER ;
CALL p1;
+---+
| 1 |
+---+
| 1 |
+---+

This script returns an error:

DELIMITER $$
CREATE FUNCTION f1() RETURNS INT
BEGIN
  EXECUTE IMMEDIATE 'DO 1';
  RETURN 1;
END;
$$
ERROR 1336 (0A000): Dynamic SQL is not allowed in stored function or trigger

EXECUTE IMMEDIATE can use DEFAULT and IGNORE indicators as bind parameters:

CREATE OR REPLACE TABLE t1 (a INT DEFAULT 10);
EXECUTE IMMEDIATE 'INSERT INTO t1 VALUES (?)' USING DEFAULT;
SELECT * FROM t1;
+------+
| a    |
+------+
|   10 |
+------+

EXECUTE IMMEDIATE increments the Com_execute_immediate status variable, as well as the Com_stmt_prepare, Com_stmt_execute and Com_stmt_close status variables.

Note, EXECUTE IMMEDIATE does not increment the Com_execute_sql status variable. Com_execute_sql is used only for PREPARE..EXECUTE.

This session screenshot demonstrates how EXECUTE IMMEDIATE affects status variables:

SELECT * FROM INFORMATION_SCHEMA.SESSION_STATUS WHERE VARIABLE_NAME RLIKE 
  ('COM_(EXECUTE|STMT_PREPARE|STMT_EXECUTE|STMT_CLOSE)');

+-----------------------+----------------+
| VARIABLE_NAME         | VARIABLE_VALUE |
+-----------------------+----------------+
| COM_EXECUTE_IMMEDIATE | 0              |
| COM_EXECUTE_SQL       | 0              |
| COM_STMT_CLOSE        | 0              |
| COM_STMT_EXECUTE      | 0              |
| COM_STMT_PREPARE      | 0              |
+-----------------------+----------------+

EXECUTE IMMEDIATE 'SELECT 1';
+---+
| 1 |
+---+
| 1 |
+---+

SELECT * FROM INFORMATION_SCHEMA.SESSION_STATUS WHERE VARIABLE_NAME RLIKE 
  ('COM_(EXECUTE|STMT_PREPARE|STMT_EXECUTE|STMT_CLOSE)');
+-----------------------+----------------+
| VARIABLE_NAME         | VARIABLE_VALUE |
+-----------------------+----------------+
| COM_EXECUTE_IMMEDIATE | 1              |
| COM_EXECUTE_SQL       | 0              |
| COM_STMT_CLOSE        | 1              |
| COM_STMT_EXECUTE      | 1              |
| COM_STMT_PREPARE      | 1              |
+-----------------------+----------------+

1.1.1.6 Programmatic & Compound Statements

Compound statements in MariaDB can be used both inside and outside of stored programs.

1.1.1.6.1 Using Compound Statements Outside of Stored Programs

MariaDB starting with 10.1.1

Starting from MariaDB 10.1.1 compound statements can also be used outside of stored programs.

delimiter |
IF @have_innodb THEN
  CREATE TABLE IF NOT EXISTS innodb_index_stats (
    database_name    VARCHAR(64) NOT NULL,
    table_name       VARCHAR(64) NOT NULL,
    index_name       VARCHAR(64) NOT NULL,
    last_update      TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
    stat_name        VARCHAR(64) NOT NULL,
    stat_value       BIGINT UNSIGNED NOT NULL,
    sample_size      BIGINT UNSIGNED,
    stat_description VARCHAR(1024) NOT NULL,
    PRIMARY KEY (database_name, table_name, index_name, stat_name)
  ) ENGINE=INNODB DEFAULT CHARSET=utf8 COLLATE=utf8_bin STATS_PERSISTENT=0;
END IF|
Query OK, 0 rows affected, 2 warnings (0.00 sec)

Note, that using compound statements this way is subject to following limitations:

  • Only BEGIN, IF, CASE, LOOP, WHILE, REPEAT statements may start a compound statement outside of stored programs.
  • BEGIN must use the BEGIN NOT ATOMIC syntax (otherwise it'll be confused with BEGIN that starts a transaction).
  • A compound statement might not start with a label.
  • A compound statement is parsed completely—note "2 warnings" in the above example, even if the condition was false (InnoDB was, indeed, disabled), and the CREATE TABLE statement was not executed, it was still parsed and the parser produced "Unknown storage engine" warning.

Inside a compound block first three limitations do not apply, one can use anything that can be used inside a stored program — including labels, condition handlers, variables, and so on:

BEGIN NOT ATOMIC
    DECLARE foo CONDITION FOR 1146;
    DECLARE x INT DEFAULT 0;
    DECLARE CONTINUE HANDLER FOR SET x=1;
    INSERT INTO test.t1 VALUES ("hndlr1", val, 2);
    END|

Example how to use IF:

IF (1>0) THEN BEGIN NOT ATOMIC SELECT 1; END ; END IF;;

Example of how to use WHILE loop:

DELIMITER |
BEGIN NOT ATOMIC
    DECLARE x INT DEFAULT 0;
    WHILE x <= 10 DO
        SET x = x + 1;
        SELECT x;
    END WHILE;
END|
DELIMITER ;

1.1.1.6.2 BEGIN END

Syntax

[begin_label:] BEGIN [NOT ATOMIC]
    [statement_list]
END [end_label]

Contents

  1. Syntax
  2. Description
  3. See Also

NOT ATOMIC is required when used outside of a stored procedure. Inside stored procedures or within an anonymous block, BEGIN alone starts a new anonymous block.

Description

BEGIN ... END syntax is used for writing compound statements. A compound statement can contain multiple statements, enclosed by the BEGIN and END keywords. statement_list represents a list of one or more statements, each terminated by a semicolon (i.e., ;) statement delimiter. statement_list is optional, which means that the empty compound statement (BEGIN END) is legal.

Note that END will perform a commit. If you are running in autocommit mode, every statement will be committed separately. If you are not running in autocommit mode, you must execute a COMMIT or ROLLBACK after END to get the database up to date.

Use of multiple statements requires that a client is able to send statement strings containing the ; statement delimiter. This is handled in the mysql command-line client with the DELIMITER command. Changing the ; end-of-statement delimiter (for example, to //) allows ; to be used in a program body.

A compound statement within a stored program can be labeled. end_label cannot be given unless begin_label also is present. If both are present, they must be the same.

BEGIN ... END constructs can be nested. Each block can define its own variables, a CONDITION, a HANDLER and a CURSOR, which don't exist in the outer blocks. The most local declarations override the outer objects which use the same name (see example below).

The declarations order is the following:

Note that DECLARE HANDLER contains another BEGIN ... END construct.

Here is an example of a very simple, anonymous block:

BEGIN NOT ATOMIC
SET @a=1;
CREATE TABLE test.t1(a INT);
END|

Below is an example of nested blocks in a stored procedure:

CREATE PROCEDURE t( )
BEGIN
   DECLARE x TINYINT UNSIGNED DEFAULT 1;
   BEGIN
      DECLARE x CHAR(2) DEFAULT '02';
       DECLARE y TINYINT UNSIGNED DEFAULT 10;
       SELECT x, y;
   END;
   SELECT x;
END;

In this example, a TINYINT variable, x is declared in the outter block. But in the inner block x is re-declared as a CHAR and an y variable is declared. The inner SELECT shows the "new" value of x, and the value of y. But when x is selected in the outer block, the "old" value is returned. The final SELECT doesn't try to read y, because it doesn't exist in that context.

See Also

1.1.1.6.3 CASE Statement

Syntax

CASE case_value
    WHEN when_value THEN statement_list
    [WHEN when_value THEN statement_list] ...
    [ELSE statement_list]
END CASE

Or:

CASE
    WHEN search_condition THEN statement_list
    [WHEN search_condition THEN statement_list] ...
    [ELSE statement_list] 
END CASE

Description

The text on this page describes the CASE statement for stored programs. See the CASE OPERATOR for details on the CASE operator outside of stored programs.

The CASE statement for stored programs implements a complex conditional construct. If a search_condition evaluates to true, the corresponding SQL statement list is executed. If no search condition matches, the statement list in the ELSE clause is executed. Each statement_list consists of one or more statements.

The CASE statement cannot have an ELSE NULL clause, and it is terminated with END CASE instead of END. implements a complex conditional construct. If a search_condition evaluates to true, the corresponding SQL statement list is executed. If no search condition matches, the statement list in the ELSE clause is executed. Each statement_list consists of one or more statements.

If no when_value or search_condition matches the value tested and the CASE statement contains no ELSE clause, a Case not found for CASE statement error results.

Each statement_list consists of one or more statements; an empty statement_list is not allowed. To handle situations where no value is matched by any WHEN clause, use an ELSE containing an empty BEGIN ... END block, as shown in this example:

DELIMITER |
CREATE PROCEDURE p()
BEGIN
  DECLARE v INT DEFAULT 1;
  CASE v
    WHEN 2 THEN SELECT v;
    WHEN 3 THEN SELECT 0;
    ELSE BEGIN END;
  END CASE;
END;
|

The indentation used here in the ELSE clause is for purposes of clarity only, and is not otherwise significant. See Delimiters in the mysql client for more on the use of the delimiter command.

Note: The syntax of the CASE statement used inside stored programs differs slightly from that of the SQL CASE expression described in CASE OPERATOR. The CASE statement cannot have an ELSE NULL clause, and it is terminated with END CASE instead of END.

1.1.1.6.4 DECLARE CONDITION

Syntax

DECLARE condition_name CONDITION FOR condition_value

condition_value:
    SQLSTATE [VALUE] sqlstate_value
  | mysql_error_code

Description

The DECLARE ... CONDITION statement defines a named error condition. It specifies a condition that needs specific handling and associates a name with that condition. Later, the name can be used in a DECLARE ... HANDLER, SIGNAL or RESIGNAL statement (as long as the statement is located in the same BEGIN ... END block).

Conditions must be declared after local variables, but before CURSORs and HANDLERs.

A condition_value for DECLARE ... CONDITION can be an SQLSTATE value (a 5-character string literal) or a MySQL error code (a number). You should not use SQLSTATE value '00000' or MySQL error code 0, because those indicate sucess rather than an error condition. If you try, or if you specify an invalid SQLSTATE value, an error like this is produced:

ERROR 1407 (42000): Bad SQLSTATE: '00000'

For a list of SQLSTATE values and MariaDB error codes, see MariaDB Error Codes.

1.1.1.6.5 DECLARE HANDLER

Syntax

DECLARE handler_type HANDLER
    FOR condition_value [, condition_value] ...
    statement

handler_type:
    CONTINUE
  | EXIT 
  | UNDO

condition_value:
    SQLSTATE [VALUE] sqlstate_value
  | condition_name
  | SQLWARNING
  | NOT FOUND
  | SQLEXCEPTION
  | mariadb_error_code

Description

The DECLARE ... HANDLER statement specifies handlers that each may deal with one or more conditions. If one of these conditions occurs, the specified statement is executed. statement can be a simple statement (for example, SET var_name = value), or it can be a compound statement written using BEGIN and END.

Handlers must be declared after local variables, a CONDITION and a CURSOR.

For a CONTINUE handler, execution of the current program continues after execution of the handler statement. For an EXIT handler, execution terminates for the BEGIN ... END compound statement in which the handler is declared. (This is true even if the condition occurs in an inner block.) The UNDO handler type statement is not supported.

If a condition occurs for which no handler has been declared, the default action is EXIT.

A condition_value for DECLARE ... HANDLER can be any of the following values:

  • An SQLSTATE value (a 5-character string literal) or a MariaDB error code (a number). You should not use SQLSTATE value '00000' or MariaDB error code 0, because those indicate sucess rather than an error condition. For a list of SQLSTATE values and MariaDB error codes, see MariaDB Error Codes.
  • A condition name previously specified with DECLARE ... CONDITION. It must be in the same stored program. See DECLARE CONDITION.
  • SQLWARNING is shorthand for the class of SQLSTATE values that begin with '01'.
  • NOT FOUND is shorthand for the class of SQLSTATE values that begin with '02'. This is relevant only the context of cursors and is used to control what happens when a cursor reaches the end of a data set. If no more rows are available, a No Data condition occurs with SQLSTATE value 02000. To detect this condition, you can set up a handler for it (or for a NOT FOUND condition). An example is shown in Cursor Overview. This condition also occurs for SELECT ... INTO var_list statements that retrieve no rows.
  • SQLEXCEPTION is shorthand for the class of SQLSTATE values that do not begin with '00', '01', or '02'.

When an error raises, in some cases it could be handled by multiple HANDLERs. For example, there may be an handler for 1050 error, a separate handler for the 42S01 SQLSTATE, and another separate handler for the SQLEXCEPTION class: in theory all occurrences of HANDLER may catch the 1050 error, but MariaDB chooses the HANDLER with the highest precedence. Here are the precedence rules:

  • Handlers which refer to an error code have the highest precedence.
  • Handlers which refer to a SQLSTATE come next.
  • Handlers which refer to an error class have the lowest precedence.

In some cases, a statement could produce multiple errors. If this happens, in some cases multiple handlers could have the highest precedence. In such cases, the choice of the handler is indeterminate.

Note that if an error occurs within a CONTINUE HANDLER block, it can be handled by another HANDLER. However, a HANDLER which is already in the stack (that is, it has been called to handle an error and its execution didn't finish yet) cannot handle new errors—this prevents endless loops. For example, suppose that a stored procedure contains a CONTINUE HANDLER for SQLWARNING and another CONTINUE HANDLER for NOT FOUND. At some point, a NOT FOUND error occurs, and the execution enters the NOT FOUND HANDLER. But within that handler, a warning occurs, and the execution enters the SQLWARNING HANDLER. If another NOT FOUND error occurs, it cannot be handled again by the NOT FOUND HANDLER, because its execution is not finished.

When a DECLARE HANDLER block can handle more than one error condition, it may be useful to know which errors occurred. To do so, you can use the GET DIAGNOSTICS statement.

An error that is handled by a DECLARE HANDLER construct can be issued again using the RESIGNAL statement.

Below is an example using DECLARE HANDLER:

CREATE TABLE test.t (s1 INT, PRIMARY KEY (s1));

DELIMITER //

CREATE PROCEDURE handlerdemo ( )
     BEGIN
       DECLARE CONTINUE HANDLER FOR SQLSTATE '23000' SET @x2 = 1;
       SET @x = 1;
       INSERT INTO test.t VALUES (1);
       SET @x = 2;
       INSERT INTO test.t VALUES (1);
       SET @x = 3;
     END;
     //

DELIMITER ;

CALL handlerdemo( );

SELECT @x;
+------+
| @x   |
+------+
|    3 |
+------+

1.1.1.6.6 DECLARE Variable

Syntax

DECLARE var_name [, var_name] ... [[ROW] TYPE OF]] type [DEFAULT value]

Contents

  1. Syntax
  2. Description
    1. TYPE OF / ROW TYPE OF
  3. Examples
  4. See Also

Description

This statement is used to declare local variables within stored programs. To provide a default value for the variable, include a DEFAULT clause. The value can be specified as an expression (even subqueries are permitted); it need not be a constant. If the DEFAULT clause is missing, the initial value is NULL.

Local variables are treated like stored routine parameters with respect to data type and overflow checking. See CREATE PROCEDURE.

Local variables must be declared before CONDITIONs, CURSORs and HANDLERs.

Local variable names are not case sensitive.

The scope of a local variable is within the BEGIN ... END block where it is declared. The variable can be referred to in blocks nested within the declaring block, except those blocks that declare a variable with the same name.

TYPE OF / ROW TYPE OF

MariaDB starting with 10.3

TYPE OF and ROW TYPE OF anchored data types for stored routines were introduced in MariaDB 10.3.

Anchored data types allow a data type to be defined based on another object, such as a table row, rather than specifically set in the declaration. If the anchor object changes, so will the anchored data type. This can lead to routines being easier to maintain, so that if the data type in the table is changed, it will automatically be changed in the routine as well.

Variables declared with ROW TYPE OF will have the same features as implicit ROW variables. It is not possible to use ROW TYPE OF variables in a LIMIT clause.

The real data type of TYPE OF and ROW TYPE OF table_name will become known at the very beginning of the stored routine call. ALTER TABLE or DROP TABLE statements performed inside the current routine on the tables that appear in anchors won't affect the data type of the anchored variables, even if the variable is declared after an ALTER TABLE or DROP TABLE statement.

The real data type of a ROW TYPE OF cursor_name variable will become known when execution enters into the block where the variable is declared. Data type instantiation will happen only once. In a cursor ROW TYPE OF variable that is declared inside a loop, its data type will become known on the very first iteration and won't change on further loop iterations.

The tables referenced in TYPE OF and ROW TYPE OF declarations will be checked for existence at the beginning of the stored routine call. CREATE PROCEDURE or CREATE FUNCTION will not check the referenced tables for existence.

Examples

TYPE OF and ROW TYPE OF from MariaDB 10.3:

DECLARE tmp TYPE OF t1.a; -- Get the data type from the column {{a}} in the table {{t1}}

DECLARE rec1 ROW TYPE OF t1; -- Get the row data type from the table {{t1}}

DECLARE rec2 ROW TYPE OF cur1; -- Get the row data type from the cursor {{cur1}}

See Also

1.1.1.6.7 FOR

MariaDB starting with 10.3

FOR loops were introduced in MariaDB 10.3.

Syntax

Integer range FOR loop:

[begin_label:]
FOR var_name IN [ REVERSE ] lower_bound .. upper_bound
DO statement_list
END FOR [ end_label ]

Explicit cursor FOR loop

[begin_label:]
FOR record_name IN cursor_name [ ( cursor_actual_parameter_list)]
DO statement_list
END FOR [ end_label ]

Explicit cursor FOR loop (Oracle mode)

[begin_label:]
FOR record_name IN cursor_name [ ( cursor_actual_parameter_list)]
LOOP
  statement_list
END LOOP [ end_label ]

Implicit cursor FOR loop

[begin_label:]
FOR record_name IN ( select_statement )
DO statement_list
END FOR [ end_label ]

Contents

  1. Syntax
  2. Description
  3. Examples
  4. See Also

Description

FOR loops allow code to be executed a fixed number of times.

In an integer range FOR loop, MariaDB will compare the lower bound and upper bound values, and assign the lower bound value to a counter. If REVERSE is not specified, and the upper bound value is greater than or equal to the counter, the counter will be incremented and the statement will continue, after which the loop is entered again. If the upper bound value is greater than the counter, the loop will be exited.

If REVERSE is specified, the counter is decremented, and the upper bound value needs to be less than or equal for the loop to continue.

Examples

Intger range FOR loop:

CREATE TABLE t1 (a INT);

DELIMITER //

FOR i IN 1..3
DO
  INSERT INTO t1 VALUES (i);
END FOR;
//

DELIMITER ;

SELECT * FROM t1;
+------+
| a    |
+------+
|    1 |
|    2 |
|    3 |
+------+

REVERSE integer range FOR loop:

CREATE OR REPLACE TABLE t1 (a INT);

DELIMITER //
FOR i IN REVERSE 4..12
    DO
    INSERT INTO t1 VALUES (i);
END FOR;
//
Query OK, 9 rows affected (0.422 sec)


DELIMITER ;

SELECT * FROM t1;
+------+
| a    |
+------+
|   12 |
|   11 |
|   10 |
|    9 |
|    8 |
|    7 |
|    6 |
|    5 |
|    4 |
+------+

Explicit cursor in Oracle mode:

SET sql_mode=ORACLE;

CREATE OR REPLACE TABLE t1 (a INT, b VARCHAR(32));

INSERT INTO t1 VALUES (10,'b0');
INSERT INTO t1 VALUES (11,'b1');
INSERT INTO t1 VALUES (12,'b2');

DELIMITER //

CREATE OR REPLACE PROCEDURE p1(pa INT) AS 
  CURSOR cur(va INT) IS
    SELECT a, b FROM t1 WHERE a=va;
BEGIN
  FOR rec IN cur(pa)
  LOOP
    SELECT rec.a, rec.b;
  END LOOP;
END;
//

DELIMITER ;

CALL p1(10);
+-------+-------+
| rec.a | rec.b |
+-------+-------+
|    10 | b0    |
+-------+-------+

CALL p1(11);
+-------+-------+
| rec.a | rec.b |
+-------+-------+
|    11 | b1    |
+-------+-------+

CALL p1(12);
+-------+-------+
| rec.a | rec.b |
+-------+-------+
|    12 | b2    |
+-------+-------+

CALL p1(13);
Query OK, 0 rows affected (0.000 sec)

See Also

1.1.1.6.8 GOTO

MariaDB starting with 10.3

The GOTO statement was introduced in MariaDB 10.3 for Oracle compatibility.

Syntax

GOTO label

Contents

  1. Syntax
  2. Description
  3. Example

Description

The GOTO statement causes the code to jump to the specified label, and continue operating from there. It is only accepted when in Oracle mode.

Example

SET sql_mode=ORACLE;

DELIMITER //

CREATE OR REPLACE PROCEDURE p1 AS

BEGIN

  SELECT 1;
  GOTO label;
  SELECT 2;
  <<label>>
  SELECT 3;

END;

//

DELIMITER 

call p1();
+---+
| 1 |
+---+
| 1 |
+---+
1 row in set (0.000 sec)

+---+
| 3 |
+---+
| 3 |
+---+
1 row in set (0.000 sec)

1.1.1.6.9 IF

Syntax

IF search_condition THEN statement_list
    [ELSEIF search_condition THEN statement_list] ...
    [ELSE statement_list]
END IF;

Description

IF implements a basic conditional construct. If the search_condition evaluates to true, the corresponding SQL statement list is executed. If no search_condition matches, the statement list in the ELSE clause is executed. Each statement_list consists of one or more statements.

See Also

1.1.1.6.10 ITERATE

Syntax

ITERATE label

ITERATE can appear only within LOOP, REPEAT, and WHILE statements. ITERATE means "do the loop again", and uses the statement's label to determine which statements to repeat. The label must be in the same stored program, not in a caller procedure.

If you try to use ITERATE with a non-existing label, or if the label is associated to a construct which is not a loop, the following error will be produced:

ERROR 1308 (42000): ITERATE with no matching label: <label_name>

Below is an example of how ITERATE might be used:

CREATE PROCEDURE doiterate(p1 INT)
BEGIN
  label1: LOOP
    SET p1 = p1 + 1;
    IF p1 < 10 THEN ITERATE label1; END IF;
    LEAVE label1;
  END LOOP label1;
  SET @x = p1;
END

See Also

  • LEAVE - Exits a loop (or any labeled code block)

1.1.1.6.11 Labels

Syntax

label: <construct>
[label]

Labels are MariaDB identifiers which can be used to identify a BEGIN ... END construct or a loop. They have a maximum length of 16 characters and can be quoted with backticks (i.e.., `).

Labels have a start part and an end part. The start part must precede the portion of code it refers to, must be followed by a colon (:) and can be on the same or different line. The end part is optional and adds nothing, but can make the code more readable. If used, the end part must precede the construct's delimiter (;). Constructs identified by a label can be nested. Each construct can be identified by only one label.

Labels need not be unique in the stored program they belong to. However, a label for an inner loop cannot be identical to a label for an outer loop. In this case, the following error would be produced:

ERROR 1309 (42000): Redefining label <label_name>

LEAVE and ITERATE statements can be used to exit or repeat a portion of code identified by a label. They must be in the same Stored Routine, Trigger or Event which contains the target label.

Below is an example using a simple label that is used to exit a LOOP:

CREATE PROCEDURE `test_sp`()
BEGIN
   `my_label`:
   LOOP
      SELECT 'looping';
      LEAVE `my_label`;
   END LOOP;
   SELECT 'out of loop';
END;

The following label is used to exit a procedure, and has an end part:

CREATE PROCEDURE `test_sp`()
`my_label`:
BEGIN
   IF @var = 1 THEN
      LEAVE `my_label`;
   END IF;
   DO something();
END `my_label`;

1.1.1.6.12 LEAVE

Syntax

LEAVE label

This statement is used to exit the flow control construct that has the given label. The label must be in the same stored program, not in a caller procedure. LEAVE can be used within BEGIN ... END or loop constructs (LOOP, REPEAT, WHILE). In Stored Procedures, Triggers and Events, LEAVE can refer to the outmost BEGIN ... END construct; in that case, the program exits the procedure. In Stored Functions, RETURN can be used instead.

Note that LEAVE cannot be used to exit a DECLARE HANDLER block.

If you try to LEAVE a non-existing label, or if you try to LEAVE a HANDLER block, the following error will be produced:

ERROR 1308 (42000): LEAVE with no matching label: <label_name>

The following example uses LEAVE to exit the procedure if a condition is true:

CREATE PROCEDURE proc(IN p TINYINT)
CONTAINS SQL
`whole_proc`:
BEGIN
   SELECT 1;
   IF p < 1 THEN
      LEAVE `whole_proc`;
   END IF;
   SELECT 2;
END;

CALL proc(0);
+---+
| 1 |
+---+
| 1 |
+---+

See Also

1.1.1.6.13 LOOP

Syntax

[begin_label:] LOOP
    statement_list
END LOOP [end_label]

Contents

  1. Syntax
  2. Description
  3. See Also

Description

LOOP implements a simple loop construct, enabling repeated execution of the statement list, which consists of one or more statements, each terminated by a semicolon (i.e., ;) statement delimiter. The statements within the loop are repeated until the loop is exited; usually this is accomplished with a LEAVE statement.

A LOOP statement can be labeled. end_label cannot be given unless begin_label also is present. If both are present, they must be the same.

See Delimiters in the mysql client for more on delimiter usage in the client.

See Also

1.1.1.6.14 REPEAT LOOP

Syntax

[begin_label:] REPEAT
    statement_list
UNTIL search_condition
END REPEAT [end_label]

The statement list within a REPEAT statement is repeated until the search_condition is true. Thus, a REPEAT always enters the loop at least once. statement_list consists of one or more statements, each terminated by a semicolon (i.e., ;) statement delimiter.

A REPEAT statement can be labeled. end_label cannot be given unless begin_label also is present. If both are present, they must be the same.

See Delimiters in the mysql client for more on client delimiter usage.

DELIMITER //

CREATE PROCEDURE dorepeat(p1 INT)
  BEGIN
    SET @x = 0;
    REPEAT SET @x = @x + 1; UNTIL @x > p1 END REPEAT;
  END
//

CALL dorepeat(1000)//

SELECT @x//
+------+
| @x   |
+------+
| 1001 |
+------+

1.1.1.6.15 RESIGNAL

Syntax

RESIGNAL [error_condition]
    [SET error_property
    [, error_property] ...]

error_condition:
    SQLSTATE [VALUE] 'sqlstate_value'
  | condition_name

error_property:
    error_property_name = <error_property_value>

error_property_name:
    CLASS_ORIGIN
  | SUBCLASS_ORIGIN
  | MESSAGE_TEXT
  | MYSQL_ERRNO
  | CONSTRAINT_CATALOG
  | CONSTRAINT_SCHEMA
  | CONSTRAINT_NAME
  | CATALOG_NAME
  | SCHEMA_NAME
  | TABLE_NAME
  | COLUMN_NAME
  | CURSOR_NAME

Contents

  1. Syntax
  2. Description
  3. See Also

Description

The syntax of RESIGNAL and its semantics are very similar to SIGNAL. This statement can only be used within an error HANDLER. It produces an error, like SIGNAL. RESIGNAL clauses are the same as SIGNAL, except that they all are optional, even SQLSTATE. All the properties which are not specified in RESIGNAL, will be identical to the properties of the error that was received by the error HANDLER. For a description of the clauses, see diagnostics area.

Note that RESIGNAL does not empty the diagnostics area: it just appends another error condition.

RESIGNAL, without any clauses, produces an error which is identical to the error that was received by HANDLER.

If used out of a HANDLER construct, RESIGNAL produces the following error:

ERROR 1645 (0K000): RESIGNAL when handler not active

In MariaDB 5.5, if a HANDLER contained a CALL to another procedure, that procedure could use RESIGNAL. Since MariaDB 10.0, trying to do this raises the above error.

For a list of SQLSTATE values and MariaDB error codes, see MariaDB Error Codes.

The following procedure tries to query two tables which don't exist, producing a 1146 error in both cases. Those errors will trigger the HANDLER. The first time the error will be ignored and the client will not receive it, but the second time, the error is re-signaled, so the client will receive it.

CREATE PROCEDURE test_error( )
BEGIN
   DECLARE CONTINUE HANDLER
      FOR 1146
   BEGIN
   IF @hide_errors IS FALSE THEN
      RESIGNAL;
   END IF;
   END;
   SET @hide_errors = TRUE;
   SELECT 'Next error will be ignored' AS msg;
   SELECT `c` FROM `temptab_one`;
   SELECT 'Next error won''t be ignored' AS msg;
   SET @hide_errors = FALSE;
   SELECT `c` FROM `temptab_two`;
END;

CALL test_error( );

+----------------------------+
| msg                        |
+----------------------------+
| Next error will be ignored |
+----------------------------+

+-----------------------------+
| msg                         |
+-----------------------------+
| Next error won't be ignored |
+-----------------------------+

ERROR 1146 (42S02): Table 'test.temptab_two' doesn't exist

The following procedure re-signals an error, modifying only the error message to clarify the cause of the problem.

CREATE PROCEDURE test_error()
BEGIN
   DECLARE CONTINUE HANDLER
   FOR 1146
   BEGIN
      RESIGNAL SET
      MESSAGE_TEXT = '`temptab` does not exist';
   END;
   SELECT `c` FROM `temptab`;
END;

CALL test_error( );
ERROR 1146 (42S02): `temptab` does not exist

As explained above, this works on MariaDB 5.5, but produces a 1645 error since 10.0.

CREATE PROCEDURE handle_error()
BEGIN
  RESIGNAL;
END;
CREATE PROCEDURE p()
BEGIN
  DECLARE EXIT HANDLER FOR SQLEXCEPTION CALL p();
  SIGNAL SQLSTATE '45000';
END;

See Also

1.1.1.6.16 RETURN

Syntax

RETURN expr

The RETURN statement terminates execution of a stored function and returns the value expr to the function caller. There must be at least one RETURN statement in a stored function. If the function has multiple exit points, all exit points must have a RETURN.

This statement is not used in stored procedures, triggers, or events. LEAVE can be used instead.

The following example shows that RETURN can return the result of a scalar subquery:

CREATE FUNCTION users_count() RETURNS BOOL
   READS SQL DATA
BEGIN
   RETURN (SELECT COUNT(DISTINCT User) FROM mysql.user);
END;

1.1.1.6.17 SELECT INTO

Syntax

SELECT col_name [, col_name] ...
    INTO var_name [, var_name] ...
    table_expr

Contents

  1. Syntax
  2. Description
  3. Examples
  4. See Also

Description

SELECT ... INTO enables selected columns to be stored directly into variables. No resultset is produced. The query should return a single row. If the query returns no rows, a warning with error code 1329 occurs (No data), and the variable values remain unchanged. If the query returns multiple rows, error 1172 occurs (Result consisted of more than one row). If it is possible that the statement may retrieve multiple rows, you can use LIMIT 1 to limit the result set to a single row.

The INTO clause can also be specified at the end of the statement.

In the context of such statements that occur as part of events executed by the Event Scheduler, diagnostics messages (not only errors, but also warnings) are written to the error log, and, on Windows, to the application event log.

This statement can be used with both local variables and user-defined variables.

For the complete syntax, see SELECT.

Another way to set a variable's value is the SET statement.

SELECT ... INTO results are not stored in the query cache even if SQL_CACHE is specified.

Examples

SELECT id, data INTO @x,@y 
FROM test.t1 LIMIT 1;

See Also

1.1.1.6.18 SET Variable

1.1.1.6.19 SIGNAL

Syntax

SIGNAL error_condition
    [SET error_property
    [, error_property] ...]

error_condition:
    SQLSTATE [VALUE] 'sqlstate_value'
  | condition_name

error_property:
    error_property_name = <error_property_value>

error_property_name:
    CLASS_ORIGIN
  | SUBCLASS_ORIGIN
  | MESSAGE_TEXT
  | MYSQL_ERRNO
  | CONSTRAINT_CATALOG
  | CONSTRAINT_SCHEMA
  | CONSTRAINT_NAME
  | CATALOG_NAME
  | SCHEMA_NAME
  | TABLE_NAME
  | COLUMN_NAME
  | CURSOR_NAME

Contents

  1. Syntax
  2. Errors
  3. Examples
  4. See Also

SIGNAL empties the diagnostics area and produces a custom error. This statement can be used anywhere, but is generally useful when used inside a stored program. When the error is produced, it can be caught by a HANDLER. If not, the current stored program, or the current statement, will terminate with the specified error.

Sometimes an error HANDLER just needs to SIGNAL the same error it received, optionally with some changes. Usually the RESIGNAL statement is the most convenient way to do this.

error_condition can be an SQLSTATE value or a named error condition defined via DECLARE CONDITION. SQLSTATE must be a constant string consisting of five characters. These codes are standard to ODBC and ANSI SQL. For customized errors, the recommended SQLSTATE is '45000'. For a list of SQLSTATE values used by MariaDB, see the MariaDB Error Codes page. The SQLSTATE can be read via the API method mysql_sqlstate( ).

To specify error properties user-defined variables and local variables can be used, as well as character set conversions (but you can't set a collation).

The error properties, their type and their default values are explained in the diagnostics area page.

Errors

If the SQLSTATE is not valid, the following error like this will be produced:

ERROR 1407 (42000): Bad SQLSTATE: '123456'

If a property is specified more than once, an error like this will be produced:

ERROR 1641 (42000): Duplicate condition information item 'MESSAGE_TEXT'

If you specify a condition name which is not declared, an error like this will be produced:

ERROR 1319 (42000): Undefined CONDITION: cond_name

If MYSQL_ERRNO is out of range, you will get an error like this:

ERROR 1231 (42000): Variable 'MYSQL_ERRNO' can't be set to the value of '0'

Examples

Here's what happens if SIGNAL is used in the client to generate errors:

SIGNAL SQLSTATE '01000';
Query OK, 0 rows affected, 1 warning (0.00 sec)

SHOW WARNINGS;

+---------+------+------------------------------------------+
| Level   | Code | Message                                  |
+---------+------+------------------------------------------+
| Warning | 1642 | Unhandled user-defined warning condition |
+---------+------+------------------------------------------+
1 row in set (0.06 sec)

SIGNAL SQLSTATE '02000';
ERROR 1643 (02000): Unhandled user-defined not found condition

How to specify MYSQL_ERRNO and MESSAGE_TEXT properties:

SIGNAL SQLSTATE '45000' SET MYSQL_ERRNO=30001, MESSAGE_TEXT='H
ello, world!';

ERROR 30001 (45000): Hello, world!

The following code shows how to use user variables, local variables and character set conversion with SIGNAL:

CREATE PROCEDURE test_error(x INT)
BEGIN
   DECLARE errno SMALLINT UNSIGNED DEFAULT 31001;
   SET @errmsg = 'Hello, world!';
   IF x = 1 THEN
      SIGNAL SQLSTATE '45000' SET
      MYSQL_ERRNO = errno,
      MESSAGE_TEXT = @errmsg;
   ELSE
      SIGNAL SQLSTATE '45000' SET
      MYSQL_ERRNO = errno,
      MESSAGE_TEXT = _utf8'Hello, world!';
   END IF;
END;

How to use named error conditions:

CREATE PROCEDURE test_error(n INT)
BEGIN
   DECLARE `too_big` CONDITION FOR SQLSTATE '45000';
   IF n > 10 THEN
      SIGNAL `too_big`;
   END IF;
END;

In this example, we'll define a HANDLER for an error code. When the error occurs, we SIGNAL a more informative error which makes sense for our procedure:

CREATE PROCEDURE test_error()
BEGIN
   DECLARE EXIT HANDLER
   FOR 1146
   BEGIN
      SIGNAL SQLSTATE '45000' SET
      MESSAGE_TEXT = 'Temporary tables not found; did you call init() procedure?';
   END;
   -- this will produce a 1146 error
   SELECT `c` FROM `temptab`;
END;

See Also

1.1.1.6.20 WHILE

Syntax

[begin_label:] WHILE search_condition DO
    statement_list
END WHILE [end_label]

Description

The statement list within a WHILE statement is repeated as long as the search_condition is true. statement_list consists of one or more statements. If the loop must be executed at least once, REPEAT ... LOOP can be used instead.

A WHILE statement can be labeled. end_label cannot be given unless begin_label also is present. If both are present, they must be the same.

Examples

CREATE PROCEDURE dowhile()
BEGIN
  DECLARE v1 INT DEFAULT 5;

  WHILE v1 > 0 DO
    ...
    SET v1 = v1 - 1;
  END WHILE;
END

1.1.1.7 Stored Routine Statements

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1.1.1.7.1 CALL

Syntax

CALL sp_name([parameter[,...]])
CALL sp_name[()]

Description

The CALL statement invokes a stored procedure that was defined previously with CREATE PROCEDURE.

Stored procedure names can be specified as database_name.procedure_name. Procedure names and database names can be quoted with backticks (). This is necessary if they are reserved words, or contain special characters. See identifier qualifiers for details.

CALL p() and CALL p are equivalent.

If parentheses are used, any number of spaces, tab characters and newline characters are allowed between the procedure's name and the open parenthesis.

CALL can pass back values to its caller using parameters that are declared as OUT or INOUT parameters. If no value is assigned to an OUT parameter, NULL is assigned (and its former value is lost). To pass such values from another stored program you can use user-defined variables, local variables or routine's parameters; in other contexts, you can only use user-defined variables.

CALL can also be executed as a prepared statement. Placeholders can be used for IN parameters in all versions of MariaDB; for OUT and INOUT parameters, placeholders can be used since MariaDB 5.5.

When the procedure returns, a client program can also obtain the number of rows affected for the final statement executed within the routine: At the SQL level, call the ROW_COUNT() function; from the C API, call the mysql_affected_rows() function.

If the CLIENT_MULTI_RESULTS API flag is set, CALL can return any number of resultsets and the called stored procedure can execute prepared statements. If it is not set, at most one resultset can be returned and prepared statements cannot be used within procedures.

1.1.1.7.2 DO

Syntax

DO expr [, expr] ...

Description

DO executes the expressions but does not return any results. In most respects, DO is shorthand for SELECT expr, ..., but has the advantage that it is slightly faster when you do not care about the result.

DO is useful primarily with functions that have side effects, such as RELEASE_LOCK().

1.1.1.8 Table Statements

1.1.1.9 Transactions

"An SQL-transaction (transaction) is a sequence of executions of SQL-statements that is atomic with respect to recovery. That is to say: either the execution result is completely successful, or it has no effect on any SQL-schemas or SQL-data."

— The SQL Standard

The InnoDB storage engine supports ACID-compliant transactions.

Transaction Articles

1.1.1.9.1 START TRANSACTION

Syntax

START TRANSACTION [transaction_property [, transaction_property] ...] | BEGIN [WORK]
COMMIT [WORK] [AND [NO] CHAIN] [[NO] RELEASE]
ROLLBACK [WORK] [AND [NO] CHAIN] [[NO] RELEASE]
SET autocommit = {0 | 1}

transaction_property:
    WITH CONSISTENT SNAPSHOT
  | READ WRITE
  | READ ONLY

Contents

  1. Syntax
  2. Description
    1. Access Mode
    2. autocommit
    3. DDL Statements
    4. in_transaction
    5. WITH CONSISTENT SNAPSHOT
  3. Examples
  4. See Also

Description

The START TRANSACTION or BEGIN statement begins a new transaction. COMMIT commits the current transaction, making its changes permanent. ROLLBACK rolls back the current transaction, canceling its changes. The SET autocommit statement disables or enables the default autocommit mode for the current session.

START TRANSACTION and SET autocommit = 1 implicitly commit the current transaction, if any.

The optional WORK keyword is supported for COMMIT and ROLLBACK, as are the CHAIN and RELEASE clauses. CHAIN and RELEASE can be used for additional control over transaction completion. The value of the completion_type system variable determines the default completion behavior.

The AND CHAIN clause causes a new transaction to begin as soon as the current one ends, and the new transaction has the same isolation level as the just-terminated transaction. The RELEASE clause causes the server to disconnect the current client session after terminating the current transaction. Including the NO keyword suppresses CHAIN or RELEASE completion, which can be useful if the completion_type system variable is set to cause chaining or release completion by default.

Access Mode

The access mode specifies whether the transaction is allowed to write data or not. By default, transactions are in READ WRITE mode (see the tx_read_only system variable). READ ONLY mode allows the storage engine to apply optimizations that cannot be used for transactions which write data. The only exception to this rule is that read only transactions can perform DDL statements on temporary tables.

It is not permitted to specify both READ WRITE and READ ONLY in the same statement.

READ WRITE and READ ONLY can also be specified in the SET TRANSACTION statement, in which case the specified mode is valid for all sessions, or for all subsequent transaction used by the current session.

autocommit

By default, MariaDB runs with autocommit mode enabled. This means that as soon as you execute a statement that updates (modifies) a table, MariaDB stores the update on disk to make it permanent. To disable autocommit mode, use the following statement:

SET autocommit=0;

After disabling autocommit mode by setting the autocommit variable to zero, changes to transaction-safe tables (such as those for InnoDB or NDBCLUSTER) are not made permanent immediately. You must use COMMIT to store your changes to disk or ROLLBACK to ignore the changes.

To disable autocommit mode for a single series of statements, use the START TRANSACTION statement.

DDL Statements

DDL statements (CREATE, ALTER, DROP) and administrative statements (FLUSH, RESET, OPTIMIZE, ANALYZE, CHECK, REPAIR, CACHE INDEX), transaction management statements (BEGIN, START TRANSACTION) and LOAD DATA INFILE, cause an implicit COMMIT and start a new transaction. An exception to this rule are the DDL that operate on temporary tables: you can CREATE, ALTER and DROP them without causing any COMMIT, but those actions cannot be rolled back. This means that if you call ROLLBACK, the temporary tables you created in the transaction will remain, while the rest of the transaction will be rolled back.

Transactions cannot be used in Stored Functions or Triggers. In Stored Procedures and Events BEGIN is not allowed, so you should use START TRANSACTION instead.

A transaction acquires a metadata lock on every table it accesses to prevent other connections from altering their structure. The lock is released at the end of the transaction. This happens even with non-transactional storage engines (like MEMORY or CONNECT), so it makes sense to use transactions with non-transactional tables.

in_transaction

The in_transaction system variable is a session-only, read-only variable that returns 1 inside a transaction, and 0 if not in a transaction.

WITH CONSISTENT SNAPSHOT

The WITH CONSISTENT SNAPSHOT option starts a consistent read for storage engines such as InnoDB that can do so, the same as if a START TRANSACTION followed by a SELECT from any InnoDB table was issued.

See Enhancements for START TRANSACTION WITH CONSISTENT SNAPSHOT.

Examples

START TRANSACTION;
SELECT @A:=SUM(salary) FROM table1 WHERE type=1;
UPDATE table2 SET summary=@A WHERE type=1;
COMMIT;

See Also

1.1.1.9.2 COMMIT

The COMMIT statement ends a transaction, saving any changes to the data so that they become visible to subsequent transactions. Also, unlocks metadata changed by current transaction. If autocommit is set to 1, an implicit commit is performed after each statement. Otherwise, all transactions which don't end with an explicit COMMIT are implicitly rollbacked and the changes are lost. The ROLLBACK statement can be used to do this explicitly.

The required syntax for the COMMIT statement is as follows:

COMMIT [WORK] [AND [NO] CHAIN] [[NO] RELEASE]

COMMIT is the more important transaction terminator, as well as the more interesting one. The basic form of the COMMIT statement is simply the keyword COMMIT (the keyword WORK is simply noise and can be omitted without changing the effect).

The optional AND CHAIN clause is a convenience for initiating a new transaction as soon as the old transaction terminates. If AND CHAIN is specified, then there is effectively nothing between the old and new transactions, although they remain separate. The characteristics of the new transaction will be the same as the characteristics of the old one — that is, the new transaction will have the same access mode, isolation level and diagnostics area size (we'll discuss all of these shortly) as the transaction just terminated.

RELEASE tells the server to disconnect the client immediately after the current transaction.

There are NO RELEASE and AND NO CHAIN options. By default, commits do not RELEASE or CHAIN, but it's possible to change this default behavior with the completion_type server system variable. In this case, the AND NO CHAIN and NO RELEASE options override the server default.

See Also

1.1.1.9.3 ROLLBACK

The ROLLBACK statement rolls back (ends) a transaction, destroying any changes to SQL-data so that they never become visible to subsequent transactions. The required syntax for the ROLLBACK statement is as follows. 

ROLLBACK [ WORK ] [ AND [ NO ] CHAIN ] 
[ TO [ SAVEPOINT ] {<savepoint name> | <simple target specification>} ]

The ROLLBACK statement will either end a transaction, destroying all data changes that happened during any of the transaction, or it will just destroy any data changes that happened since you established a savepoint. The basic form of the ROLLBACK statement is just the keyword ROLLBACK (the keyword WORK is simply noise and can be omitted without changing the effect).

The optional AND CHAIN clause is a convenience for initiating a new transaction as soon as the old transaction terminates. If AND CHAIN is specified, then there is effectively nothing between the old and new transactions, although they remain separate. The characteristics of the new transaction will be the same as the characteristics of the old one — that is, the new transaction will have the same access mode, isolation level and diagnostics area size (we'll discuss all of these shortly) as the transaction just terminated. The AND NO CHAIN option just tells your DBMS to end the transaction — that is, these four SQL statements are equivalent: 

ROLLBACK; 
ROLLBACK WORK; 
ROLLBACK AND NO CHAIN; 
ROLLBACK WORK AND NO CHAIN;

All of them end a transaction without saving any transaction characteristics. The only other options, the equivalent statements: 

ROLLBACK AND CHAIN;
ROLLBACK WORK AND CHAIN;

both tell your DBMS to end a transaction, but to save that transaction's characteristics for the next transaction.

ROLLBACK is much simpler than COMMIT: it may involve no more than a few deletions (of Cursors, locks, prepared SQL statements and log-file entries). It's usually assumed that ROLLBACK can't fail, although such a thing is conceivable (for example, an encompassing transaction might reject an attempt to ROLLBACK because it's lining up for a COMMIT).

ROLLBACK cancels all effects of a transaction. It does not cancel effects on objects outside the DBMS's control (for example the values in host program variables or the settings made by some SQL/CLI function calls). But in general, it is a convenient statement for those situations when you say "oops, this isn't working" or when you simply don't care whether your temporary work becomes permanent or not.

Here is a moot question. If all you've been doing is SELECTs, so that there have been no data changes, should you end the transaction with ROLLBACK or COMMIT? It shouldn't really matter because both ROLLBACK and COMMIT do the same transaction-terminating job. However, the popular conception is that ROLLBACK implies failure, so after a successful series of SELECT statements the convention is to end the transaction with COMMIT rather than ROLLBACK.

MariaDB (and most other DBMSs) supports rollback of SQL-data change statements, but not of SQL-Schema statements. This means that if you use any of CREATE, ALTER, DROP, GRANT, REVOKE, you are implicitly committing at execution time.

INSERT INTO Table_2 VALUES(5); 
DROP TABLE Table_3 CASCADE; 
ROLLBACK;

The result will be that both the INSERT and the DROP will go through as separate transactions so the ROLLBACK will have no effect.

1.1.1.9.4 SET TRANSACTION

1.1.1.9.5 LOCK TABLES

Syntax

LOCK TABLE[S]
    tbl_name [[AS] alias] lock_type
    [, tbl_name [[AS] alias] lock_type] ...
    [WAIT n|NOWAIT]

lock_type:
    READ [LOCAL]
  | [LOW_PRIORITY] WRITE
  | WRITE CONCURRENT

UNLOCK TABLES

Contents

  1. Syntax
  2. Description
    1. WAIT/NOWAIT
  3. Limitations
  4. See Also

Description

The lock_type can be one of:

OptionDescription
READRead lock, no writes allowed
READ LOCALRead lock, but allow concurrent inserts
WRITEExclusive write lock. No other connections can read or write to this table
LOW_PRIORITY WRITEExclusive write lock, but allow new read locks on the table until we get the write lock.
WRITE CONCURRENTExclusive write lock, but allow READ LOCAL locks to the table.

MariaDB enables client sessions to acquire table locks explicitly for the purpose of cooperating with other sessions for access to tables, or to prevent other sessions from modifying tables during periods when a session requires exclusive access to them. A session can acquire or release locks only for itself. One session cannot acquire locks for another session or release locks held by another session.

Locks may be used to emulate transactions or to get more speed when updating tables.

LOCK TABLES explicitly acquires table locks for the current client session. Table locks can be acquired for base tables or views. To use LOCK TABLES, you must have the LOCK TABLES privilege, and the SELECT privilege for each object to be locked. See GRANT

For view locking, LOCK TABLES adds all base tables used in the view to the set of tables to be locked and locks them automatically. If you lock a table explicitly with LOCK TABLES, any tables used in triggers are also locked implicitly, as described in Triggers and Implicit Locks.

UNLOCK TABLES explicitly releases any table locks held by the current session.

MariaDB starting with 10.3.0

WAIT/NOWAIT

Set the lock wait timeout. See WAIT and NOWAIT.

Limitations

  • LOCK TABLES doesn't work when using Galera cluster. You may experience crashes or locks when used with Galera.
  • LOCK TABLES works on XtraDB/InnoDB tables only if the innodb_table_locks system variable is set to 1 (the default) and autocommit is set to 0 (1 is default). Please note that no error message will be returned on LOCK TABLES with innodb_table_locks = 0.
  • LOCK TABLES implicitly commits the active transaction, if any. Also, starting a transaction always releases all table locks acquired with LOCK TABLES. This means that there is no way to have table locks and an active transaction at the same time. The only exceptions are the transactions in autocommit mode. To preserve the data integrity between transactional and non-transactional tables, the GET_LOCK() function can be used.
  • When using LOCK TABLES on a TEMPORARY table, it will always be locked with a WRITE lock.
  • While a connection holds an explicit read lock on a table, it cannot modify it. If you try, the following error will be produced: 
ERROR 1099 (HY000): Table 'tab_name' was locked with a READ lock and can't be updated
  • While a connection holds an explicit lock on a table, it cannot access a non-locked table. If you try, the following error will be produced: 
ERROR 1100 (HY000): Table 'tab_name' was not locked with LOCK TABLES
  • While a connection holds an explicit lock on a table, it cannot issue the following: INSERT DELAYED, CREATE TABLE, CREATE TABLE ... LIKE, and DDL statements involving stored programs and views (except for triggers). If you try, the following error will be produced: 
ERROR 1192 (HY000): Can't execute the given command because you have active locked tables or an active transaction
  • LOCK TABLES can not be used in stored routines - if you try, the following error will be produced on creation: 
ERROR 1314 (0A000): LOCK is not allowed in stored procedures

See Also

1.1.1.9.6 SAVEPOINT

Syntax

SAVEPOINT identifier
ROLLBACK [WORK] TO [SAVEPOINT] identifier
RELEASE SAVEPOINT identifier

Contents

  1. Syntax
  2. Description
  3. Errors

Description

InnoDB supports the SQL statements SAVEPOINT, ROLLBACK TO SAVEPOINT, RELEASE SAVEPOINT and the optional WORK keyword for ROLLBACK.

Each savepoint must have a legal MariaDB identifier. A savepoint is a named sub-transaction.

Normally ROLLBACK undoes the changes performed by the whole transaction. When used with the TO clause, it undoes the changes performed after the specified savepoint, and erases all subsequent savepoints. However, all locks that have been acquired after the save point will survive. RELEASE SAVEPOINT does not rollback or commit any changes, but removes the specified savepoint.

When the execution of a trigger or a stored function begins, it is not possible to use statements which reference a savepoint which was defined from out of that stored program.

When a COMMIT (including implicit commits) or a ROLLBACK statement (with no TO clause) is performed, they act on the whole transaction, and all savepoints are removed.

Errors

If COMMIT or ROLLBACK is issued and no transaction was started, no error is reported.

If SAVEPOINT is issued and no transaction was started, no error is reported but no savepoint is created. When ROLLBACK TO SAVEPOINT or RELEASE SAVEPOINT is called for a savepoint that does not exist, an error like this is issued:

ERROR 1305 (42000): SAVEPOINT svp_name does not exist

1.1.1.9.7 Metadata Locking

MariaDB supports metadata locking. This means that when a transaction (including XA transactions) uses a table, it locks its metadata until the end of transaction. Non-transactional tables are also locked, as well as views and objects which are related to locked tables/views (stored functions, triggers, etc). When a connection tries to use a DDL statement (like an ALTER TABLE) which modifies a table that is locked, that connection is queued, and has to wait until it's unlocked. Using savepoints and performing a partial rollback does not release metadata locks.

LOCK TABLES ... WRITE are also queued. Some wrong statements which produce an error may not need to wait for the lock to be freed.

The metadata lock's timeout is determined by the value of the lock_wait_timeout server system variable (in seconds). However, note that its default value is 31536000 (1 year, MariaDB <= 10.2.3), or 86400 (1 day, MariaDB >= 10.2.4). If this timeout is exceeded, the following error is returned:

ERROR 1205 (HY000): Lock wait timeout exceeded; try restarting transaction

If the metadata_lock_info plugin is installed, the Information Schema metadata_lock_info table stores information about existing metadata locks.

MariaDB starting with 10.5.2

From MariaDB 10.5, the Performance Schema metadata_locks table contains metadata lock information.

Example

Let's use the following MEMORY (non-transactional) table:

CREATE TABLE t (a INT) ENGINE = MEMORY;

Connection 1 starts a transaction, and INSERTs a row into t:

START TRANSACTION;

INSERT INTO t SET a=1;

t's metadata is now locked by connection 1. Connection 2 tries to alter t, but has to wait:

ALTER TABLE t ADD COLUMN b INT;

Connection 2's prompt is blocked now.

Now connection 1 ends the transaction:

COMMIT;

...and connection 2 finally gets the output of its command:

Query OK, 1 row affected (35.23 sec)
Records: 1  Duplicates: 0  Warnings: 0

1.1.1.9.8 SQL statements That Cause an Implicit Commit

Some SQL statements cause an implicit commit. As a rule of thumb, such statements are DDL statements. The same statements (except for SHUTDOWN) produce a 1400 error (SQLSTATE 'XAE09') if a XA transaction is in effect.

Here is the list:

ALTER DATABASE ... UPGRADE DATA DIRECTORY NAME
ALTER EVENT
ALTER FUNCTION
ALTER PROCEDURE
ALTER SERVER
ALTER TABLE
ALTER VIEW
ANALYZE TABLE
BEGIN
CACHE INDEX
CHANGE MASTER TO
CHECK TABLE
CREATE DATABASE
CREATE EVENT
CREATE FUNCTION
CREATE INDEX
CREATE PROCEDURE
CREATE ROLE
CREATE SERVER
CREATE TABLE
CREATE TRIGGER
CREATE USER
CREATE VIEW
DROP DATABASE
DROP EVENT
DROP FUNCTION
DROP INDEX
DROP PROCEDURE
DROP ROLE
DROP SERVER
DROP TABLE
DROP TRIGGER
DROP USER
DROP VIEW
FLUSH
GRANT
LOAD INDEX INTO CACHE
LOCK TABLES
OPTIMIZE TABLE
RENAME TABLE
RENAME USER
REPAIR TABLE
RESET
REVOKE
SET PASSWORD
SHUTDOWN
START SLAVE
START TRANSACTION
STOP SLAVE
TRUNCATE TABLE

SET autocommit = 1 causes an implicit commit if the value was 0.

All these statements cause an implicit commit before execution. This means that, even if the statement fails with an error, the transaction is committed. Some of them, like CREATE TABLE ... SELECT, also cause a commit immediatly after execution. Such statements couldn't be rollbacked in any case.

If you are not sure whether a statement has implicitly committed the current transaction, you can query the in_transaction server system variable.

Note that when a transaction starts (not in autocommit mode), all locks acquired with LOCK TABLES are released. And acquiring such locks always commits the current transaction. To preserve the data integrity between transactional and non-transactional tables, the GET_LOCK() function can be used.

Exceptions

These statements do not cause an implicit commit in the following cases:

  • CREATE TABLE and DROP TABLE, when the TEMPORARY keyword is used.
    • However, TRUNCATE TABLE causes an implicit commit even when used on a temporary table.
  • CREATE FUNCTION and DROP FUNCTION, when used to create a UDF (instead of a stored function). However, CREATE INDEX and DROP INDEX cause commits even when used with temporary tables.
  • UNLOCK TABLES causes a commit only if a LOCK TABLES was used on non-transactional tables.
  • START SLAVE, STOP SLAVE, RESET SLAVE and CHANGE MASTER TO only cause implicit commit since MariaDB 10.0.

1.1.1.9.9 Transaction Timeouts

MariaDB has always had the wait_timeout and interactive_timeout settings, which close connections after a certain period of inactivity.

However, these are by default set to a long wait period. In situations where transactions may be started, but not committed or rolled back, more granular control and a shorter timeout may be desirable so as to avoid locks being held for too long.

MariaDB 10.3 introduced three new variables to handle this situation.

These accept a time in seconds to time out, by closing the connection, transactions that are idle for longer than this period. By default all are set to zero, or no timeout.

idle_transaction_timeout affects all transactions, idle_write_transaction_timeout affects write transactions only and idle_readonly_transaction_timeout affects read transactions only. The latter two variables work independently. However, if either is set along with idle_transaction_timeout, the settings for idle_write_transaction_timeout or idle_readonly_transaction_timeout will take precedence.

Examples

SET SESSION idle_transaction_timeout=2;
BEGIN;
SELECT * FROM t;
Empty set (0.000 sec)
## wait 3 seconds
SELECT * FROM t;
ERROR 2006 (HY000): MySQL server has gone away

SET SESSION idle_write_transaction_timeout=2;
BEGIN;
SELECT * FROM t;
Empty set (0.000 sec)
## wait 3 seconds
SELECT * FROM t;
Empty set (0.000 sec)
INSERT INTO t VALUES(1);
## wait 3 seconds
SELECT * FROM t;
ERROR 2006 (HY000): MySQL server has gone away

SET SESSION idle_transaction_timeout=2, SESSION idle_readonly_transaction_timeout=10;
BEGIN;
SELECT * FROM t;
Empty set (0.000 sec)
 ## wait 3 seconds
SELECT * FROM t;
Empty set (0.000 sec)
## wait 11 seconds
SELECT * FROM t;
ERROR 2006 (HY000): MySQL server has gone away

1.1.1.9.10 UNLOCK TABLES

Syntax

UNLOCK TABLES

Contents

  1. Syntax
  2. Description

Description

UNLOCK TABLES explicitly releases any table locks held by the current session. See LOCK TABLES for more information.

In addition to releasing table locks acquired by the LOCK TABLES statement, the UNLOCK TABLES statement also releases the global read lock acquired by the FLUSH TABLES WITH READ LOCK statement. The FLUSH TABLES WITH READ LOCK statement is very useful for performing backups. See FLUSH for more information about FLUSH TABLES WITH READ LOCK.

1.1.1.9.11 WAIT and NOWAIT

MariaDB starting with 10.3.0

MariaDB 10.3.0 introduced extended syntax so that it is possible to set innodb_lock_wait_timeout and lock_wait_timeout for the following statements:

Syntax

ALTER TABLE tbl_name [WAIT n|NOWAIT] ...
CREATE ... INDEX ON tbl_name (index_col_name, ...) [WAIT n|NOWAIT] ...
DROP INDEX ... [WAIT n|NOWAIT]
DROP TABLE tbl_name [WAIT n|NOWAIT] ...
LOCK TABLE ... [WAIT n|NOWAIT]
OPTIMIZE TABLE tbl_name [WAIT n|NOWAIT]
RENAME TABLE tbl_name [WAIT n|NOWAIT] ...
SELECT ... FOR UPDATE [WAIT n|NOWAIT]
SELECT ... LOCK IN SHARE MODE [WAIT n|NOWAIT]
TRUNCATE TABLE tbl_name [WAIT n|NOWAIT]

Description

The lock wait timeout can be explicitly set in the statement by using either WAIT n (to set the wait in seconds) or NOWAIT, in which case the statement will immediately fail if the lock cannot be obtained. WAIT 0 is equivalent to NOWAIT.

See Also

1.1.1.9.12 XA Transactions

Contents

  1. Overview
  2. Internal XA vs External XA
  3. Transaction Coordinator Log
  4. Syntax
  5. XA RECOVER
  6. Examples
  7. Known Issues
    1. MariaDB Galera Cluster

Overview

The MariaDB XA implementation is based on the X/Open CAE document Distributed Transaction Processing: The XA Specification. This document is published by The Open Group and available at http://www.opengroup.org/public/pubs/catalog/c193.htm.

XA transactions are designed to allow distributed transactions, where a transaction manager (the application) controls a transaction which involves multiple resources. Such resources are usually DBMSs, but could be resources of any type. The whole set of required transactional operations is called a global transaction. Each subset of operations which involve a single resource is called a local transaction. XA used a 2-phases commit (2PC). With the first commit, the transaction manager tells each resource to prepare an effective commit, and waits for a confirm message. The changes are not still made effective at this point. If any of the resources encountered an error, the transaction manager will rollback the global transaction. If all resources communicate that the first commit is successful, the transaction manager can require a second commit, which makes the changes effective.

In MariaDB, XA transactions can only be used with storage engines that support them. At least InnoDB, TokuDB, SPIDER and MyRocks support them. For InnoDB, until MariaDB 10.2, XA transactions can be disabled by setting the innodb_support_xa server system variable to 0. From MariaDB 10.3, XA transactions are always supported.

Like regular transactions, XA transactions create metadata locks on accessed tables.

XA transactions require REPEATABLE READ as a minimum isolation level. However, distributed transactions should always use SERIALIZABLE.

Trying to start more than one XA transaction at the same time produces a 1400 error (SQLSTATE 'XAE09'). The same error is produced when attempting to start an XA transaction while a regular transaction is in effect. Trying to start a regular transaction while an XA transaction is in effect produces a 1399 error (SQLSTATE 'XAE07').

The statements that cause an implicit COMMIT for regular transactions produce a 1400 error (SQLSTATE 'XAE09') if a XA transaction is in effect.

Internal XA vs External XA

XA transactions are an overloaded term in MariaDB. If a storage engine is XA-capable, it can mean one or both of these:

  • It supports MariaDB's internal two-phase commit API. This is transparent to the user. Sometimes this is called "internal XA", since MariaDB's internal transaction coordinator log can handle coordinating these transactions.
  • It supports XA transactions, with the XA START, XA PREPARE, XA COMMIT, etc. statements. Sometimes this is called "external XA", since it requires the use of an external transaction coordinator to use this feature properly.

Transaction Coordinator Log

If you have two or more XA-capable storage engines enabled, then a transaction coordinator log must be available.

There are currently two implementations of the transaction coordinator log:

  • Binary log-based transaction coordinator log
  • Memory-mapped file-based transaction coordinator log

If the binary log is enabled on a server, then the server will use the binary log-based transaction coordinator log. Otherwise, it will use the memory-mapped file-based transaction coordinator log.

See Transaction Coordinator Log for more information.

Syntax

XA {START|BEGIN} xid [JOIN|RESUME]

XA END xid [SUSPEND [FOR MIGRATE]]

XA PREPARE xid

XA COMMIT xid [ONE PHASE]

XA ROLLBACK xid

XA RECOVER [FORMAT=['RAW'|'SQL']]

xid: gtrid [, bqual [, formatID ]]

The interface to XA transactions is a set of SQL statements starting with XA. Each statement changes a transaction's state, determining which actions it can perform. A transaction which does not exist is in the NON-EXISTING state.

XA START (or BEGIN) starts a transaction and defines its xid (a transaction identifier). The JOIN or RESUME keywords have no effect. The new transaction will be in ACTIVE state.

The xid can have 3 components, though only the first one is mandatory. gtrid is a quoted string representing a global transaction identifier. bqual is a quoted string representing a local transaction identifier. formatID is an unsigned integer indicating the format used for the first two components; if not specified, defaults to 1. MariaDB does not interpret in any way these components, and only uses them to identify a transaction. xids of transactions in effect must be unique.

XA END declares that the specified ACTIVE transaction is finished and it changes its state to IDLE. SUSPEND [FOR MIGRATE] has no effect.

XA PREPARE prepares an IDLE transaction for commit, changing its state to PREPARED. This is the first commit.

XA COMMIT definitely commits and terminates a transaction which has already been PREPARED. If the ONE PHASE clause is specified, this statements performs a 1-phase commit on an IDLE transaction.

XA ROLLBACK rolls back and terminates an IDLE or PREPARED transaction.

XA RECOVER shows information about all PREPARED transactions.

When trying to execute an operation which is not allowed for the transaction's current state, an error is produced:

XA COMMIT 'test' ONE PHASE;
ERROR 1399 (XAE07): XAER_RMFAIL: The command cannot be executed when global transaction is in the  ACTIVE state

XA COMMIT 'test2';
ERROR 1399 (XAE07): XAER_RMFAIL: The command cannot be executed when global transaction is in the  NON-EXISTING state

XA RECOVER

The XA RECOVER statement shows information about all transactions which are in the PREPARED state. It does not matter which connection created the transaction: if it has been PREPARED, it appears. But this does not mean that a connection can commit or rollback a transaction which was started by another connection. Note that transactions using a 1-phase commit are never in the PREPARED state, so they cannot be shown by XA RECOVER.

XA RECOVER produces four columns:

XA RECOVER;
+----------+--------------+--------------+------+
| formatID | gtrid_length | bqual_length | data |
+----------+--------------+--------------+------+
|        1 |            4 |            0 | test |
+----------+--------------+--------------+------+
MariaDB starting with 10.3.3

You can use XA RECOVER FORMAT='SQL' to get the data in a human readable form that can be directly copy-pasted into XA COMMIT or XA ROLLBACK. This is particularly useful for binary xid generated by some transaction coordinators.

formatID is the formatID part of xid.

data are the gtrid and bqual parts of xid, concatenated.

gtrid_length and bqual_length are the lengths of gtrid and bqual, respectevely.

Examples

2-phases commit:

XA START 'test';

INSERT INTO t VALUES (1,2);

XA END 'test';

XA PREPARE 'test';

XA COMMIT 'test';

1-phase commit:

XA START 'test';

INSERT INTO t VALUES (1,2);

XA END 'test';

XA COMMIT 'test' ONE PHASE;

Human-readable:

xa start '12\r34\t67\v78', 'abc\ndef', 3;

insert t1 values (40);

xa end '12\r34\t67\v78', 'abc\ndef', 3;

xa prepare '12\r34\t67\v78', 'abc\ndef', 3;

xa recover format='RAW';
+----------+--------------+--------------+--------------------+
| formatID | gtrid_length | bqual_length | data               |
+----------+--------------+--------------+--------------------+
34      67v78abc       11 |            7 | 12
def |
+----------+--------------+--------------+--------------------+

xa recover format='SQL';
+----------+--------------+--------------+-----------------------------------------------+
| formatID | gtrid_length | bqual_length | data                                          |
+----------+--------------+--------------+-----------------------------------------------+
|        3 |           11 |            7 | X'31320d3334093637763738',X'6162630a646566',3 |
+----------+--------------+--------------+-----------------------------------------------+

xa rollback X'31320d3334093637763738',X'6162630a646566',3;

Known Issues

MariaDB Galera Cluster

MariaDB Galera Cluster does not support XA transactions.

However, MariaDB Galera Cluster builds include a built-in plugin called wsrep. Prior to MariaDB 10.4.3, this plugin was internally considered an XA-capable storage engine. Consequently, these MariaDB Galera Cluster builds have multiple XA-capable storage engines by default, even if the only "real" storage engine that supports external XA transactions enabled on these builds by default is InnoDB. Therefore, when using one these builds MariaDB would be forced to use a transaction coordinator log by default, which could have performance implications.

See Transaction Coordinator Log Overview: MariaDB Galera Cluster for more information.

1.1.1.10 HELP Command

1.1.1.11 Comment Syntax

There are three supported comment styles in MariaDB:

  1. From a '#' to the end of a line:
    SELECT * FROM users; # This is a comment
  2. From a '-- ' to the end of a line. The space after the two dashes is required (as in MySQL).
    SELECT * FROM users; -- This is a comment
  3. C style comments from an opening '/*' to a closing '*/'. Comments of this form can span multiple lines:
    SELECT * FROM users; /* This is a
multi-line
comment */

Nested comments are possible in some situations, but they are not supported or recommended.

Executable Comments

As an aid to portability between different databases, MariaDB supports executable comments. These special comments allow you to embed SQL code which will not execute when run on other databases, but will execute when run on MariaDB.

MariaDB supports both MySQL's executable comment format, and a slightly modified version specific to MariaDB. This way, if you have SQL code that works on MySQL and MariaDB, but not other databases, you can wrap it in a MySQL executable comment, and if you have code that specifically takes advantage of features only available in MariaDB you can use the MariaDB specific format to hide the code from MySQL.

Executable Comment Syntax

MySQL and MariaDB executable comment syntax:

/*! MySQL or MariaDB-specific code */

Code that should be executed only starting from a specific MySQL or MariaDB version:

/*!##### MySQL or MariaDB-specific code */

The numbers, represented by '######' in the syntax examples above specify the specific the minimum versions of MySQL and MariaDB that should execute the comment. The first number is the major version, the second 2 numbers are the minor version and the last 2 is the patch level.

For example, if you want to embed some code that should only execute on MySQL or MariaDB starting from 5.1.0, you would do the following:

/*!50100 MySQL and MariaDB 5.1.0 (and above) code goes here. */

MariaDB-only executable comment syntax (starting from MariaDB 5.3.1):

/*M! MariaDB-specific code */
/*M!###### MariaDB-specific code */

MariaDB ignores MySQL-style executable comments that have a version number in the range 50700..99999. This is needed to skip features introduced in MySQL-5.7 that are not ported to MariaDB 10.x yet.

/*!50701 MariaDB-10.x ignores MySQL-5.7 specific code */

Note: comments which have a version number in the range 50700..99999 that use MariaDB-style executable comment syntax are still executed.

/*M!50701 MariaDB-10.x does not ignore this */

Statement delimiters cannot be used within executable comments.

Examples

In MySQL all the following will return 2: In MariaDB, the last 2 queries would return 3.

SELECT 2 /* +1 */;
SELECT 1 /*! +1 */;
SELECT 1 /*!50101 +1 */;
SELECT 2 /*M! +1 */;
SELECT 2 /*M!50301 +1 */;

The following executable statement will not work due to the delimiter inside the executable portion:

/*M!100100 select 1 ; */
ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that corresponds to your MariaDB server version for the right syntax to use near '' at line 1

Instead, the delimiter should be placed outside the executable portion:

/*M!100100 select 1 */;
+---+
| 1 |
+---+
| 1 |
+---+

1.1.1.12 Built-in Functions

1.1.2 SQL Language Structure

SQL language structure rules.

There are 3 related questions.

1.1.2.1 Identifier Names

Contents

  1. Unquoted
  2. Quoted
  3. Further Rules
  4. Quote Character
  5. Maximum Length
  6. Multiple Identifiers
  7. Examples

Databases, tables, indexes, columns, aliases, views, stored routines, triggers, events, variables, partitions, tablespaces, savepoints, labels, users, roles, are collectively known as identifiers, and have certain rules for naming.

Identifiers may be quoted using the backtick character - `. Quoting is optional for identifiers that don't contain special characters, or for identifiers that are not reserved words. If the ANSI_QUOTES SQL_MODE flag is set, double quotes (") can also be used to quote identifiers. If the MSSQL flag is set, square brackets ([ and ]) can be used for quoting.

Even when using reserved words as names, fully qualified names do not need to be quoted. For example, test.select has only one possible meaning, so it is correctly parsed even without quotes.

Unquoted

The following characters are valid, and allow identifiers to be unquoted:

  • ASCII: [0-9,a-z,A-Z$_] (numerals 0-9, basic Latin letters, both lowercase and uppercase, dollar sign, underscore)
  • Extended: U+0080 .. U+FFFF

Quoted

The following characters are valid, but identifiers using them must be quoted:

  • ASCII: U+0001 .. U+007F (full Unicode Basic Multilingual Plane (BMP) except for U+0000)
  • Extended: U+0080 .. U+FFFF
  • Identifier quotes can themselves be used as part of an identifier, as long as they are quoted.

Further Rules

There are a number of other rules for identifiers:

  • Identifiers are stored as Unicode (UTF-8)
  • Identifiers may or may not be case-sensitive. See Indentifier Case-sensitivity.
  • Database, table and column names can't end with space characters
  • Identifier names may begin with a numeral, but can't only contain numerals unless quoted.
  • An identifier starting with a numeral, followed by an 'e', may be parsed as a floating point number, and needs to be quoted.
  • Identifiers are not permitted to contain the ASCII NUL character (U+0000) and supplementary characters (U+10000 and higher).
  • Names such as 5e6, 9e are not prohibited, but it's strongly recommended not to use them, as they could lead to ambiguity in certain contexts, being treated as a number or expression.
  • User variables cannot be used as part of an identifier, or as an identifier in an SQL statement.

Quote Character

The regular quote character is the backtick character - `, but if the ANSI_QUOTES SQL_MODE option is specified, a regular double quote - " may be used as well.

The backtick character can be used as part of an identifier. In that case the identifier needs to be quoted. The quote character can be the backtick, but in that case, the backtick in the name must be escaped with another backtick.

Maximum Length

  • Databases, tables, columns, indexes, constraints, stored routines, triggers, events, views, tablespaces, servers and log file groups have a maximum length of 64 characters.
  • Compound statement labels have a maximum length of 16 characters
  • Aliases have a maximum length of 256 characters, except for column aliases in CREATE VIEW statements, which are checked against the maximum column length of 64 characters (not the maximum alias length of 256 characters).
  • Users have a maximum length of 80 characters.
  • Roles have a maximum length of 128 characters.
  • Multi-byte characters do not count extra towards towards the character limit.

Multiple Identifiers

MariaDB allows the column name to be used on its own if the reference will be unambiguous, or the table name to be used with the column name, or all three of the database, table and column names. A period is used to separate the identifiers, and the period can be surrounded by spaces.

Examples

Using the period to separate identifiers:

CREATE TABLE t1 (i int);

INSERT INTO t1(i) VALUES (10);

SELECT i FROM t1;
+------+
| i    |
+------+
|   10 |
+------+

SELECT t1.i FROM t1;
+------+
| i    |
+------+
|   10 |
+------+

SELECT test.t1.i FROM t1;
+------+
| i    |
+------+
|   10 |
+------+

The period can be separated by spaces:

SELECT test . t1 . i FROM t1;
+------+
| i    |
+------+
|   10 |
+------+

Resolving ambiguity:

CREATE TABLE t2 (i int);

SELECT i FROM t1 LEFT JOIN t2 ON t1.i=t2.i;
ERROR 1052 (23000): Column 'i' in field list is ambiguous

SELECT t1.i FROM t1 LEFT JOIN t2 ON t1.i=t2.i;
+------+
| i    |
+------+
|   10 |
+------+

Creating a table with characters that require quoting:

CREATE TABLE 123% (i int);
ERROR 1064 (42000): You have an error in your SQL syntax; 
  check the manual that corresponds to your MariaDB server version for the right syntax 
  to use near '123% (i int)' at line 1

CREATE TABLE `123%` (i int);
Query OK, 0 rows affected (0.85 sec)

CREATE TABLE `TABLE` (i int);
Query OK, 0 rows affected (0.36 sec)

Using double quotes as a quoting character:

CREATE TABLE "SELECT" (i int);
ERROR 1064 (42000): You have an error in your SQL syntax; 
  check the manual that corresponds to your MariaDB server version for the right syntax 
  to use near '"SELECT" (i int)' at line 1

SET sql_mode='ANSI_QUOTES';
Query OK, 0 rows affected (0.03 sec)

CREATE TABLE "SELECT" (i int);
Query OK, 0 rows affected (0.46 sec)

Using an identifier quote as part of an identifier name:

SHOW VARIABLES LIKE 'sql_mode';
+---------------+-------------+
| Variable_name | Value       |
+---------------+-------------+
| sql_mode      | ANSI_QUOTES |
+---------------+-------------+

CREATE TABLE "fg`d" (i int);
Query OK, 0 rows affected (0.34 sec)

Creating the table named * (Unicode number: U+002A) requires quoting.

CREATE TABLE `*` (a INT);

Floating point ambiguity:

CREATE TABLE 8984444cce5d (x INT);
Query OK, 0 rows affected (0.38 sec)

CREATE TABLE 8981e56cce5d (x INT);
ERROR 1064 (42000): You have an error in your SQL syntax; 
  check the manual that corresponds to your MariaDB server version for the right syntax 
  to use near '8981e56cce5d (x INT)' at line 1

CREATE TABLE `8981e56cce5d` (x INT);
Query OK, 0 rows affected (0.39 sec)

1.1.2.2 Identifier Case-sensitivity

Whether objects are case-sensitive or not is partly determined by the underlying operating system. Unix-based systems are case-sensitive, Windows is not, while Mac OS X is usually case-insensitive by default, but devices can be configured as case-sensitive using Disk Utility.

Database, table, table aliases and trigger names are affected by the systems case-sensitivity, while index, column, column aliases, stored routine and event names are never case sensitive.

Log file group name are case sensitive.

The lower_case_table_names server system variable plays a key role. It determines whether table names, aliases and database names are compared in a case-sensitive manner. If set to 0 (the default on Unix-based systems), table names and aliases and database names are compared in a case-sensitive manner. If set to 1 (the default on Windows), names are stored in lowercase and not compared in a case-sensitive manner. If set to 2 (the default on Mac OS X), names are stored as declared, but compared in lowercase.

It is thus possible to make Unix-based systems behave like Windows and ignore case-sensitivity, but the reverse is not true, as the underlying Windows filesystem can not support this.

Even on case-insensitive systems, you are required to use the same case consistently within the same statement. The following statement fails, as it refers to the table name in a different case.

SELECT * FROM a_table WHERE A_table.id>10;

For a full list of identifier naming rules, see Identifier Names.

Please note that lower_case_table_names is a database initialization parameter. This means that, along with innodb_page_size, this variable must be set before running mysql_install_db, and will not change the behavior of servers unless applied before the creation of core system databases.

1.1.2.3 Binary Literals

Binary literals can be written in one of the following formats: b'value', B'value' or 0bvalue, where value is a string composed by 0 and 1 digits.

Binary literals are interpreted as binary strings, and is convenient to represent VARBINARY, BINARY or BIT values.

To convert a binary literal into an integer, just add 0.

Examples

Printing the value as a binary string:

SELECT 0b1000001;
+-----------+
| 0b1000001 |
+-----------+
| A         |
+-----------+

Converting the same value into a number:

SELECT 0b1000001+0;
+-------------+
| 0b1000001+0 |
+-------------+
|          65 |
+-------------+

See ALso

1.1.2.4 Boolean Literals

In MariaDB, FALSE is a synonym of 0 and TRUE is a synonym of 1. These constants are case insensitive, so TRUE, True, and true are equivalent.

These terms are not synonyms of 0 and 1 when used with the IS operator. So, for example, 10 IS TRUE returns 1, while 10 = TRUE returns 0 (because 1 != 10).

The IS operator accepts a third constant exists: UNKNOWN. It is always a synonym of NULL.

TRUE and FALSE are reserved words, while UNKNOWN is not.

See Also

1.1.2.5 Date and Time Literals

Contents

  1. Standard syntaxes
  2. DATE literals
  3. DATETIME literals
  4. TIME literals
  5. 2-digit years
  6. Microseconds
  7. Date and time literals and the SQL_MODE
  8. See also

Standard syntaxes

MariaDB supports the SQL standard and ODBC syntaxes for DATE, TIME and TIMESTAMP literals.

SQL standard syntax:

  • DATE 'string'
  • TIME 'string'
  • TIMESTAMP 'string'

ODBC syntax:

  • {d 'string'}
  • {t 'string'}
  • {ts 'string'}

The timestamp literals are treated as DATETIME literals, because in MariaDB the range of DATETIME is closer to the TIMESTAMP range in the SQL standard.

string is a string in a proper format, as explained below.

DATE literals

A DATE string is a string in one of the following formats: 'YYYY-MM-DD' or 'YY-MM-DD'. Note that any punctuation character can be used as delimiter. All delimiters must consist of 1 character. Different delimiters can be used in the same string. Delimiters are optional (but if one delimiter is used, all delimiters must be used).

A DATE literal can also be an integer, in one of the following formats: YYYYMMDD or YYMMDD.

All the following DATE literals are valid, and they all represent the same value:

'19940101'
'940101'
'1994-01-01'
'94/01/01'
'1994-01/01'
'94:01!01'
19940101
940101

DATETIME literals

A DATETIME string is a string in one of the following formats: 'YYYY-MM-DD HH:MM:SS' or 'YY-MM-DD HH:MM:SS'. Note that any punctuation character can be used as delimiter for the date part and for the time part. All delimiters must consist of 1 character. Different delimiters can be used in the same string. The hours, minutes and seconds parts can consist of one character. For this reason, delimiters are mandatory for DATETIME literals.

The delimiter between the date part and the time part can be a T or any sequence of space characters (including tabs, new lines and carriage returns).

A DATETIME literal can also be a number, in one of the following formats: YYYYMMDDHHMMSS, YYMMDDHHMMSS, YYYYMMDD or YYMMDD. In this case, all the time subparts must consist of 2 digits.

All the following DATE literals are valid, and they all represent the same value:

'1994-01-01T12:30:03'
'1994/01/01\n\t 12+30+03'
'1994/01\\01\n\t 12+30-03'
'1994-01-01 12:30:3'

TIME literals

A TIME string is a string in one of the following formats: 'D HH:MM:SS', 'HH:MM:SS, 'D HH:MM', 'HH:MM', 'D HH', or 'SS'. D is a value from 0 to 34 which represents days. : is the only allowed delimiter for TIME literals. Delimiters are mandatory, with an exception: the 'HHMMSS' format is allowed. When delimiters are used, each part of the literal can consist of one character.

A TIME literal can also be a number in one of the following formats: HHMMSS, MMSS, or SS.

The following literals are equivalent:

'09:05:00'
'9:05:0'
'9:5:0'
'090500'

2-digit years

The year part in DATE and DATETIME literals is determined as follows:

  • 70 - 99 = 1970 - 1999
  • 00 - 69 = 2000 - 2069

Microseconds

DATETIME and TIME literals can have an optional microseconds part. For both string and numeric forms, it is expressed as a decimal part. Up to 6 decimal digits are allowed. Examples:

'12:30:00.123456'
123000.123456

See Microseconds in MariaDB for details.

Date and time literals and the SQL_MODE

Unless the SQL_MODE NO_ZERO_DATE flag is set, some special values are allowed: the '0000-00-00' DATE, the '00:00:00' TIME, and the 0000-00-00 00:00:00 DATETIME.

If the ALLOW_INVALID_DATES flag is set, the invalid dates (for example, 30th February) are allowed. If not, if the NO_ZERO_DATE is set, an error is produced; otherwise, a zero-date is returned.

Unless the NO_ZERO_IN_DATE flag is set, each subpart of a date or time value (years, hours...) can be set to 0.

See also

1.1.2.6 Hexadecimal Literals

Contents

  1. Examples
    1. Fun with Types
    2. Differences Between MariaDB and MySQL
  2. See Also

Hexadecimal literals can be written using any of the following syntaxes:

  • x'value'
  • X'value' (SQL standard)
  • 0xvalue (ODBC)

value is a sequence of hexadecimal digits (from 0 to 9 and from A to F). The case of the digits does not matter. With the first two syntaxes, value must consist of an even number of digits. With the last syntax, digits can be even, and they are treated as if they had an extra 0 at the beginning.

Normally, hexadecimal literals are interpreted as binary string, where each pair of digits represents a character. When used in a numeric context, they are interpreted as integers. (See the example below). In no case can a hexadecimal literal be a decimal number.

The first two syntaxes; X'value' and x'value, follow the SQL standard, and behave as a string in all contexts in MariaDB since MariaDB 10.0.3 and MariaDB 5.5.31 (fixing MDEV-4489). The latter syntax, 0xvalue, is a MySQL/MariaDB extension for hex hybrids and behaves as a string or as a number depending on context. MySQL treats all syntaxes the same, so there may be different results in MariaDB and MySQL (see below).

Examples

Representing the a character with the three syntaxes explained above:

SELECT x'61', X'61', 0x61;
+-------+-------+------+
| x'61' | X'61' | 0x61 |
+-------+-------+------+
| a     | a     | a    |
+-------+-------+------+

Hexadecimal literals in a numeric context:

SELECT 0 + 0xF, -0xF;
+---------+------+
| 0 + 0xF | -0xF |
+---------+------+
|      15 |  -15 |
+---------+------+

Fun with Types

CREATE TABLE t1 (a INT, b VARCHAR(10));
INSERT INTO t1 VALUES (0x31, 0x61),(COALESCE(0x31), COALESCE(0x61));

SELECT * FROM t1;
+------+------+
| a    | b    |
+------+------+
|   49 | a    |
|    1 | a    |
+------+------+

The reason for the differing results above is that when 0x31 is inserted directly to the column, it's treated as a number, while when 0x31 is passed to COALESCE(), it's treated as a string, because:

  • HEX values have a string data type by default.
  • COALESCE() has the same data type as the argument.

Differences Between MariaDB and MySQL

SELECT x'0a'+0;
+---------+
| x'0a'+0 |
+---------+
|       0 |
+---------+
1 row in set, 1 warning (0.00 sec)

Warning (Code 1292): Truncated incorrect DOUBLE value: '\x0A'

SELECT X'0a'+0;
+---------+
| X'0a'+0 |
+---------+
|       0 |
+---------+
1 row in set, 1 warning (0.00 sec)

Warning (Code 1292): Truncated incorrect DOUBLE value: '\x0A'

SELECT 0x0a+0;
+--------+
| 0x0a+0 |
+--------+
|     10 |
+--------+

In MySQL (up until at least MySQL 8.0.26):

SELECT x'0a'+0;
+---------+
| x'0a'+0 |
+---------+
|      10 |
+---------+

SELECT X'0a'+0;
+---------+
| X'0a'+0 |
+---------+
|      10 |
+---------+

SELECT 0x0a+0;
+--------+
| 0x0a+0 |
+--------+
|     10 |
+--------+

See Also

1.1.2.7 Identifier Qualifiers

Contents

  1. See Also

Qualifiers are used within SQL statements to reference data structures, such as databases, tables, or columns. For example, typically a SELECT query contains references to some columns and at least one table.

Qualifiers can be composed by one or more identifiers, where the initial parts affect the context within which the final identifier is interpreted:

  • For a database, only the database identifier needs to be specified.
  • For objects which are contained in a database (like tables, views, functions, etc) the database identifier can be specified. If no database is specified, the current database is assumed (see USE and DATABASE() for more details). If there is no default database and no database is specified, an error is issued.
  • For column names, the table and the database are generally obvious from the context of the statement. It is however possible to specify the table identifier, or the database identifier plus the table identifier.
  • An identifier is fully-qualified if it contains all possible qualifiers, for example, the following column is fully qualified: db_name.tbl_name.col_name.

If a qualifier is composed by more than one identifier, a dot (.) must be used as a separator. All identifiers can be quoted individually. Extra spacing (including new lines and tabs) is allowed.

All the following examples are valid:

  • db_name.tbl_name.col_name
  • tbl_name
  • `db_name`.`tbl_name`.`col_name`
  • `db_name` . `tbl_name`
  • db_name. tbl_name

If a table identifier is prefixed with a dot (.), the default database is assumed. This syntax is supported for ODBC compliance, but has no practical effect on MariaDB. These qualifiers are equivalent:

  • tbl_name
  • . tbl_name
  • .`tbl_name`
  • . `tbl_name`

For DML statements, it is possible to specify a list of the partitions using the PARTITION clause. See Partition Pruning and Selection for details.

See Also

1.1.2.8 Identifier to File Name Mapping

Some identifiers map to a file name on the filesystem. Databases each have their own directory, while, depending on the storage engine, table names and index names may map to a file name.

Not all characters that are allowed in table names can be used in file names. Every filesystem has its own rules of what characters can be used in file names. To let the user create tables using all characters allowed in the SQL Standard and to not depend on whatever particular filesystem a particular database resides, MariaDB encodes "potentially unsafe" characters in the table name to derive the corresponding file name.

This is implemented using a special character set. MariaDB converts a table name to the "filename" character set to get the file name for this table. And it converts the file name from the "filename" character set to, for example, utf8 to get the table name for this file name.

The conversion rules are as follows: if the identifier is made up only of basic Latin numbers, letters and/or the underscore character, the encoding matches the name (see however Identifier Case Sensitivity). Otherwise they are encoded according to the following table:

Code RangePatternNumberUsedUnusedBlocks
00C0..017F[@][0..4][g..z]5*20= 100973Latin-1 Supplement + Latin Extended-A
0370..03FF[@][5..9][g..z]5*20= 1008812Greek and Coptic
0400..052F[@][g..z][0..6]20*7= 1401373Cyrillic + Cyrillic Supplement
0530..058F[@][g..z][7..8]20*2= 40382Armenian
2160..217F[@][g..z][9]20*1= 20164Number Forms
0180..02AF[@][g..z][a..k]20*11=22020317Latin Extended-B + IPA Extensions
1E00..1EFF[@][g..z][l..r]20*7= 1401364Latin Extended Additional
1F00..1FFF[@][g..z][s..z]20*8= 16014416Greek Extended
.... ....[@][a..f][g..z]6*20= 1200120RESERVED
24B6..24E9[@][@][a..z]26260Enclosed Alphanumerics
FF21..FF5A[@][a..z][@]26260Halfwidth and Fullwidth forms

Code Range values are UCS-2.

All of this encoding happens transparently at the filesystem level with one exception. Until MySQL 5.1.6, an old encoding was used. Identifiers created in a version before MySQL 5.1.6, and which haven't been updated to the new encoding, the server prefixes mysql50 to their name.

Examples

Find the file name for a table with a non-Latin1 name:

select cast(convert("this_is_таблица" USING filename) as binary);
+------------------------------------------------------------------+
| cast(convert("this_is_таблица" USING filename) as binary)        |
+------------------------------------------------------------------+
| this_is_@y0@g0@h0@r0@o0@i1@g0                                    |
+------------------------------------------------------------------+

Find the table name for a file name:

select convert(_filename "this_is_@y0@g0@h0@r0@o0@i1@g0" USING utf8);
+---------------------------------------------------------------+
| convert(_filename "this_is_@y0@g0@h0@r0@o0@i1@g0" USING utf8) |
+---------------------------------------------------------------+
| this_is_таблица                                               |
+---------------------------------------------------------------+

An old table created before MySQL 5.1.6, with the old encoding:

SHOW TABLES;
+--------------------+
| Tables_in_test     |
+--------------------+
| #mysql50#table@1   |
+--------------------+

The prefix needs to be supplied to reference this table:

SHOW COLUMNS FROM `table@1`;
ERROR 1146 (42S02): Table 'test.table@1' doesn't exist

SHOW COLUMNS FROM `#mysql50#table@1`;
+-------+---------+------+-----+---------+-------+
| Field | Type    | Null | Key | Default | Extra |
+-------+---------+------+-----+---------+-------+
| i     | int(11) | YES  |     | NULL    |       |
+-------+---------+------+-----+---------+-------+

1.1.2.9 MariaDB Error Codes

MariaDB shares error codes with MySQL, as well as adding a number of new error codes specific to MariaDB.

An example of an error code is as follows:

SELECT * FROM x;
ERROR 1046 (3D000): No database selected

Contents

  1. Shared MariaDB/MySQL error codes
  2. MariaDB-specific error codes

There are three pieces of information returned in an error:

  • A numeric error code, in this case 1046. Error codes from 1900 and up are specific to MariaDB, while error codes from 1000 to 1800 are shared by MySQL and MariaDB.
  • An SQLSTATE value, consisting of five characters, in this case 3D000. These codes are standard to ODBC and ANSI SQL. When MariaDB cannot allocate a standard SQLSTATE code, a generic HY000, or general error, is used.
  • A string describing the error, in this case No database selected.

New error codes are being continually being added as new features are added. For a definitive list, see the file sql/share/errmsg-utf8.txt, as well as include/mysqld_error.h in the build directory, generated by the comp_err tool. Also, the perror tool can be used to get the error message which is associated with a given error code.

Shared MariaDB/MySQL error codes

Error CodeSQLSTATEErrorDescription
1000HY000ER_HASHCHKhashchk
1001HY000ER_NISAMCHKisamchk
1002HY000ER_NONO
1003HY000ER_YESYES
1004HY000ER_CANT_CREATE_FILECan't create file '%s' (errno: %d)
1005HY000ER_CANT_CREATE_TABLECan't create table '%s' (errno: %d)
1006HY000ER_CANT_CREATE_DBCan't create database '%s' (errno: %d
1007HY000ER_DB_CREATE_EXISTSCan't create database '%s'; database exists
1008HY000ER_DB_DROP_EXISTSCan't drop database '%s'; database doesn't exist
1009HY000ER_DB_DROP_DELETEError dropping database (can't delete '%s', errno: %d)
1010HY000ER_DB_DROP_RMDIRError dropping database (can't rmdir '%s', errno: %d)
1011HY000ER_CANT_DELETE_FILEError on delete of '%s' (errno: %d)
1012HY000ER_CANT_FIND_SYSTEM_RECCan't read record in system table
1013HY000ER_CANT_GET_STATCan't get status of '%s' (errno: %d)
1014HY000ER_CANT_GET_WDCan't get working directory (errno: %d)
1015HY000ER_CANT_LOCKCan't lock file (errno: %d)
1016HY000ER_CANT_OPEN_FILECan't open file: '%s' (errno: %d)
1017HY000ER_FILE_NOT_FOUNDCan't find file: '%s' (errno: %d)
1018HY000ER_CANT_READ_DIRCan't read dir of '%s' (errno: %d)
1019HY000ER_CANT_SET_WDCan't change dir to '%s' (errno: %d)
1020HY000ER_CHECKREADRecord has changed since last read in table '%s'
1021HY000ER_DISK_FULLDisk full (%s); waiting for someone to free some space...
102223000ER_DUP_KEYCan't write; duplicate key in table '%s'
1023HY000ER_ERROR_ON_CLOSEError on close of '%s' (errno: %d)
1024HY000ER_ERROR_ON_READError reading file '%s' (errno: %d)
1025HY000ER_ERROR_ON_RENAMEError on rename of '%s' to '%s' (errno: %d)
1026HY000ER_ERROR_ON_WRITEError writing file '%s' (errno: %d)
1027HY000ER_FILE_USED'%s' is locked against change
1028HY000ER_FILSORT_ABORTSort aborted
1029HY000ER_FORM_NOT_FOUNDView '%s' doesn't exist for '%s'
1030HY000ER_GET_ERRNGot error %d from storage engine
1031HY000ER_ILLEGAL_HATable storage engine for '%s' doesn't have this option
1032HY000ER_KEY_NOT_FOUNDCan't find record in '%s'
1033HY000ER_NOT_FORM_FILEIncorrect information in file: '%s'
1034HY000ER_NOT_KEYFILEIncorrect key file for table '%s'; try to repair it
1035HY000ER_OLD_KEYFILEOld key file for table '%s'; repair it!
1036HY000ER_OPEN_AS_READONLYTable '%s' is read only
1037HY001ER_OUTOFMEMORYOut of memory; restart server and try again (needed %d bytes)
1038HY001ER_OUT_OF_SORTMEMORYOut of sort memory, consider increasing server sort buffer size
1039HY000ER_UNEXPECTED_EOFUnexpected EOF found when reading file '%s' (Errno: %d)
104008004ER_CON_COUNT_ERRORToo many connections
1041HY000ER_OUT_OF_RESOURCESOut of memory; check if mysqld or some other process uses all available memory; if not, you may have to use 'ulimit' to allow mysqld to use more memory or you can add more swap space
104208S01ER_BAD_HOST_ERRORCan't get hostname for your address
104308S01ER_HANDSHAKE_ERRORBad handshake
104442000ER_DBACCESS_DENIED_ERRORAccess denied for user '%s'@'%s' to database '%s'
104528000ER_ACCESS_DENIED_ERRORAccess denied for user '%s'@'%s' (using password: %s)
10463D000ER_NO_DB_ERRORNo database selected
104708S01ER_UNKNOWN_COM_ERRORUnknown command
104823000ER_BAD_NULL_ERRORColumn '%s' cannot be null
104942000ER_BAD_DB_ERRORUnknown database '%s'
105042S01ER_TABLE_EXISTS_ERRORTable '%s' already exists
105142S02ER_BAD_TABLE_ERRORUnknown table '%s'
105223000ER_NON_UNIQ_ERRORColumn '%s' in %s is ambiguous
105308S01ER_SERVER_SHUTDOWNServer shutdown in progress
105442S22ER_BAD_FIELD_ERRORUnknown column '%s' in '%s'
105542000ER_WRONG_FIELD_WITH_GROUP'%s' isn't in GROUP BY
105642000ER_WRONG_GROUP_FIELDCan't group on '%s'
105742000ER_WRONG_SUM_SELECTStatement has sum functions and columns in same statement
105821S01ER_WRONG_VALUE_COUNTColumn count doesn't match value count
105942000ER_TOO_LONG_IDENTIdentifier name '%s' is too long
106042S21ER_DUP_FIELDNAMEDuplicate column name '%s'
106142000ER_DUP_KEYNAMEDuplicate key name '%s'
106223000ER_DUP_ENTRYDuplicate entry '%s' for key %d
106342000ER_WRONG_FIELD_SPECIncorrect column specifier for column '%s'
106442000ER_PARSE_ERROR%s near '%s' at line %d
106542000ER_EMPTY_QUERYQuery was empty
106642000ER_NONUNIQ_TABLENot unique table/alias: '%s'
106742000ER_INVALID_DEFAULTInvalid default value for '%s'
106842000ER_MULTIPLE_PRI_KEYMultiple primary key defined
106942000ER_TOO_MANY_KEYSToo many keys specified; max %d keys allowed
107042000ER_TOO_MANY_KEY_PARTSToo many key parts specified; max %d parts allowed
107142000ER_TOO_LONG_KEYSpecified key was too long; max key length is %d bytes
107242000ER_KEY_COLUMN_DOES_NOT_EXITSKey column '%s' doesn't exist in table
107342000ER_BLOB_USED_AS_KEYBLOB column '%s' can't be used in key specification with the used table type
107442000ER_TOO_BIG_FIELDLENGTHColumn length too big for column '%s' (max = %lu); use BLOB or TEXT instead
107542000ER_WRONG_AUTO_KEYIncorrect table definition; there can be only one auto column and it must be defined as a key
1076HY000ER_READY%s: ready for connections. Version: '%s' socket: '%s' port: %d
1077HY000ER_NORMAL_SHUTDOWN%s: Normal shutdown
1078HY000ER_GOT_SIGNAL%s: Got signal %d. Aborting!
1079HY000ER_SHUTDOWN_COMPLETE%s: Shutdown complete
108008S01ER_FORCING_CLOSE%s: Forcing close of thread %ld user: '%s'
108108S01ER_IPSOCK_ERRORCan't create IP socket
108242S12ER_NO_SUCH_INDEXTable '%s' has no index like the one used in CREATE INDEX; recreate the table
108342000ER_WRONG_FIELD_TERMINATORSField separator argument is not what is expected; check the manual
108442000ER_BLOBS_AND_NO_TERMINATEDYou can't use fixed rowlength with BLOBs; please use 'fields terminated by'
1085HY000ER_TEXTFILE_NOT_READABLEThe file '%s' must be in the database directory or be readable by all
1086HY000ER_FILE_EXISTS_ERRORFile '%s' already exists
1087HY000ER_LOAD_INFRecords: %ld Deleted: %ld Skipped: %ld Warnings: %ld
1088HY000ER_ALTER_INFRecords: %ld Duplicates: %ld
1089HY000ER_WRONG_SUB_KEYIncorrect prefix key; the used key part isn't a string, the used length is longer than the key part, or the storage engine doesn't support unique prefix keys
109042000ER_CANT_REMOVE_ALL_FIELDSYou can't delete all columns with ALTER TABLE; use DROP TABLE instead
109142000ER_CANT_DROP_FIELD_OR_KEYCan't DROP '%s'; check that column/key exists
1092HY000ER_INSERT_INFRecords: %ld Duplicates: %ld Warnings: %ld
1093HY000ER_UPDATE_TABLE_USEDYou can't specify target table '%s' for update in FROM clause
1094HY000ER_NO_SUCH_THREADUnknown thread id: %lu
1095HY000ER_KILL_DENIED_ERRORYou are not owner of thread %lu
1096HY000ER_NO_TABLES_USEDNo tables used
1097HY000ER_TOO_BIG_SETToo many strings for column %s and SET
1098HY000ER_NO_UNIQUE_LOGFILECan't generate a unique log-filename %s.(1-999)
1099HY000ER_TABLE_NOT_LOCKED_FOR_WRITETable '%s' was locked with a READ lock and can't be updated
Error CodeSQLSTATEErrorDescription
1100HY000ER_TABLE_NOT_LOCKEDTable '%s' was not locked with LOCK TABLES
1101ER_UNUSED_17You should never see it
110242000ER_WRONG_DB_NAMEIncorrect database name '%s'
110342000ER_WRONG_TABLE_NAMEIncorrect table name '%s'
110442000ER_TOO_BIG_SELECTThe SELECT would examine more than MAX_JOIN_SIZE rows; check your WHERE and use SET SQL_BIG_SELECTS=1 or SET MAX_JOIN_SIZE=# if the SELECT is okay
1105HY000ER_UNKNOWN_ERRORUnknown error
110642000ER_UNKNOWN_PROCEDUREUnknown procedure '%s'
110742000ER_WRONG_PARAMCOUNT_TO_PROCEDUREIncorrect parameter count to procedure '%s'
1108HY000ER_WRONG_PARAMETERS_TO_PROCEDUREIncorrect parameters to procedure '%s'
110942S02ER_UNKNOWN_TABLEUnknown table '%s' in %s
111042000ER_FIELD_SPECIFIED_TWICEColumn '%s' specified twice
1111HY000ER_INVALID_GROUP_FUNC_USEInvalid use of group function
111242000ER_UNSUPPORTED_EXTENSIONTable '%s' uses an extension that doesn't exist in this MariaDB version
111342000ER_TABLE_MUST_HAVE_COLUMNSA table must have at least 1 column
1114HY000ER_RECORD_FILE_FULLThe table '%s' is full
111542000ER_UNKNOWN_CHARACTER_SETUnknown character set: '%s'
1116HY000ER_TOO_MANY_TABLESToo many tables; MariaDB can only use %d tables in a join
1117HY000ER_TOO_MANY_FIELDSToo many columns
111842000ER_TOO_BIG_ROWSIZERow size too large. The maximum row size for the used table type, not counting BLOBs, is %ld. You have to change some columns to TEXT or BLOBs
1119HY000ER_STACK_OVERRUNThread stack overrun: Used: %ld of a %ld stack. Use 'mysqld --thread_stack=#' to specify a bigger stack if needed
112042000ER_WRONG_OUTER_JOINCross dependency found in OUTER JOIN; examine your ON conditions
112142000ER_NULL_COLUMN_IN_INDEXTable handler doesn't support NULL in given index. Please change column '%s' to be NOT NULL or use another handler
1122HY000ER_CANT_FIND_UDFCan't load function '%s'
1123HY000ER_CANT_INITIALIZE_UDFCan't initialize function '%s'; %s
1124HY000ER_UDF_NO_PATHSNo paths allowed for shared library
1125HY000ER_UDF_EXISTSFunction '%s' already exists
1126HY000ER_CANT_OPEN_LIBRARYCan't open shared library '%s' (Errno: %d %s)
1127HY000ER_CANT_FIND_DL_ENTRYCan't find symbol '%s' in library
1128HY000ER_FUNCTION_NOT_DEFINEDFunction '%s' is not defined
1129HY000ER_HOST_IS_BLOCKEDHost '%s' is blocked because of many connection errors; unblock with 'mysqladmin flush-hosts'
1130HY000ER_HOST_NOT_PRIVILEGEDHost '%s' is not allowed to connect to this MariaDB server
113142000ER_PASSWORD_ANONYMOUS_USERYou are using MariaDB as an anonymous user and anonymous users are not allowed to change passwords
113242000ER_PASSWORD_NOT_ALLOWEDYou must have privileges to update tables in the mysql database to be able to change passwords for others
113342000ER_PASSWORD_NO_MATCHCan't find any matching row in the user table
1134HY000ER_UPDATE_INFRows matched: %ld Changed: %ld Warnings: %ld
1135HY000ER_CANT_CREATE_THREADCan't create a new thread (Errno %d); if you are not out of available memory, you can consult the manual for a possible OS-dependent bug
113621S01ER_WRONG_VALUE_COUNT_ON_ROWColumn count doesn't match value count at row %ld
1137HY000ER_CANT_REOPEN_TABLECan't reopen table: '%s'
113822004ER_INVALID_USE_OF_NULLInvalid use of NULL value
113942000ER_REGEXP_ERRORGot error '%s' from regexp
114042000ER_MIX_OF_GROUP_FUNC_AND_FIELDSMixing of GROUP columns (MIN(),MAX(),COUNT(),...) with no GROUP columns is illegal if there is no GROUP BY clause
114142000ER_NONEXISTING_GRANTThere is no such grant defined for user '%s' on host '%s'
114242000ER_TABLEACCESS_DENIED_ERROR%s command denied to user '%s'@'%s' for table '%s'
114342000ER_COLUMNACCESS_DENIED_ERROR%s command denied to user '%s'@'%s' for column '%s' in table '%s'
114442000ER_ILLEGAL_GRANT_FOR_TABLEIllegal GRANT/REVOKE command; please consult the manual to see which privileges can be used
114542000ER_GRANT_WRONG_HOST_OR_USERThe host or user argument to GRANT is too long
114642S02ER_NO_SUCH_TABLETable '%s.%s' doesn't exist
114742000ER_NONEXISTING_TABLE_GRANTThere is no such grant defined for user '%s' on host '%s' on table '%s'
114842000ER_NOT_ALLOWED_COMMANDThe used command is not allowed with this MariaDB version
114942000ER_SYNTAX_ERRORYou have an error in your SQL syntax; check the manual that corresponds to your MariaDB server version for the right syntax to use
1150HY000ER_DELAYED_CANT_CHANGE_LOCKDelayed insert thread couldn't get requested lock for table %s
1151HY000ER_TOO_MANY_DELAYED_THREADSToo many delayed threads in use
115208S01ER_ABORTING_CONNECTIONAborted connection %ld to db: '%s' user: '%s' (%s)
115308S01ER_NET_PACKET_TOO_LARGEGot a packet bigger than 'max_allowed_packet' bytes
115408S01ER_NET_READ_ERROR_FROM_PIPEGot a read error from the connection pipe
115508S01ER_NET_FCNTL_ERRORGot an error from fcntl()
115608S01ER_NET_PACKETS_OUT_OF_ORDERGot packets out of order
115708S01ER_NET_UNCOMPRESS_ERRORCouldn't uncompress communication packet
115808S01ER_NET_READ_ERRORGot an error reading communication packets
115908S01ER_NET_READ_INTERRUPTEDGot timeout reading communication packets
116008S01ER_NET_ERROR_ON_WRITEGot an error writing communication packets
116108S01ER_NET_WRITE_INTERRUPTEDGot timeout writing communication packets
116242000ER_TOO_LONG_STRINGResult string is longer than 'max_allowed_packet' bytes
116342000ER_TABLE_CANT_HANDLE_BLOBThe used table type doesn't support BLOB/TEXT columns
116442000ER_TABLE_CANT_HANDLE_AUTO_INCREMENTThe used table type doesn't support AUTO_INCREMENT columns
1165HY000ER_DELAYED_INSERT_TABLE_LOCKEDINSERT DELAYED can't be used with table '%s' because it is locked with LOCK TABLES
116642000ER_WRONG_COLUMN_NAMEIncorrect column name '%s'
116742000ER_WRONG_KEY_COLUMNThe used storage engine can't index column '%s'
1168HY000ER_WRONG_MRG_TABLEUnable to open underlying table which is differently defined or of non-MyISAM type or doesn't exist
116923000ER_DUP_UNIQUECan't write, because of unique constraint, to table '%s'
117042000ER_BLOB_KEY_WITHOUT_LENGTHBLOB/TEXT column '%s' used in key specification without a key length
117142000ER_PRIMARY_CANT_HAVE_NULLAll parts of a PRIMARY KEY must be NOT NULL; if you need NULL in a key, use UNIQUE instead
117242000ER_TOO_MANY_ROWSResult consisted of more than one row
117342000ER_REQUIRES_PRIMARY_KEYThis table type requires a primary key
1174HY000ER_NO_RAID_COMPILEDThis version of MariaDB is not compiled with RAID support
1175HY000ER_UPDATE_WITHOUT_KEY_IN_SAFE_MODEYou are using safe update mode and you tried to update a table without a WHERE that uses a KEY column
117642000ER_KEY_DOES_NOT_EXITSKey '%s' doesn't exist in table '%s'
117742000ER_CHECK_NO_SUCH_TABLECan't open table
117842000ER_CHECK_NOT_IMPLEMENTEDThe storage engine for the table doesn't support %s
117925000ER_CANT_DO_THIS_DURING_AN_TRANSACTIONYou are not allowed to execute this command in a transaction
1180HY000ER_ERROR_DURING_COMMITGot error %d during COMMIT
1181HY000ER_ERROR_DURING_ROLLBACKGot error %d during ROLLBACK
1182HY000ER_ERROR_DURING_FLUSH_LOGSGot error %d during FLUSH_LOGS
1183HY000ER_ERROR_DURING_CHECKPOINTGot error %d during CHECKPOINT
118408S01ER_NEW_ABORTING_CONNECTIONAborted connection %ld to db: '%s' user: '%s' host: '%s' (%s)
1185ER_UNUSED_10You should never see it
1186HY000ER_FLUSH_MASTER_BINLOG_CLOSEDBinlog closed, cannot RESET MASTER
1187HY000ER_INDEX_REBUILDFailed rebuilding the index of dumped table '%s'
1188HY000ER_MASTERError from master: '%s'
118908S01ER_MASTER_NET_READNet error reading from master
119008S01ER_MASTER_NET_WRITENet error writing to master
1191HY000ER_FT_MATCHING_KEY_NOT_FOUNDCan't find FULLTEXT index matching the column list
1192HY000ER_LOCK_OR_ACTIVE_TRANSACTIONCan't execute the given command because you have active locked tables or an active transaction
1193HY000ER_UNKNOWN_SYSTEM_VARIABLEUnknown system variable '%s'
1194HY000ER_CRASHED_ON_USAGETable '%s' is marked as crashed and should be repaired
1195HY000ER_CRASHED_ON_REPAIRTable '%s' is marked as crashed and last (automatic?) repair failed
1196HY000ER_WARNING_NOT_COMPLETE_ROLLBACKSome non-transactional changed tables couldn't be rolled back
1197HY000ER_TRANS_CACHE_FULLMulti-statement transaction required more than 'max_binlog_cache_size' bytes of storage; increase this mysqld variable and try again
1198HY000ER_SLAVE_MUST_STOPThis operation cannot be performed with a running slave; run STOP SLAVE first
1199HY000ER_SLAVE_NOT_RUNNINGThis operation requires a running slave; configure slave and do START SLAVE
Error CodeSQLSTATEErrorDescription
1200HY000ER_BAD_SLAVEThe server is not configured as slave; fix in config file or with CHANGE MASTER TO
1201HY000ER_MASTER_INFCould not initialize master info structure; more error messages can be found in the MariaDB error log
1202HY000ER_SLAVE_THREADCould not create slave thread; check system resources
120342000ER_TOO_MANY_USER_CONNECTIONSUser %s already has more than 'max_user_connections' active connections
1204HY000ER_SET_CONSTANTS_ONLYYou may only use constant expressions with SET
1205HY000ER_LOCK_WAIT_TIMEOUTLock wait timeout exceeded; try restarting transaction
1206HY000ER_LOCK_TABLE_FULLThe total number of locks exceeds the lock table size
120725000ER_READ_ONLY_TRANSACTIONUpdate locks cannot be acquired during a READ UNCOMMITTED transaction
1208HY000ER_DROP_DB_WITH_READ_LOCKDROP DATABASE not allowed while thread is holding global read lock
1209HY000ER_CREATE_DB_WITH_READ_LOCKCREATE DATABASE not allowed while thread is holding global read lock
1210HY000ER_WRONG_ARGUMENTSIncorrect arguments to %s
121142000ER_NO_PERMISSION_TO_CREATE_USER'%s'@'%s' is not allowed to create new users
1212HY000ER_UNION_TABLES_IN_DIFFERENT_DIRIncorrect table definition; all MERGE tables must be in the same database
121340001ER_LOCK_DEADLOCKDeadlock found when trying to get lock; try restarting transaction
1214HY000ER_TABLE_CANT_HANDLE_FTThe used table type doesn't support FULLTEXT indexes
1215HY000ER_CANNOT_ADD_FOREIGNCannot add foreign key constraint
121623000ER_NO_REFERENCED_ROWCannot add or update a child row: a foreign key constraint fails
121723000ER_ROW_IS_REFERENCEDCannot delete or update a parent row: a foreign key constraint fails
121808S01ER_CONNECT_TO_MASTERError connecting to master: %s
1219HY000ER_QUERY_ON_MASTERError running query on master: %s
1220HY000ER_ERROR_WHEN_EXECUTING_COMMANDError when executing command %s: %s
1221HY000ER_WRONG_USAGEIncorrect usage of %s and %s
122221000ER_WRONG_NUMBER_OF_COLUMNS_IN_SELECTThe used SELECT statements have a different number of columns
1223HY000ER_CANT_UPDATE_WITH_READLOCKCan't execute the query because you have a conflicting read lock
1224HY000ER_MIXING_NOT_ALLOWEDMixing of transactional and non-transactional tables is disabled
1225HY000ER_DUP_ARGUMENTOption '%s' used twice in statement
122642000ER_USER_LIMIT_REACHEDUser '%s' has exceeded the '%s' resource (current value: %ld)
122742000ER_SPECIFIC_ACCESS_DENIED_ERRORAccess denied; you need (at least one of) the %s privilege(s) for this operation
1228HY000ER_LOCAL_VARIABLEVariable '%s' is a SESSION variable and can't be used with SET GLOBAL
1229HY000ER_GLOBAL_VARIABLEVariable '%s' is a GLOBAL variable and should be set with SET GLOBAL
123042000ER_NO_DEFAULTVariable '%s' doesn't have a default value
123142000ER_WRONG_VALUE_FOR_VARVariable '%s' can't be set to the value of '%s'
123242000ER_WRONG_TYPE_FOR_VARIncorrect argument type to variable '%s'
1233HY000ER_VAR_CANT_BE_READVariable '%s' can only be set, not read
123442000ER_CANT_USE_OPTION_HEREIncorrect usage/placement of '%s'
123542000ER_NOT_SUPPORTED_YETThis version of MariaDB doesn't yet support '%s'
1236HY000ER_MASTER_FATAL_ERROR_READING_BINLOGGot fatal error %d from master when reading data from binary log: '%s'
1237HY000ER_SLAVE_IGNORED_TABLESlave SQL thread ignored the query because of replicate-*-table rules
1238HY000ER_INCORRECT_GLOBAL_LOCAL_VARVariable '%s' is a %s variable
123942000ER_WRONG_FK_DEFIncorrect foreign key definition for '%s': %s
1240HY000ER_KEY_REF_DO_NOT_MATCH_TABLE_REFKey reference and table reference don't match
124121000ER_OPERAND_COLUMNSOperand should contain %d column(s)
124221000ER_SUBQUERY_NO_1_ROWSubquery returns more than 1 row
1243HY000ER_UNKNOWN_STMT_HANDLERUnknown prepared statement handler (%.*s) given to %s
1244HY000ER_CORRUPT_HELP_DBHelp database is corrupt or does not exist
1245HY000ER_CYCLIC_REFERENCECyclic reference on subqueries
1246HY000ER_AUTO_CONVERTConverting column '%s' from %s to %s
124742S22ER_ILLEGAL_REFERENCEReference '%s' not supported (%s)
124842000ER_DERIVED_MUST_HAVE_ALIASEvery derived table must have its own alias
124901000ER_SELECT_REDUCEDSelect %u was reduced during optimization
125042000ER_TABLENAME_NOT_ALLOWED_HERETable '%s' from one of the SELECTs cannot be used in %s
125108004ER_NOT_SUPPORTED_AUTH_MODEClient does not support authentication protocol requested by server; consider upgrading MariaDB client
125242000ER_SPATIAL_CANT_HAVE_NULLAll parts of a SPATIAL index must be NOT NULL
125342000ER_COLLATION_CHARSET_MISMATCHCOLLATION '%s' is not valid for CHARACTER SET '%s'
1254HY000ER_SLAVE_WAS_RUNNINGSlave is already running
1255HY000ER_SLAVE_WAS_NOT_RUNNINGSlave already has been stopped
1256HY000ER_TOO_BIG_FOR_UNCOMPRESSUncompressed data size too large; the maximum size is %d (probably, length of uncompressed data was corrupted)
1257HY000ER_ZLIB_Z_MEM_ERRORZLIB: Not enough memory
1258HY000ER_ZLIB_Z_BUF_ERRORZLIB: Not enough room in the output buffer (probably, length of uncompressed data was corrupted)
1259HY000ER_ZLIB_Z_DATA_ERRORZLIB: Input data corrupted
1260HY000ER_CUT_VALUE_GROUP_CONCATRow %u was cut by GROUP_CONCAT()
126101000ER_WARN_TOO_FEW_RECORDSRow %ld doesn't contain data for all columns
126201000ER_WARN_TOO_MANY_RECORDSRow %ld was truncated; it contained more data than there were input columns
126322004ER_WARN_NULL_TO_NOTNULLColumn set to default value; NULL supplied to NOT NULL column '%s' at row %ld
126422003ER_WARN_DATA_OUT_OF_RANGEOut of range value for column '%s' at row %ld
126501000WARN_DATA_TRUNCATEDData truncated for column '%s' at row %ld
1266HY000ER_WARN_USING_OTHER_HANDLERUsing storage engine %s for table '%s'
1267HY000ER_CANT_AGGREGATE_2COLLATIONSIllegal mix of collations (%s,%s) and (%s,%s) for operation '%s'
1268HY000ER_DROP_USERCannot drop one or more of the requested users
1269HY000ER_REVOKE_GRANTSCan't revoke all privileges for one or more of the requested users
1270HY000ER_CANT_AGGREGATE_3COLLATIONSIllegal mix of collations (%s,%s), (%s,%s), (%s,%s) for operation '%s'
1271HY000ER_CANT_AGGREGATE_NCOLLATIONSIllegal mix of collations for operation '%s'
1272HY000ER_VARIABLE_IS_NOT_STRUCTVariable '%s' is not a variable component (can't be used as XXXX.variable_name)
1273HY000ER_UNKNOWN_COLLATIONUnknown collation: '%s'
1274HY000ER_SLAVE_IGNORED_SSL_PARAMSSSL parameters in CHANGE MASTER are ignored because this MariaDB slave was compiled without SSL support; they can be used later if MariaDB slave with SSL is started
1275HY000ER_SERVER_IS_IN_SECURE_AUTH_MODEServer is running in --secure-auth mode, but '%s'@'%s' has a password in the old format; please change the password to the new format
1276HY000ER_WARN_FIELD_RESOLVEDField or reference '%s%s%s%s%s' of SELECT #%d was resolved in SELECT #%d
1277HY000ER_BAD_SLAVE_UNTIL_CONDIncorrect parameter or combination of parameters for START SLAVE UNTIL
1278HY000ER_MISSING_SKIP_SLAVEIt is recommended to use --skip-slave-start when doing step-by-step replication with START SLAVE UNTIL; otherwise, you will get problems if you get an unexpected slave's mysqld restart
1279HY000ER_UNTIL_COND_IGNOREDSQL thread is not to be started so UNTIL options are ignored
128042000ER_WRONG_NAME_FOR_INDEXIncorrect index name '%s'
128142000ER_WRONG_NAME_FOR_CATALOGIncorrect catalog name '%s'
1282HY000ER_WARN_QC_RESIZEQuery cache failed to set size %lu; new query cache size is %lu
1283HY000ER_BAD_FT_COLUMNColumn '%s' cannot be part of FULLTEXT index
1284HY000ER_UNKNOWN_KEY_CACHEUnknown key cache '%s'
1285HY000ER_WARN_HOSTNAME_WONT_WORKMariaDB is started in --skip-name-resolve mode; you must restart it without this switch for this grant to work
128642000ER_UNKNOWN_STORAGE_ENGINEUnknown storage engine '%s'
1287HY000ER_WARN_DEPRECATED_SYNTAX'%s' is deprecated and will be removed in a future release. Please use %s instead
1288HY000ER_NON_UPDATABLE_TABLEThe target table %s of the %s is not updatable
1289HY000ER_FEATURE_DISABLEDThe '%s' feature is disabled; you need MariaDB built with '%s' to have it working
1290HY000ER_OPTION_PREVENTS_STATEMENTThe MariaDB server is running with the %s option so it cannot execute this statement
1291HY000ER_DUPLICATED_VALUE_IN_TYPEColumn '%s' has duplicated value '%s' in %s
129222007ER_TRUNCATED_WRONG_VALUETruncated incorrect %s value: '%s'
1293HY000ER_TOO_MUCH_AUTO_TIMESTAMP_COLSIncorrect table definition; there can be only one TIMESTAMP column with CURRENT_TIMESTAMP in DEFAULT or ON UPDATE clause
1294HY000ER_INVALID_ON_UPDATEInvalid ON UPDATE clause for '%s' column
1295HY000ER_UNSUPPORTED_PSThis command is not supported in the prepared statement protocol yet
1296HY000ER_GET_ERRMSGGot error %d '%s' from %s
1297HY000ER_GET_TEMPORARY_ERRMSGGot temporary error %d '%s' from %s
1298HY000ER_UNKNOWN_TIME_ZONEUnknown or incorrect time zone: '%s'
1299HY000ER_WARN_INVALID_TIMESTAMPInvalid TIMESTAMP value in column '%s' at row %ld
Error CodeSQLSTATEErrorDescription
1300HY000ER_INVALID_CHARACTER_STRINGInvalid %s character string: '%s'
1301HY000ER_WARN_ALLOWED_PACKET_OVERFLOWEDResult of %s() was larger than max_allowed_packet (%ld) - truncated
1302HY000ER_CONFLICTING_DECLARATIONSConflicting declarations: '%s%s' and '%s%s'
13032F003ER_SP_NO_RECURSIVE_CREATECan't create a %s from within another stored routine
130442000ER_SP_ALREADY_EXISTS%s %s already exists
130542000ER_SP_DOES_NOT_EXIST%s %s does not exist
1306HY000ER_SP_DROP_FAILEDFailed to DROP %s %s
1307HY000ER_SP_STORE_FAILEDFailed to CREATE %s %s
130842000ER_SP_LILABEL_MISMATCH%s with no matching label: %s
130942000ER_SP_LABEL_REDEFINERedefining label %s
131042000ER_SP_LABEL_MISMATCHEnd-label %s without match
131101000ER_SP_UNINIT_VARReferring to uninitialized variable %s
13120A000ER_SP_BADSELECTPROCEDURE %s can't return a result set in the given context
131342000ER_SP_BADRETURNRETURN is only allowed in a FUNCTION
13140A000ER_SP_BADSTATEMENT%s is not allowed in stored procedures
131542000ER_UPDATE_LOG_DEPRECATED_IGNOREDThe update log is deprecated and replaced by the binary log; SET SQL_LOG_UPDATE has been ignored. This option will be removed in MariaDB 5.6.
131642000ER_UPDATE_LOG_DEPRECATED_TRANSLATEDThe update log is deprecated and replaced by the binary log; SET SQL_LOG_UPDATE has been translated to SET SQL_LOG_BIN. This option will be removed in MariaDB 5.6.
131770100ER_QUERY_INTERRUPTEDQuery execution was interrupted
131842000ER_SP_WRONG_NO_OF_ARGSIncorrect number of arguments for %s %s; expected %u, got %u
131942000ER_SP_COND_MISMATCHUndefined CONDITION: %s
132042000ER_SP_NORETURNNo RETURN found in FUNCTION %s
13212F005ER_SP_NORETURNENDFUNCTION %s ended without RETURN
132242000ER_SP_BAD_CURSOR_QUERYCursor statement must be a SELECT
132342000ER_SP_BAD_CURSOR_SELECTCursor SELECT must not have INTO
132442000ER_SP_CURSOR_MISMATCHUndefined CURSOR: %s
132524000ER_SP_CURSOR_ALREADY_OPENCursor is already open
132624000ER_SP_CURSOR_NOT_OPENCursor is not open
132742000ER_SP_UNDECLARED_VARUndeclared variable: %s
1328HY000ER_SP_WRONG_NO_OF_FETCH_ARGSIncorrect number of FETCH variables
132902000ER_SP_FETCH_NO_DATANo data - zero rows fetched, selected, or processed
133042000ER_SP_DUP_PARAMDuplicate parameter: %s
133142000ER_SP_DUP_VARDuplicate variable: %s
133242000ER_SP_DUP_CONDDuplicate condition: %s
133342000ER_SP_DUP_CURSDuplicate cursor: %s
1334HY000ER_SP_CANT_ALTERFailed to ALTER %s %s
13350A000ER_SP_SUBSELECT_NYISubquery value not supported
13360A000ER_STMT_NOT_ALLOWED_IN_SF_OR_TRG%s is not allowed in stored function or trigger
133742000ER_SP_VARCOND_AFTER_CURSHNDLRVariable or condition declaration after cursor or handler declaration
133842000ER_SP_CURSOR_AFTER_HANDLERCursor declaration after handler declaration
133920000ER_SP_CASE_NOT_FOUNDCase not found for CASE statement
1340HY000ER_FPARSER_TOO_BIG_FILEConfiguration file '%s' is too big
1341HY000ER_FPARSER_BAD_HEADERMalformed file type header in file '%s'
1342HY000ER_FPARSER_EOF_IN_COMMENTUnexpected end of file while parsing comment '%s'
1343HY000ER_FPARSER_ERROR_IN_PARAMETERError while parsing parameter '%s' (line: '%s')
1344HY000ER_FPARSER_EOF_IN_UNKNOWN_PARAMETERUnexpected end of file while skipping unknown parameter '%s'
1345HY000ER_VIEW_NO_EXPLAINEXPLAIN/SHOW can not be issued; lacking privileges for underlying table
1346HY000ER_FRM_UNKNOWN_TYPEFile '%s' has unknown type '%s' in its header
1347HY000ER_WRONG_OBJECT'%s.%s' is not %s
1348HY000ER_NONUPDATEABLE_COLUMNColumn '%s' is not updatable
1349HY000ER_VIEW_SELECT_DERIVEDView's SELECT contains a subquery in the FROM clause
1350HY000ER_VIEW_SELECT_CLAUSEView's SELECT contains a '%s' clause
1351HY000ER_VIEW_SELECT_VARIABLEView's SELECT contains a variable or parameter
1352HY000ER_VIEW_SELECT_TMPTABLEView's SELECT refers to a temporary table '%s'
1353HY000ER_VIEW_WRONG_LISTView's SELECT and view's field list have different column counts
1354HY000ER_WARN_VIEW_MERGEView merge algorithm can't be used here for now (assumed undefined algorithm)
1355HY000ER_WARN_VIEW_WITHOUT_KEYView being updated does not have complete key of underlying table in it
1356HY000ER_VIEW_INVALIDView '%s.%s' references invalid table(s) or column(s) or function(s) or definer/invoker of view lack rights to use them
1357HY000ER_SP_NO_DROP_SPCan't drop or alter a %s from within another stored routine
1358HY000ER_SP_GOTO_IN_HNDLRGOTO is not allowed in a stored procedure handler
1359HY000ER_TRG_ALREADY_EXISTSTrigger already exists
1360HY000ER_TRG_DOES_NOT_EXISTTrigger does not exist
1361HY000ER_TRG_ON_VIEW_OR_TEMP_TABLETrigger's '%s' is view or temporary table
1362HY000ER_TRG_CANT_CHANGE_ROWUpdating of %s row is not allowed in %strigger
1363HY000ER_TRG_NO_SUCH_ROW_IN_TRGThere is no %s row in %s trigger
1364HY000ER_NO_DEFAULT_FOR_FIELDField '%s' doesn't have a default value
136522012ER_DIVISION_BY_ZERDivision by 0
1366HY000ER_TRUNCATED_WRONG_VALUE_FOR_FIELDIncorrect %s value: '%s' for column '%s' at row %ld
136722007ER_ILLEGAL_VALUE_FOR_TYPEIllegal %s '%s' value found during parsing
1368HY000ER_VIEW_NONUPD_CHECKCHECK OPTION on non-updatable view '%s.%s'
1369HY000ER_VIEW_CHECK_FAILEDCHECK OPTION failed '%s.%s'
137042000ER_PROCACCESS_DENIED_ERROR%s command denied to user '%s'@'%s' for routine '%s'
1371HY000ER_RELAY_LOG_FAILFailed purging old relay logs: %s
1372HY000ER_PASSWD_LENGTHPassword hash should be a %d-digit hexadecimal number
1373HY000ER_UNKNOWN_TARGET_BINLOGTarget log not found in binlog index
1374HY000ER_IO_ERR_LOG_INDEX_READI/O error reading log index file
1375HY000ER_BINLOG_PURGE_PROHIBITEDServer configuration does not permit binlog purge
1376HY000ER_FSEEK_FAILFailed on fseek()
1377HY000ER_BINLOG_PURGE_FATAL_ERRFatal error during log purge
1378HY000ER_LOG_IN_USEA purgeable log is in use, will not purge
1379HY000ER_LOG_PURGE_UNKNOWN_ERRUnknown error during log purge
1380HY000ER_RELAY_LOG_INITFailed initializing relay log position: %s
1381HY000ER_NO_BINARY_LOGGINGYou are not using binary logging
1382HY000ER_RESERVED_SYNTAXThe '%s' syntax is reserved for purposes internal to the MariaDB server
1383HY000ER_WSAS_FAILEDWSAStartup Failed
1384HY000ER_DIFF_GROUPS_PROCCan't handle procedures with different groups yet
1385HY000ER_NO_GROUP_FOR_PROCSelect must have a group with this procedure
1386HY000ER_ORDER_WITH_PROCCan't use ORDER clause with this procedure
1387HY000ER_LOGGING_PROHIBIT_CHANGING_OFBinary logging and replication forbid changing the global server %s
1388HY000ER_NO_FILE_MAPPINGCan't map file: %s, errno: %d
1389HY000ER_WRONG_MAGICWrong magic in %s
1390HY000ER_PS_MANY_PARAMPrepared statement contains too many placeholders
1391HY000ER_KEY_PART_0Key part '%s' length cannot be 0
1392HY000ER_VIEW_CHECKSUMView text checksum failed
1393HY000ER_VIEW_MULTIUPDATECan not modify more than one base table through a join view '%s.%s'
1394HY000ER_VIEW_NO_INSERT_FIELD_LISTCan not insert into join view '%s.%s' without fields list
1395HY000ER_VIEW_DELETE_MERGE_VIEWCan not delete from join view '%s.%s'
1396HY000ER_CANNOT_USEROperation %s failed for %s
1397XAE04ER_XAER_NOTAXAER_NOTA: Unknown XID
1398XAE05ER_XAER_INVALXAER_INVAL: Invalid arguments (or unsupported command)
1399XAE07ER_XAER_RMFAILXAER_RMFAIL: The command cannot be executed when global transaction is in the %s state
Error CodeSQLSTATEErrorDescription
1400XAE09ER_XAER_OUTSIDEXAER_OUTSIDE: Some work is done outside global transaction
1401XAE03ER_XAER_RMERRXAER_RMERR: Fatal error occurred in the transaction branch - check your data for consistency
1402XA100ER_XA_RBROLLBACKXA_RBROLLBACK: Transaction branch was rolled back
140342000ER_NONEXISTING_PROC_GRANTThere is no such grant defined for user '%s' on host '%s' on routine '%s'
1404HY000ER_PROC_AUTO_GRANT_FAILFailed to grant EXECUTE and ALTER ROUTINE privileges
1405HY000ER_PROC_AUTO_REVOKE_FAILFailed to revoke all privileges to dropped routine
140622001ER_DATA_TOO_LONGData too long for column '%s' at row %ld
140742000ER_SP_BAD_SQLSTATEBad SQLSTATE: '%s'
1408HY000ER_STARTUP%s: ready for connections. Version: '%s' socket: '%s' port: %d %s
1409HY000ER_LOAD_FROM_FIXED_SIZE_ROWS_TO_VARCan't load value from file with fixed size rows to variable
141042000ER_CANT_CREATE_USER_WITH_GRANTYou are not allowed to create a user with GRANT
1411HY000ER_WRONG_VALUE_FOR_TYPEIncorrect %s value: '%s' for function %s
1412HY000ER_TABLE_DEF_CHANGEDTable definition has changed, please retry transaction
141342000ER_SP_DUP_HANDLERDuplicate handler declared in the same block
141442000ER_SP_NOT_VAR_ARGOUT or INOUT argument %d for routine %s is not a variable or NEW pseudo-variable in BEFORE trigger
14150A000ER_SP_NO_RETSETNot allowed to return a result set from a %s
141622003ER_CANT_CREATE_GEOMETRY_OBJECTCannot get geometry object from data you send to the GEOMETRY field
1417HY000ER_FAILED_ROUTINE_BREAK_BINLOGA routine failed and has neither NO SQL nor READS SQL DATA in its declaration and binary logging is enabled; if non-transactional tables were updated, the binary log will miss their changes
1418HY000ER_BINLOG_UNSAFE_ROUTINEThis function has none of DETERMINISTIC, NO SQL, or READS SQL DATA in its declaration and binary logging is enabled (you *might* want to use the less safe log_bin_trust_function_creators variable)
1419HY000ER_BINLOG_CREATE_ROUTINE_NEED_SUPERYou do not have the SUPER privilege and binary logging is enabled (you *might* want to use the less safe log_bin_trust_function_creators variable)
1420HY000ER_EXEC_STMT_WITH_OPEN_CURSORYou can't execute a prepared statement which has an open cursor associated with it. Reset the statement to re-execute it.
1421HY000ER_STMT_HAS_NO_OPEN_CURSORThe statement (%lu) has no open cursor.
1422HY000ER_COMMIT_NOT_ALLOWED_IN_SF_OR_TRGExplicit or implicit commit is not allowed in stored function or trigger.
1423HY000ER_NO_DEFAULT_FOR_VIEW_FIELDField of view '%s.%s' underlying table doesn't have a default value
1424HY000ER_SP_NO_RECURSIONRecursive stored functions and triggers are not allowed.
142542000ER_TOO_BIG_SCALEToo big scale %d specified for column '%s'. Maximum is %lu.
142642000ER_TOO_BIG_PRECISIONToo big precision %d specified for column '%s'. Maximum is %lu.
142742000ER_M_BIGGER_THAN_DFor float(M,D, double(M,D or decimal(M,D, M must be >= D (column '%s').
1428HY000ER_WRONG_LOCK_OF_SYSTEM_TABLEYou can't combine write-locking of system tables with other tables or lock types
1429HY000ER_CONNECT_TO_FOREIGN_DATA_SOURCEUnable to connect to foreign data source: %s
1430HY000ER_QUERY_ON_FOREIGN_DATA_SOURCEThere was a problem processing the query on the foreign data source. Data source error: %s
1431HY000ER_FOREIGN_DATA_SOURCE_DOESNT_EXISTThe foreign data source you are trying to reference does not exist. Data source error: %s
1432HY000ER_FOREIGN_DATA_STRING_INVALID_CANT_CREATECan't create federated table. The data source connection string '%s' is not in the correct format
1433HY000ER_FOREIGN_DATA_STRING_INVALIDThe data source connection string '%s' is not in the correct format
1434HY000ER_CANT_CREATE_FEDERATED_TABLECan't create federated table. Foreign data src error: %s
1435HY000ER_TRG_IN_WRONG_SCHEMATrigger in wrong schema
1436HY000ER_STACK_OVERRUN_NEED_MOREThread stack overrun: %ld bytes used of a %ld byte stack, and %ld bytes needed. Use 'mysqld --thread_stack=#' to specify a bigger stack.
143742000ER_TOO_LONG_BODYRoutine body for '%s' is too long
1438HY000ER_WARN_CANT_DROP_DEFAULT_KEYCACHECannot drop default keycache
143942000ER_TOO_BIG_DISPLAYWIDTHDisplay width out of range for column '%s' (max = %lu)
1440XAE08ER_XAER_DUPIDXAER_DUPID: The XID already exists
144122008ER_DATETIME_FUNCTION_OVERFLOWDatetime function: %s field overflow
1442HY000ER_CANT_UPDATE_USED_TABLE_IN_SF_OR_TRGCan't update table '%s' in stored function/trigger because it is already used by statement which invoked this stored function/trigger.
1443HY000ER_VIEW_PREVENT_UPDATEThe definition of table '%s' prevents operation %s on table '%s'.
1444HY000ER_PS_NO_RECURSIONThe prepared statement contains a stored routine call that refers to that same statement. It's not allowed to execute a prepared statement in such a recursive manner
1445HY000ER_SP_CANT_SET_AUTOCOMMITNot allowed to set autocommit from a stored function or trigger
1446HY000ER_MALFORMED_DEFINERDefiner is not fully qualified
1447HY000ER_VIEW_FRM_NO_USERView '%s'.'%s' has no definer information (old table format). Current user is used as definer. Please recreate the view!
1448HY000ER_VIEW_OTHER_USERYou need the SUPER privilege for creation view with '%s'@'%s' definer
1449HY000ER_NO_SUCH_USERThe user specified as a definer ('%s'@'%s') does not exist
1450HY000ER_FORBID_SCHEMA_CHANGEChanging schema from '%s' to '%s' is not allowed.
145123000ER_ROW_IS_REFERENCED_2Cannot delete or update a parent row: a foreign key constraint fails (%s)
145223000ER_NO_REFERENCED_ROW_2Cannot add or update a child row: a foreign key constraint fails (%s)
145342000ER_SP_BAD_VAR_SHADOWVariable '%s' must be quoted with `...`, or renamed
1454HY000ER_TRG_NO_DEFINERNo definer attribute for trigger '%s'.'%s'. The trigger will be activated under the authorization of the invoker, which may have insufficient privileges. Please recreate the trigger.
1455HY000ER_OLD_FILE_FORMAT'%s' has an old format, you should re-create the '%s' object(s)
1456HY000ER_SP_RECURSION_LIMITRecursive limit %d (as set by the max_sp_recursion_depth variable) was exceeded for routine %s
1457HY000ER_SP_PROC_TABLE_CORRUPTFailed to load routine %s. The table mysql.proc is missing, corrupt, or contains bad data (internal code %d)
145842000ER_SP_WRONG_NAMEIncorrect routine name '%s'
1459HY000ER_TABLE_NEEDS_UPGRADETable upgrade required. Please do "REPAIR TABLE `%s`" or dump/reload to fix it!
146042000ER_SP_NO_AGGREGATEAGGREGATE is not supported for stored functions
146142000ER_MAX_PREPARED_STMT_COUNT_REACHEDCan't create more than max_prepared_stmt_count statements (current value: %lu)
1462HY000ER_VIEW_RECURSIVE`%s`.`%s` contains view recursion
146342000ER_NON_GROUPING_FIELD_USEDNon-grouping field '%s' is used in %s clause
1464HY000ER_TABLE_CANT_HANDLE_SPKEYSThe used table type doesn't support SPATIAL indexes
1465HY000ER_NO_TRIGGERS_ON_SYSTEM_SCHEMATriggers can not be created on system tables
1466HY000ER_REMOVED_SPACESLeading spaces are removed from name '%s'
1467HY000ER_AUTOINC_READ_FAILEDFailed to read auto-increment value from storage engine
1468HY000ER_USERNAMEuser name
1469HY000ER_HOSTNAMEhost name
1470HY000ER_WRONG_STRING_LENGTHString '%s' is too long for %s (should be no longer than %d)
1471HY000ER_NON_INSERTABLE_TABLEThe target table %s of the %s is not insertable-into
1472HY000ER_ADMIN_WRONG_MRG_TABLETable '%s' is differently defined or of non-MyISAM type or doesn't exist
1473HY000ER_TOO_HIGH_LEVEL_OF_NESTING_FOR_SELECTToo high level of nesting for select
1474HY000ER_NAME_BECOMES_EMPTYName '%s' has become ''
1475HY000ER_AMBIGUOUS_FIELD_TERMFirst character of the FIELDS TERMINATED string is ambiguous; please use non-optional and non-empty FIELDS ENCLOSED BY
1476HY000ER_FOREIGN_SERVER_EXISTSThe foreign server, %s, you are trying to create already exists.
1477HY000ER_FOREIGN_SERVER_DOESNT_EXISTThe foreign server name you are trying to reference does not exist. Data source error: %s
1478HY000ER_ILLEGAL_HA_CREATE_OPTIONTable storage engine '%s' does not support the create option '%s'
1479HY000ER_PARTITION_REQUIRES_VALUES_ERRORSyntax error: %s PARTITIONING requires definition of VALUES %s for each partition
1480HY000ER_PARTITION_WRONG_VALUES_ERROROnly %s PARTITIONING can use VALUES %s in partition definition
1481HY000ER_PARTITION_MAXVALUE_ERRORMAXVALUE can only be used in last partition definition
1482HY000ER_PARTITION_SUBPARTITION_ERRORSubpartitions can only be hash partitions and by key
1483HY000ER_PARTITION_SUBPART_MIX_ERRORMust define subpartitions on all partitions if on one partition
1484HY000ER_PARTITION_WRONG_NO_PART_ERRORWrong number of partitions defined, mismatch with previous setting
1485HY000ER_PARTITION_WRONG_NO_SUBPART_ERRORWrong number of subpartitions defined, mismatch with previous setting
1486HY000ER_CONST_EXPR_IN_PARTITION_FUNC_ERRORConstant/Random expression in (sub)partitioning function is not allowed
1486HY000ER_WRONG_EXPR_IN_PARTITION_FUNC_ERRORConstant, random or timezone-dependent expressions in (sub)partitioning function are not allowed
1487HY000ER_NO_CONST_EXPR_IN_RANGE_OR_LIST_ERRORExpression in RANGE/LIST VALUES must be constant
1488HY000ER_FIELD_NOT_FOUND_PART_ERRORField in list of fields for partition function not found in table
1489HY000ER_LIST_OF_FIELDS_ONLY_IN_HASH_ERRORList of fields is only allowed in KEY partitions
1490HY000ER_INCONSISTENT_PARTITION_INFO_ERRORThe partition info in the frm file is not consistent with what can be written into the frm file
1491HY000ER_PARTITION_FUNC_NOT_ALLOWED_ERRORThe %s function returns the wrong type
1492HY000ER_PARTITIONS_MUST_BE_DEFINED_ERRORFor %s partitions each partition must be defined
1493HY000ER_RANGE_NOT_INCREASING_ERRORVALUES LESS THAN value must be strictly increasing for each partition
1494HY000ER_INCONSISTENT_TYPE_OF_FUNCTIONS_ERRORVALUES value must be of same type as partition function
1495HY000ER_MULTIPLE_DEF_CONST_IN_LIST_PART_ERRORMultiple definition of same constant in list partitioning
1496HY000ER_PARTITION_ENTRY_ERRORPartitioning can not be used stand-alone in query
1497HY000ER_MIX_HANDLER_ERRORThe mix of handlers in the partitions is not allowed in this version of MariaDB
1498HY000ER_PARTITION_NOT_DEFINED_ERRORFor the partitioned engine it is necessary to define all %s
1499HY000ER_TOO_MANY_PARTITIONS_ERRORToo many partitions (including subpartitions) were defined
Error CodeSQLSTATEErrorDescription
1500HY000ER_SUBPARTITION_ERRORIt is only possible to mix RANGE/LIST partitioning with HASH/KEY partitioning for subpartitioning
1501HY000ER_CANT_CREATE_HANDLER_FILEFailed to create specific handler file
1502HY000ER_BLOB_FIELD_IN_PART_FUNC_ERRORA BLOB field is not allowed in partition function
1503HY000ER_UNIQUE_KEY_NEED_ALL_FIELDS_IN_PFA %s must include all columns in the table's partitioning function
1504HY000ER_NO_PARTS_ERRORNumber of %s = 0 is not an allowed value
1505HY000ER_PARTITION_MGMT_ON_NONPARTITIONEDPartition management on a not partitioned table is not possible
1506HY000ER_FOREIGN_KEY_ON_PARTITIONEDForeign key clause is not yet supported in conjunction with partitioning
1507HY000ER_DROP_PARTITION_NON_EXISTENTError in list of partitions to %s
1508HY000ER_DROP_LAST_PARTITIONCannot remove all partitions, use DROP TABLE instead
1509HY000ER_COALESCE_ONLY_ON_HASH_PARTITIONCOALESCE PARTITION can only be used on HASH/KEY partitions
1510HY000ER_REORG_HASH_ONLY_ON_SAME_NREORGANIZE PARTITION can only be used to reorganize partitions not to change their numbers
1511HY000ER_REORG_NO_PARAM_ERRORREORGANIZE PARTITION without parameters can only be used on auto-partitioned tables using HASH PARTITIONs
1512HY000ER_ONLY_ON_RANGE_LIST_PARTITION%s PARTITION can only be used on RANGE/LIST partitions
1513HY000ER_ADD_PARTITION_SUBPART_ERRORTrying to Add partition(s) with wrong number of subpartitions
1514HY000ER_ADD_PARTITION_NO_NEW_PARTITIONAt least one partition must be added
1515HY000ER_COALESCE_PARTITION_NO_PARTITIONAt least one partition must be coalesced
1516HY000ER_REORG_PARTITION_NOT_EXISTMore partitions to reorganize than there are partitions
1517HY000ER_SAME_NAME_PARTITIONDuplicate partition name %s
1518HY000ER_NO_BINLOG_ERRORIt is not allowed to shut off binlog on this command
1519HY000ER_CONSECUTIVE_REORG_PARTITIONSWhen reorganizing a set of partitions they must be in consecutive order
1520HY000ER_REORG_OUTSIDE_RANGEReorganize of range partitions cannot change total ranges except for last partition where it can extend the range
1521HY000ER_PARTITION_FUNCTION_FAILUREPartition function not supported in this version for this handler
1522HY000ER_PART_STATE_ERRORPartition state cannot be defined from CREATE/ALTER TABLE
1523HY000ER_LIMITED_PART_RANGEThe %s handler only supports 32 bit integers in VALUES
1524HY000ER_PLUGIN_IS_NOT_LOADEDPlugin '%s' is not loaded
1525HY000ER_WRONG_VALUEIncorrect %s value: '%s'
1526HY000ER_NO_PARTITION_FOR_GIVEN_VALUETable has no partition for value %s
1527HY000ER_FILEGROUP_OPTION_ONLY_ONCEIt is not allowed to specify %s more than once
1528HY000ER_CREATE_FILEGROUP_FAILEDFailed to create %s
1529HY000ER_DROP_FILEGROUP_FAILEDFailed to drop %s
1530HY000ER_TABLESPACE_AUTO_EXTEND_ERRORThe handler doesn't support autoextend of tablespaces
1531HY000ER_WRONG_SIZE_NUMBERA size parameter was incorrectly specified, either number or on the form 10M
1532HY000ER_SIZE_OVERFLOW_ERRORThe size number was correct but we don't allow the digit part to be more than 2 billion
1533HY000ER_ALTER_FILEGROUP_FAILEDFailed to alter: %s
1534HY000ER_BINLOG_ROW_LOGGING_FAILEDWriting one row to the row-based binary log failed
1535HY000ER_BINLOG_ROW_WRONG_TABLE_DEFTable definition on master and slave does not match: %s
1536HY000ER_BINLOG_ROW_RBR_TO_SBRSlave running with --log-slave-updates must use row-based binary logging to be able to replicate row-based binary log events
1537HY000ER_EVENT_ALREADY_EXISTSEvent '%s' already exists
1538HY000ER_EVENT_STORE_FAILEDFailed to store event %s. Error code %d from storage engine.
1539HY000ER_EVENT_DOES_NOT_EXISTUnknown event '%s'
1540HY000ER_EVENT_CANT_ALTERFailed to alter event '%s'
1541HY000ER_EVENT_DROP_FAILEDFailed to drop %s
1542HY000ER_EVENT_INTERVAL_NOT_POSITIVE_OR_TOO_BIGINTERVAL is either not positive or too big
1543HY000ER_EVENT_ENDS_BEFORE_STARTSENDS is either invalid or before STARTS
1544HY000ER_EVENT_EXEC_TIME_IN_THE_PASTEvent execution time is in the past. Event has been disabled
1545HY000ER_EVENT_OPEN_TABLE_FAILEDFailed to open mysql.event
1546HY000ER_EVENT_NEITHER_M_EXPR_NOR_M_ATNo datetime expression provided
1547HY000ER_COL_COUNT_DOESNT_MATCH_CORRUPTEDColumn count of mysql.%s is wrong. Expected %d, found %d. The table is probably corrupted
1548HY000ER_CANNOT_LOAD_FROM_TABLECannot load from mysql.%s. The table is probably corrupted
1549HY000ER_EVENT_CANNOT_DELETEFailed to delete the event from mysql.event
1550HY000ER_EVENT_COMPILE_ERRORError during compilation of event's body
1551HY000ER_EVENT_SAME_NAMESame old and new event name
1552HY000ER_EVENT_DATA_TOO_LONGData for column '%s' too long
1553HY000ER_DROP_INDEX_FKCannot drop index '%s': needed in a foreign key constraint
1554HY000ER_WARN_DEPRECATED_SYNTAX_WITH_VERThe syntax '%s' is deprecated and will be removed in MariaDB %s. Please use %s instead
1555HY000ER_CANT_WRITE_LOCK_LOG_TABLEYou can't write-lock a log table. Only read access is possible
1556HY000ER_CANT_LOCK_LOG_TABLEYou can't use locks with log tables.
155723000ER_FOREIGN_DUPLICATE_KEYUpholding foreign key constraints for table '%s', entry '%s', key %d would lead to a duplicate entry
1558HY000ER_COL_COUNT_DOESNT_MATCH_PLEASE_UPDATEColumn count of mysql.%s is wrong. Expected %d, found %d. Created with MariaDB %d, now running %d. Please use mysql_upgrade to fix this error.
1559HY000ER_TEMP_TABLE_PREVENTS_SWITCH_OUT_OF_RBRCannot switch out of the row-based binary log format when the session has open temporary tables
1560HY000ER_STORED_FUNCTION_ PREVENTS_SWITCH_BINLOG_FORMATCannot change the binary logging format inside a stored function or trigger
1561ER_UNUSED_13You should never see it
1562HY000ER_PARTITION_NO_TEMPORARYCannot create temporary table with partitions
1563HY000ER_PARTITION_CONST_DOMAIN_ERRORPartition constant is out of partition function domain
1564HY000ER_PARTITION_FUNCTION_IS_NOT_ALLOWEDThis partition function is not allowed
1565HY000ER_DDL_LOG_ERRORError in DDL log
1566HY000ER_NULL_IN_VALUES_LESS_THANNot allowed to use NULL value in VALUES LESS THAN
1567HY000ER_WRONG_PARTITION_NAMEIncorrect partition name
156825001ER_CANT_CHANGE_TX_ISOLATIONTransaction isolation level can't be changed while a transaction is in progress
1569HY000ER_DUP_ENTRY_AUTOINCREMENT_CASEALTER TABLE causes auto_increment resequencing, resulting in duplicate entry '%s' for key '%s'
1570HY000ER_EVENT_MODIFY_QUEUE_ERRORInternal scheduler error %d
1571HY000ER_EVENT_SET_VAR_ERRORError during starting/stopping of the scheduler. Error code %u
1572HY000ER_PARTITION_MERGE_ERROREngine cannot be used in partitioned tables
1573HY000ER_CANT_ACTIVATE_LOGCannot activate '%s' log
1574HY000ER_RBR_NOT_AVAILABLEThe server was not built with row-based replication
1575HY000ER_BASE64_DECODE_ERRORDecoding of base64 string failed
1576HY000ER_EVENT_RECURSION_FORBIDDENRecursion of EVENT DDL statements is forbidden when body is present
1577HY000ER_EVENTS_DB_ERRORCannot proceed because system tables used by Event Scheduler were found damaged at server start
1578HY000ER_ONLY_INTEGERS_ALLOWEDOnly integers allowed as number here
1579HY000ER_UNSUPORTED_LOG_ENGINEThis storage engine cannot be used for log tables"
1580HY000ER_BAD_LOG_STATEMENTYou cannot '%s' a log table if logging is enabled
1581HY000ER_CANT_RENAME_LOG_TABLECannot rename '%s'. When logging enabled, rename to/from log table must rename two tables: the log table to an archive table and another table back to '%s'
158242000ER_WRONG_PARAMCOUNT_TO_NATIVE_FCTIncorrect parameter count in the call to native function '%s'
158342000ER_WRONG_PARAMETERS_TO_NATIVE_FCTIncorrect parameters in the call to native function '%s'
158442000ER_WRONG_PARAMETERS_TO_STORED_FCTIncorrect parameters in the call to stored function '%s'
1585HY000ER_NATIVE_FCT_NAME_COLLISIONThis function '%s' has the same name as a native function
158623000ER_DUP_ENTRY_WITH_KEY_NAMEDuplicate entry '%s' for key '%s'
1587HY000ER_BINLOG_PURGE_EMFILEToo many files opened, please execute the command again
1588HY000ER_EVENT_CANNOT_CREATE_IN_THE_PASTEvent execution time is in the past and ON COMPLETION NOT PRESERVE is set. The event was dropped immediately after creation.
1589HY000ER_EVENT_CANNOT_ALTER_IN_THE_PASTEvent execution time is in the past and ON COMPLETION NOT PRESERVE is set. The event was dropped immediately after creation.
1590HY000ER_SLAVE_INCIDENTThe incident %s occured on the master. Message: %s
1591HY000ER_NO_PARTITION_FOR_GIVEN_VALUE_SILENTTable has no partition for some existing values
1592HY000ER_BINLOG_UNSAFE_STATEMENTUnsafe statement written to the binary log using statement format since BINLOG_FORMAT = STATEMENT. %s
1593HY000ER_SLAVE_FATAL_ERRORFatal error: %s
1594HY000ER_SLAVE_RELAY_LOG_READ_FAILURERelay log read failure: %s
1595HY000ER_SLAVE_RELAY_LOG_WRITE_FAILURERelay log write failure: %s
1596HY000ER_SLAVE_CREATE_EVENT_FAILUREFailed to create %s
1597HY000ER_SLAVE_MASTER_COM_FAILUREMaster command %s failed: %s
1598HY000ER_BINLOG_LOGGING_IMPOSSIBLEBinary logging not possible. Message: %s
1599HY000ER_VIEW_NO_CREATION_CTXView `%s`.`%s` has no creation context
Error CodeSQLSTATEErrorDescription
1600HY000ER_VIEW_INVALID_CREATION_CTXCreation context of view `%s`.`%s' is invalid
1601HY000ER_SR_INVALID_CREATION_CTXCreation context of stored routine `%s`.`%s` is invalid
1602HY000ER_TRG_CORRUPTED_FILECorrupted TRG file for table `%s`.`%s`
1603HY000ER_TRG_NO_CREATION_CTXTriggers for table `%s`.`%s` have no creation context
1604HY000ER_TRG_INVALID_CREATION_CTXTrigger creation context of table `%s`.`%s` is invalid
1605HY000ER_EVENT_INVALID_CREATION_CTXCreation context of event `%s`.`%s` is invalid
1606HY000ER_TRG_CANT_OPEN_TABLECannot open table for trigger `%s`.`%s`
1607HY000ER_CANT_CREATE_SROUTINECannot create stored routine `%s`. Check warnings
1608ER_UNUSED_11You should never see it
1609HY000ER_NO_FORMAT_DESCRIPTION_EVENT _BEFORE_BINLOG_STATEMENTThe BINLOG statement of type `%s` was not preceded by a format description BINLOG statement.
1610HY000ER_SLAVE_CORRUPT_EVENTCorrupted replication event was detected
1611HY000ER_LOAD_DATA_INVALID_COLUMNInvalid column reference (%s) in LOAD DATA
1612HY000ER_LOG_PURGE_NO_FILEBeing purged log %s was not found
1613XA106ER_XA_RBTIMEOUTXA_RBTIMEOUT: Transaction branch was rolled back: took too long
1614XA102ER_XA_RBDEADLOCKXA_RBDEADLOCK: Transaction branch was rolled back: deadlock was detected
1615HY000ER_NEED_REPREPAREPrepared statement needs to be re-prepared
1616HY000ER_DELAYED_NOT_SUPPORTEDDELAYED option not supported for table '%s'
1617HY000WARN_NO_MASTER_INFThe master info structure does not exist
1618HY000WARN_OPTION_IGNORED<%s> option ignored
1619HY000WARN_PLUGIN_DELETE_BUILTINBuilt-in plugins cannot be deleted
1620HY000WARN_PLUGIN_BUSYPlugin is busy and will be uninstalled on shutdown
1621HY000ER_VARIABLE_IS_READONLY%s variable '%s' is read-only. Use SET %s to assign the value
1622HY000ER_WARN_ENGINE_TRANSACTION_ROLLBACKStorage engine %s does not support rollback for this statement. Transaction rolled back and must be restarted
1623HY000ER_SLAVE_HEARTBEAT_FAILUREUnexpected master's heartbeat data: %s
1624HY000ER_SLAVE_HEARTBEAT_VALUE_OUT_OF_RANGEThe requested value for the heartbeat period is either negative or exceeds the maximum allowed (%s seconds).
1625ER_UNUSED_14You should never see it
1626HY000ER_CONFLICT_FN_PARSE_ERRORError in parsing conflict function. Message: %s
1627HY000ER_EXCEPTIONS_WRITE_ERRORWrite to exceptions table failed. Message: %s"
1628HY000ER_TOO_LONG_TABLE_COMMENTComment for table '%s' is too long (max = %lu)
1629HY000ER_TOO_LONG_FIELD_COMMENTComment for field '%s' is too long (max = %lu)
163042000ER_FUNC_INEXISTENT_NAME_COLLISIONFUNCTION %s does not exist. Check the 'Function Name Parsing and Resolution' section in the Reference Manual
1631HY000ER_DATABASE_NAMEDatabase
1632HY000ER_TABLE_NAMETable
1633HY000ER_PARTITION_NAMEPartition
1634HY000ER_SUBPARTITION_NAMESubpartition
1635HY000ER_TEMPORARY_NAMETemporary
1636HY000ER_RENAMED_NAMERenamed
1637HY000ER_TOO_MANY_CONCURRENT_TRXSToo many active concurrent transactions
1638HY000WARN_NON_ASCII_SEPARATOR_NOT_IMPLEMENTEDNon-ASCII separator arguments are not fully supported
1639HY000ER_DEBUG_SYNC_TIMEOUTdebug sync point wait timed out
1640HY000ER_DEBUG_SYNC_HIT_LIMITdebug sync point hit limit reached
164142000ER_DUP_SIGNAL_SETDuplicate condition information item '%s'
164201000ER_SIGNAL_WARNUnhandled user-defined warning condition
164302000ER_SIGNAL_NOT_FOUNDUnhandled user-defined not found condition
1644HY000ER_SIGNAL_EXCEPTIONUnhandled user-defined exception condition
16450K000ER_RESIGNAL_WITHOUT_ACTIVE_HANDLERRESIGNAL when handler not active
1646HY000ER_SIGNAL_BAD_CONDITION_TYPESIGNAL/RESIGNAL can only use a CONDITION defined with SQLSTATE
1647HY000WARN_COND_ITEM_TRUNCATEDData truncated for condition item '%s'
1648HY000ER_COND_ITEM_TOO_LONGData too long for condition item '%s'
1649HY000ER_UNKNOWN_LOCALEUnknown locale: '%s'
1650HY000ER_SLAVE_IGNORE_SERVER_IDSThe requested server id %d clashes with the slave startup option --replicate-same-server-id
1651HY000ER_QUERY_CACHE_DISABLEDQuery cache is disabled; restart the server with query_cache_type=1 to enable it
1652HY000ER_SAME_NAME_PARTITION_FIELDDuplicate partition field name '%s'
1653HY000ER_PARTITION_COLUMN_LIST_ERRORInconsistency in usage of column lists for partitioning
1654HY000ER_WRONG_TYPE_COLUMN_VALUE_ERRORPartition column values of incorrect type
1655HY000ER_TOO_MANY_PARTITION_FUNC_FIELDS_ERRORToo many fields in '%s'
1656HY000ER_MAXVALUE_IN_VALUES_INCannot use MAXVALUE as value in VALUES IN
1657HY000ER_TOO_MANY_VALUES_ERRORCannot have more than one value for this type of %s partitioning
1658HY000ER_ROW_SINGLE_PARTITION_FIELD_ERRORRow expressions in VALUES IN only allowed for multi-field column partitioning
1659HY000ER_FIELD_TYPE_NOT_ALLOWED_AS_PARTITION_FIELDField '%s' is of a not allowed type for this type of partitioning
1660HY000ER_PARTITION_FIELDS_TOO_LONGThe total length of the partitioning fields is too large
1661HY000ER_BINLOG_ROW_ENGINE_AND_STMT_ENGINECannot execute statement: impossible to write to binary log since both row-incapable engines and statement-incapable engines are involved.
1662HY000ER_BINLOG_ROW_MODE_AND_STMT_ENGINECannot execute statement: impossible to write to binary log since BINLOG_FORMAT = ROW and at least one table uses a storage engine limited to statement-based logging.
1663HY000ER_BINLOG_UNSAFE_AND_STMT_ENGINECannot execute statement: impossible to write to binary log since statement is unsafe, storage engine is limited to statement-based logging, and BINLOG_FORMAT = MIXED. %s
1664HY000ER_BINLOG_ROW_INJECTION_AND_STMT_ENGINECannot execute statement: impossible to write to binary log since statement is in row format and at least one table uses a storage engine limited to statement-based logging.
1665HY000ER_BINLOG_STMT_MODE_AND_ROW_ENGINECannot execute statement: impossible to write to binary log since BINLOG_FORMAT = STATEMENT and at least one table uses a storage engine limited to row-based logging.%s
1666HY000ER_BINLOG_ROW_INJECTION_AND_STMT_MODECannot execute statement: impossible to write to binary log since statement is in row format and BINLOG_FORMAT = STATEMENT.
1667HY000ER_BINLOG_MULTIPLE_ENGINES _AND_SELF_LOGGING_ENGINECannot execute statement: impossible to write to binary log since more than one engine is involved and at least one engine is self-logging.
1668HY000ER_BINLOG_UNSAFE_LIMITThe statement is unsafe because it uses a LIMIT clause. This is unsafe because the set of rows included cannot be predicted.
1669HY000ER_BINLOG_UNSAFE_INSERT_DELAYEDThe statement is unsafe because it uses INSERT DELAYED. This is unsafe because the times when rows are inserted cannot be predicted.
1670HY000ER_BINLOG_UNSAFE_SYSTEM_TABLEThe statement is unsafe because it uses the general log, slow query log, or performance_schema table(s). This is unsafe because system tables may differ on slaves.
1671HY000ER_BINLOG_UNSAFE_AUTOINC_COLUMNSStatement is unsafe because it invokes a trigger or a stored function that inserts into an AUTO_INCREMENT column. Inserted values cannot be logged correctly.
1672HY000ER_BINLOG_UNSAFE_UDFStatement is unsafe because it uses a UDF which may not return the same value on the slave.
1673HY000ER_BINLOG_UNSAFE_SYSTEM_VARIABLEStatement is unsafe because it uses a system variable that may have a different value on the slave.
1674HY000ER_BINLOG_UNSAFE_SYSTEM_FUNCTIONStatement is unsafe because it uses a system function that may return a different value on the slave.
1675HY000ER_BINLOG_UNSAFE_NONTRANS_AFTER_TRANSStatement is unsafe because it accesses a non-transactional table after accessing a transactional table within the same transaction.
1676HY000ER_MESSAGE_AND_STATEMENT%s Statement: %s
1677HY000ER_SLAVE_CONVERSION_FAILEDColumn %d of table '%s.%s' cannot be converted from type '%s' to type '%s'
1678HY000ER_SLAVE_CANT_CREATE_CONVERSIONCan't create conversion table for table '%s.%s'
1679HY000ER_INSIDE_TRANSACTION _PREVENTS_SWITCH_BINLOG_FORMATCannot modify @@session.binlog_format inside a transaction
1680HY000ER_PATH_LENGTHThe path specified for %s is too long.
1681HY000ER_WARN_DEPRECATED_SYNTAX_NO_REPLACEMENT'%s' is deprecated and will be removed in a future release.
1682HY000ER_WRONG_NATIVE_TABLE_STRUCTURENative table '%s'.'%s' has the wrong structure
1683HY000ER_WRONG_PERFSCHEMA_USAGEInvalid performance_schema usage.
1684HY000ER_WARN_I_S_SKIPPED_TABLETable '%s'.'%s' was skipped since its definition is being modified by concurrent DDL statement
1685HY000ER_INSIDE_TRANSACTION _PREVENTS_SWITCH_BINLOG_DIRECTCannot modify @@session.binlog_direct_non_transactional_updates inside a transaction
1686HY000ER_STORED_FUNCTION_PREVENTS _SWITCH_BINLOG_DIRECTCannot change the binlog direct flag inside a stored function or trigger
168742000ER_SPATIAL_MUST_HAVE_GEOM_COLA SPATIAL index may only contain a geometrical type column
1688HY000ER_TOO_LONG_INDEX_COMMENTComment for index '%s' is too long (max = %lu)
1689HY000ER_LOCK_ABORTEDWait on a lock was aborted due to a pending exclusive lock
169022003ER_DATA_OUT_OF_RANGE%s value is out of range in '%s'
1691HY000ER_WRONG_SPVAR_TYPE_IN_LIMITA variable of a non-integer based type in LIMIT clause
1692HY000ER_BINLOG_UNSAFE_MULTIPLE_ENGINES _AND_SELF_LOGGING_ENGINEMixing self-logging and non-self-logging engines in a statement is unsafe.
1693HY000ER_BINLOG_UNSAFE_MIXED_STATEMENTStatement accesses nontransactional table as well as transactional or temporary table, and writes to any of them.
1694HY000ER_INSIDE_TRANSACTION_ PREVENTS_SWITCH_SQL_LOG_BINCannot modify @@session.sql_log_bin inside a transaction
1695HY000ER_STORED_FUNCTION_ PREVENTS_SWITCH_SQL_LOG_BINCannot change the sql_log_bin inside a stored function or trigger
1696HY000ER_FAILED_READ_FROM_PAR_FILEFailed to read from the .par file
1697HY000ER_VALUES_IS_NOT_INT_TYPE_ERRORVALUES value for partition '%s' must have type INT
169828000ER_ACCESS_DENIED_NO_PASSWORD_ERRORAccess denied for user '%s'@'%s'
1699HY000ER_SET_PASSWORD_AUTH_PLUGINSET PASSWORD has no significance for users authenticating via plugins
Error CodeSQLSTATEErrorDescription
1700HY000ER_GRANT_PLUGIN_USER_EXISTSGRANT with IDENTIFIED WITH is illegal because the user %-.*s already exists
170142000ER_TRUNCATE_ILLEGAL_FKCannot truncate a table referenced in a foreign key constraint (%s)
1702HY000ER_PLUGIN_IS_PERMANENTPlugin '%s' is force_plus_permanent and can not be unloaded
1703HY000ER_SLAVE_HEARTBEAT_VALUE_OUT_OF_RANGE_MINThe requested value for the heartbeat period is less than 1 millisecond. The value is reset to 0, meaning that heartbeating will effectively be disabled.
1704HY000ER_SLAVE_HEARTBEAT_VALUE_OUT_OF_RANGE_MAXThe requested value for the heartbeat period exceeds the value of slave_net_timeout seconds. A sensible value for the period should be less than the timeout.
1705HY000ER_STMT_CACHE_FULLMulti-row statements required more than 'max_binlog_stmt_cache_size' bytes of storage; increase this mysqld variable and try again
1706HY000ER_MULTI_UPDATE_KEY_CONFLICTPrimary key/partition key update is not allowed since the table is updated both as '%s' and '%s'.
1707HY000ER_TABLE_NEEDS_REBUILDTable rebuild required. Please do "ALTER TABLE `%s` FORCE" or dump/reload to fix it!
1708HY000WARN_OPTION_BELOW_LIMITThe value of '%s' should be no less than the value of '%s'
1709HY000ER_INDEX_COLUMN_TOO_LONGIndex column size too large. The maximum column size is %lu bytes.
1710HY000ER_ERROR_IN_TRIGGER_BODYTrigger '%s' has an error in its body: '%s'
1711HY000ER_ERROR_IN_UNKNOWN_TRIGGER_BODYUnknown trigger has an error in its body: '%s'
1712HY000ER_INDEX_CORRUPTIndex %s is corrupted
1713HY000ER_UNDO_RECORD_TOO_BIGUndo log record is too big.
1714HY000ER_BINLOG_UNSAFE_INSERT_IGNORE_SELECTINSERT IGNORE... SELECT is unsafe because the order in which rows are retrieved by the SELECT determines which (if any) rows are ignored. This order cannot be predicted and may differ on master and the slave.
1715HY000ER_BINLOG_UNSAFE_INSERT_SELECT_UPDATEINSERT... SELECT... ON DUPLICATE KEY UPDATE is unsafe because the order in which rows are retrieved by the SELECT determines which (if any) rows are updated. This order cannot be predicted and may differ on master and the slave.
1716HY000ER_BINLOG_UNSAFE_REPLACE_SELECTREPLACE... SELECT is unsafe because the order in which rows are retrieved by the SELECT determines which (if any) rows are replaced. This order cannot be predicted and may differ on master and the slave.
1717HY000ER_BINLOG_UNSAFE_CREATE_IGNORE_SELECTCREATE... IGNORE SELECT is unsafe because the order in which rows are retrieved by the SELECT determines which (if any) rows are ignored. This order cannot be predicted and may differ on master and the slave.
1718HY000ER_BINLOG_UNSAFE_CREATE_REPLACE_SELECTCREATE... REPLACE SELECT is unsafe because the order in which rows are retrieved by the SELECT determines which (if any) rows are replaced. This order cannot be predicted and may differ on master and the slave.
1719HY000ER_BINLOG_UNSAFE_UPDATE_IGNOREUPDATE IGNORE is unsafe because the order in which rows are updated determines which (if any) rows are ignored. This order cannot be predicted and may differ on master and the slave.
1720ER_UNUSED_15You should never see it
1721ER_UNUSED_16You should never see it
1722HY000ER_BINLOG_UNSAFE_WRITE_AUTOINC_SELECTStatements writing to a table with an auto-increment column after selecting from another table are unsafe because the order in which rows are retrieved determines what (if any) rows will be written. This order cannot be predicted and may differ on master and the slave.
1723HY000ER_BINLOG_UNSAFE_CREATE_SELECT_AUTOINCCREATE TABLE... SELECT... on a table with an auto-increment column is unsafe because the order in which rows are retrieved by the SELECT determines which (if any) rows are inserted. This order cannot be predicted and may differ on master and the slave.
1724HY000ER_BINLOG_UNSAFE_INSERT_TWO_KEYSINSERT... ON DUPLICATE KEY UPDATE on a table with more than one UNIQUE KEY is unsafe
1725HY000ER_TABLE_IN_FK_CHECKTable is being used in foreign key check.
1726HY000ER_UNSUPPORTED_ENGINEStorage engine '%s' does not support system tables. [%s.%s]
1727HY000ER_BINLOG_UNSAFE_AUTOINC_NOT_FIRSTINSERT into autoincrement field which is not the first part in the composed primary key is unsafe.
1728HY000ER_CANNOT_LOAD_FROM_TABLE_V2Cannot load from %s.%s. The table is probably corrupted
1729HY000ER_MASTER_DELAY_VALUE_OUT_OF_RANGEThe requested value %s for the master delay exceeds the maximum %u
1730HY000ER_ONLY_FD_AND_RBR_EVENTS_ALLOWED_IN_BINLOG_STATEMENTOnly Format_description_log_event and row events are allowed in BINLOG statements (but %s was provided
1731HY000ER_PARTITION_EXCHANGE_DIFFERENT_OPTIONNon matching attribute '%s' between partition and table
1732HY000ER_PARTITION_EXCHANGE_PART_TABLETable to exchange with partition is partitioned: '%s'
1733HY000ER_PARTITION_EXCHANGE_TEMP_TABLETable to exchange with partition is temporary: '%s'
1734HY000ER_PARTITION_INSTEAD_OF_SUBPARTITIONSubpartitioned table, use subpartition instead of partition
1735HY000ER_UNKNOWN_PARTITIONUnknown partition '%s' in table '%s'
1736HY000ER_TABLES_DIFFERENT_METADATATables have different definitions
1737HY000ER_ROW_DOES_NOT_MATCH_PARTITIONFound a row that does not match the partition
1738HY000ER_BINLOG_CACHE_SIZE_GREATER_THAN_MAXOption binlog_cache_size (%lu) is greater than max_binlog_cache_size (%lu); setting binlog_cache_size equal to max_binlog_cache_size.
1739HY000ER_WARN_INDEX_NOT_APPLICABLECannot use %s access on index '%s' due to type or collation conversion on field '%s'
1740HY000ER_PARTITION_EXCHANGE_FOREIGN_KEYTable to exchange with partition has foreign key references: '%s'
1741HY000ER_NO_SUCH_KEY_VALUEKey value '%s' was not found in table '%s.%s'
1742HY000ER_RPL_INFO_DATA_TOO_LONGData for column '%s' too long
1743HY000ER_NETWORK_READ_EVENT_CHECKSUM_FAILUREReplication event checksum verification failed while reading from network.
1744HY000ER_BINLOG_READ_EVENT_CHECKSUM_FAILUREReplication event checksum verification failed while reading from a log file.
1745HY000ER_BINLOG_STMT_CACHE_SIZE_GREATER_THAN_MAXOption binlog_stmt_cache_size (%lu) is greater than max_binlog_stmt_cache_size (%lu); setting binlog_stmt_cache_size equal to max_binlog_stmt_cache_size.
1746HY000ER_CANT_UPDATE_TABLE_IN_CREATE_TABLE_SELECTCan't update table '%s' while '%s' is being created.
1747HY000ER_PARTITION_CLAUSE_ON_NONPARTITIONEDPARTITION () clause on non partitioned table
1748HY000ER_ROW_DOES_NOT_MATCH_GIVEN_PARTITION_SETFound a row not matching the given partition set
1749HY000ER_NO_SUCH_PARTITION_UNUSEDpartition '%s' doesn't exist
1750HY000ER_CHANGE_RPL_INFO_REPOSITORY_FAILUREFailure while changing the type of replication repository: %s.
1751HY000ER_WARNING_NOT_COMPLETE_ROLLBACK_WITH_CREATED_TEMP_TABLEThe creation of some temporary tables could not be rolled back.
1752HY000ER_WARNING_NOT_COMPLETE_ROLLBACK_WITH_DROPPED_TEMP_TABLESome temporary tables were dropped, but these operations could not be rolled back.
1753HY000ER_MTS_FEATURE_IS_NOT_SUPPORTED%s is not supported in multi-threaded slave mode. %s
1754HY000ER_MTS_UPDATED_DBS_GREATER_MAXThe number of modified databases exceeds the maximum %d; the database names will not be included in the replication event metadata.
1755HY000ER_MTS_CANT_PARALLELCannot execute the current event group in the parallel mode. Encountered event %s, relay-log name %s, position %s which prevents execution of this event group in parallel mode. Reason: %s.
1756HY000ER_MTS_INCONSISTENT_DATA%s
1757HY000ER_FULLTEXT_NOT_SUPPORTED_WITH_PARTITIONINGFULLTEXT index is not supported for partitioned tables.
175835000ER_DA_INVALID_CONDITION_NUMBERInvalid condition number
1759HY000ER_INSECURE_PLAIN_TEXTSending passwords in plain text without SSL/TLS is extremely insecure.
1760HY000ER_INSECURE_CHANGE_MASTERStoring MySQL user name or password information in the master info repository is not secure and is therefore not recommended. Please consider using the USER and PASSWORD connection options for START SLAVE; see the 'START SLAVE Syntax' in the MySQL Manual for more information.
176123000ER_FOREIGN_DUPLICATE_KEY_WITH_CHILD_INFOForeign key constraint for table '%s', record '%s' would lead to a duplicate entry in table '%s', key '%s'
176223000ER_FOREIGN_DUPLICATE_KEY_WITHOUT_CHILD_INFOForeign key constraint for table '%s', record '%s' would lead to a duplicate entry in a child table
1763HY000ER_SQLTHREAD_WITH_SECURE_SLAVESetting authentication options is not possible when only the Slave SQL Thread is being started.
1764HY000ER_TABLE_HAS_NO_FTThe table does not have FULLTEXT index to support this query
1765HY000ER_VARIABLE_NOT_SETTABLE_IN_SF_OR_TRIGGERThe system variable %s cannot be set in stored functions or triggers.
1766HY000ER_VARIABLE_NOT_SETTABLE_IN_TRANSACTIONThe system variable %s cannot be set when there is an ongoing transaction.
1767HY000ER_GTID_NEXT_IS_NOT_IN_GTID_NEXT_LISTThe system variable @@SESSION.GTID_NEXT has the value %s, which is not listed in @@SESSION.GTID_NEXT_LIST.
1768HY000ER_CANT_CHANGE_GTID_NEXT_IN_TRANSACTION_WHEN_GTID_NEXT_LIST_IS_NULLThe system variable @@SESSION.GTID_NEXT cannot change inside a transaction.
1769HY000ER_SET_STATEMENT_CANNOT_INVOKE_FUNCTIONThe statement 'SET %s' cannot invoke a stored function.
1770HY000ER_GTID_NEXT_CANT_BE_AUTOMATIC_IF_GTID_NEXT_LIST_IS_NON_NULLThe system variable @@SESSION.GTID_NEXT cannot be 'AUTOMATIC' when @@SESSION.GTID_NEXT_LIST is non-NULL.
1771HY000ER_SKIPPING_LOGGED_TRANSACTIONSkipping transaction %s because it has already been executed and logged.
1772HY000ER_MALFORMED_GTID_SET_SPECIFICATIONMalformed GTID set specification '%s'.
1773HY000ER_MALFORMED_GTID_SET_ENCODINGMalformed GTID set encoding.
1774HY000ER_MALFORMED_GTID_SPECIFICATIONMalformed GTID specification '%s'.
1775HY000ER_GNO_EXHAUSTEDImpossible to generate Global Transaction Identifier: the integer component reached the maximal value. Restart the server with a new server_uuid.
1776HY000ER_BAD_SLAVE_AUTO_POSITIONParameters MASTER_LOG_FILE, MASTER_LOG_POS, RELAY_LOG_FILE and RELAY_LOG_POS cannot be set when MASTER_AUTO_POSITION is active.
1777HY000ER_AUTO_POSITION_REQUIRES_GTID_MODE_ONCHANGE MASTER TO MASTER_AUTO_POSITION = 1 can only be executed when @@GLOBAL.GTID_MODE = ON.
1778HY000ER_CANT_DO_IMPLICIT_COMMIT_IN_TRX_WHEN_GTID_NEXT_IS_SETCannot execute statements with implicit commit inside a transaction when @@SESSION.GTID_NEXT != AUTOMATIC.
1779HY000ER_GTID_MODE_2_OR_3_REQUIRES_DISABLE_GTID_UNSAFE_STATEMENTS_ONGTID_MODE = ON or GTID_MODE = UPGRADE_STEP_2 requires DISABLE_GTID_UNSAFE_STATEMENTS = 1.
1779HY000ER_GTID_MODE_2_OR_3_REQUIRES_ENFORCE_GTID_CONSISTENCY_ON@@GLOBAL.GTID_MODE = ON or UPGRADE_STEP_2 requires @@GLOBAL.ENFORCE_GTID_CONSISTENCY = 1.
1780HY000ER_GTID_MODE_REQUIRES_BINLOG@@GLOBAL.GTID_MODE = ON or UPGRADE_STEP_1 or UPGRADE_STEP_2 requires --log-bin and --log-slave-updates.
1781HY000ER_CANT_SET_GTID_NEXT_TO_GTID_WHEN_GTID_MODE_IS_OFF@@SESSION.GTID_NEXT cannot be set to UUID:NUMBER when @@GLOBAL.GTID_MODE = OFF.
1782HY000ER_CANT_SET_GTID_NEXT_TO_ANONYMOUS_WHEN_GTID_MODE_IS_ON@@SESSION.GTID_NEXT cannot be set to ANONYMOUS when @@GLOBAL.GTID_MODE = ON.
1783HY000ER_CANT_SET_GTID_NEXT_LIST_TO_NON_NULL_WHEN_GTID_MODE_IS_OFF@@SESSION.GTID_NEXT_LIST cannot be set to a non-NULL value when @@GLOBAL.GTID_MODE = OFF.
1784HY000ER_FOUND_GTID_EVENT_WHEN_GTID_MODE_IS_OFFFound a Gtid_log_event or Previous_gtids_log_event when @@GLOBAL.GTID_MODE = OFF.
1785HY000ER_GTID_UNSAFE_NON_TRANSACTIONAL_TABLEWhen @@GLOBAL.ENFORCE_GTID_CONSISTENCY = 1, updates to non-transactional tables can only be done in either autocommitted statements or single-statement transactions, and never in the same statement as updates to transactional tables.
1786HY000ER_GTID_UNSAFE_CREATE_SELECTCREATE TABLE ... SELECT is forbidden when @@GLOBAL.ENFORCE_GTID_CONSISTENCY = 1.
1787HY000ER_GTID_UNSAFE_CREATE_DROP_TEMPORARY_TABLE_IN_TRANSACTIONWhen @@GLOBAL.ENFORCE_GTID_CONSISTENCY = 1, the statements CREATE TEMPORARY TABLE and DROP TEMPORARY TABLE can be executed in a non-transactional context only, and require that AUTOCOMMIT = 1.
1788HY000ER_GTID_MODE_CAN_ONLY_CHANGE_ONE_STEP_AT_A_TIMEThe value of @@GLOBAL.GTID_MODE can only change one step at a time: OFF <-> UPGRADE_STEP_1 <-> UPGRADE_STEP_2 <-> ON. Also note that this value must be stepped up or down simultaneously on all servers; see the Manual for instructions.
1789HY000ER_MASTER_HAS_PURGED_REQUIRED_GTIDSThe slave is connecting using CHANGE MASTER TO MASTER_AUTO_POSITION = 1, but the master has purged binary logs containing GTIDs that the slave requires.
1790HY000ER_CANT_SET_GTID_NEXT_WHEN_OWNING_GTID@@SESSION.GTID_NEXT cannot be changed by a client that owns a GTID. The client owns %s. Ownership is released on COMMIT or ROLLBACK.
1791HY000ER_UNKNOWN_EXPLAIN_FORMATUnknown EXPLAIN format name: '%s'
179225006ER_CANT_EXECUTE_IN_READ_ONLY_TRANSACTIONCannot execute statement in a READ ONLY transaction.
1793HY000ER_TOO_LONG_TABLE_PARTITION_COMMENTComment for table partition '%s' is too long (max = %lu
1794HY000ER_SLAVE_CONFIGURATIONSlave is not configured or failed to initialize properly. You must at least set --server-id to enable either a master or a slave. Additional error messages can be found in the MySQL error log.
1795HY000ER_INNODB_FT_LIMITInnoDB presently supports one FULLTEXT index creation at a time
1796HY000ER_INNODB_NO_FT_TEMP_TABLECannot create FULLTEXT index on temporary InnoDB table
1797HY000ER_INNODB_FT_WRONG_DOCID_COLUMNColumn '%s' is of wrong type for an InnoDB FULLTEXT index
1798HY000ER_INNODB_FT_WRONG_DOCID_INDEXIndex '%s' is of wrong type for an InnoDB FULLTEXT index
1799HY000ER_INNODB_ONLINE_LOG_TOO_BIGCreating index '%s' required more than 'innodb_online_alter_log_max_size' bytes of modification log. Please try again.
Error CodeSQLSTATEErrorDescription
1800HY000ER_UNKNOWN_ALTER_ALGORITHMUnknown ALGORITHM '%s'
1801HY000ER_UNKNOWN_ALTER_LOCKUnknown LOCK type '%s'
1802HY000ER_MTS_CHANGE_MASTER_CANT_RUN_WITH_GAPSCHANGE MASTER cannot be executed when the slave was stopped with an error or killed in MTS mode. Consider using RESET SLAVE or START SLAVE UNTIL.
1803HY000ER_MTS_RECOVERY_FAILURECannot recover after SLAVE errored out in parallel execution mode. Additional error messages can be found in the MySQL error log.
1804HY000ER_MTS_RESET_WORKERSCannot clean up worker info tables. Additional error messages can be found in the MySQL error log.
1805HY000ER_COL_COUNT_DOESNT_MATCH_CORRUPTED_V2Column count of %s.%s is wrong. Expected %d, found %d. The table is probably corrupted
1806HY000ER_SLAVE_SILENT_RETRY_TRANSACTIONSlave must silently retry current transaction
1807HY000ER_DISCARD_FK_CHECKS_RUNNINGThere is a foreign key check running on table '%s'. Cannot discard the table.
1808HY000ER_TABLE_SCHEMA_MISMATCHSchema mismatch (%s
1809HY000ER_TABLE_IN_SYSTEM_TABLESPACETable '%s' in system tablespace
1810HY000ER_IO_READ_ERRORIO Read error: (%lu, %s) %s
1811HY000ER_IO_WRITE_ERRORIO Write error: (%lu, %s) %s
1812HY000ER_TABLESPACE_MISSINGTablespace is missing for table '%s'
1813HY000ER_TABLESPACE_EXISTSTablespace for table '%s' exists. Please DISCARD the tablespace before IMPORT.
1814HY000ER_TABLESPACE_DISCARDEDTablespace has been discarded for table '%s'
1815HY000ER_INTERNAL_ERRORInternal error: %s
1816HY000ER_INNODB_IMPORT_ERRORALTER TABLE '%s' IMPORT TABLESPACE failed with error %lu : '%s'
1817HY000ER_INNODB_INDEX_CORRUPTIndex corrupt: %s
1818HY000ER_INVALID_YEAR_COLUMN_LENGTHYEAR(%lu) column type is deprecated. Creating YEAR(4) column instead.
1819HY000ER_NOT_VALID_PASSWORDYour password does not satisfy the current policy requirements
1820HY000ER_MUST_CHANGE_PASSWORDYou must SET PASSWORD before executing this statement
1821HY000ER_FK_NO_INDEX_CHILDFailed to add the foreign key constaint. Missing index for constraint '%s' in the foreign table '%s'
1822HY000ER_FK_NO_INDEX_PARENTFailed to add the foreign key constaint. Missing index for constraint '%s' in the referenced table '%s'
1823HY000ER_FK_FAIL_ADD_SYSTEMFailed to add the foreign key constraint '%s' to system tables
1824HY000ER_FK_CANNOT_OPEN_PARENTFailed to open the referenced table '%s'
1825HY000ER_FK_INCORRECT_OPTIONFailed to add the foreign key constraint on table '%s'. Incorrect options in FOREIGN KEY constraint '%s'
1826HY000ER_FK_DUP_NAMEDuplicate foreign key constraint name '%s'
1827HY000ER_PASSWORD_FORMATThe password hash doesn't have the expected format. Check if the correct password algorithm is being used with the PASSWORD() function.
1828HY000ER_FK_COLUMN_CANNOT_DROPCannot drop column '%s': needed in a foreign key constraint '%s'
1829HY000ER_FK_COLUMN_CANNOT_DROP_CHILDCannot drop column '%s': needed in a foreign key constraint '%s' of table '%s'
1830HY000ER_FK_COLUMN_NOT_NULLColumn '%s' cannot be NOT NULL: needed in a foreign key constraint '%s' SET NULL
1831HY000ER_DUP_INDEXDuplicate index '%s' defined on the table '%s.%s'. This is deprecated and will be disallowed in a future release.
1832HY000ER_FK_COLUMN_CANNOT_CHANGECannot change column '%s': used in a foreign key constraint '%s'
1833HY000ER_FK_COLUMN_CANNOT_CHANGE_CHILDCannot change column '%s': used in a foreign key constraint '%s' of table '%s'
1834HY000ER_FK_CANNOT_DELETE_PARENTCannot delete rows from table which is parent in a foreign key constraint '%s' of table '%s'
1835HY000ER_MALFORMED_PACKETMalformed communication packet.
1836HY000ER_READ_ONLY_MODERunning in read-only mode
1837HY000ER_GTID_NEXT_TYPE_UNDEFINED_GROUPWhen @@SESSION.GTID_NEXT is set to a GTID, you must explicitly set it to a different value after a COMMIT or ROLLBACK. Please check GTID_NEXT variable manual page for detailed explanation. Current @@SESSION.GTID_NEXT is '%s'.
1838HY000ER_VARIABLE_NOT_SETTABLE_IN_SPThe system variable %s cannot be set in stored procedures.
1839HY000ER_CANT_SET_GTID_PURGED_WHEN_GTID_MODE_IS_OFF@@GLOBAL.GTID_PURGED can only be set when @@GLOBAL.GTID_MODE = ON.
1840HY000ER_CANT_SET_GTID_PURGED_WHEN_GTID_EXECUTED_IS_NOT_EMPTY@@GLOBAL.GTID_PURGED can only be set when @@GLOBAL.GTID_EXECUTED is empty.
1841HY000ER_CANT_SET_GTID_PURGED_WHEN_OWNED_GTIDS_IS_NOT_EMPTY@@GLOBAL.GTID_PURGED can only be set when there are no ongoing transactions (not even in other clients).
1842HY000ER_GTID_PURGED_WAS_CHANGED@@GLOBAL.GTID_PURGED was changed from '%s' to '%s'.
1843HY000ER_GTID_EXECUTED_WAS_CHANGED@@GLOBAL.GTID_EXECUTED was changed from '%s' to '%s'.
1844HY000ER_BINLOG_STMT_MODE_AND_NO_REPL_TABLESCannot execute statement: impossible to write to binary log since BINLOG_FORMAT = STATEMENT, and both replicated and non replicated tables are written to.
18450A000ER_ALTER_OPERATION_NOT_SUPPORTED%s is not supported for this operation. Try %s.
18460A000ER_ALTER_OPERATION_NOT_SUPPORTED_REASON%s is not supported. Reason: %s. Try %s.
1847HY000ER_ALTER_OPERATION_NOT_SUPPORTED_REASON_COPYCOPY algorithm requires a lock
1848HY000ER_ALTER_OPERATION_NOT_SUPPORTED_REASON_PARTITIONPartition specific operations do not yet support LOCK/ALGORITHM
1849HY000ER_ALTER_OPERATION_NOT_SUPPORTED_REASON_FK_RENAMEColumns participating in a foreign key are renamed
1850HY000ER_ALTER_OPERATION_NOT_SUPPORTED_REASON_COLUMN_TYPECannot change column type INPLACE
1851HY000ER_ALTER_OPERATION_NOT_SUPPORTED_REASON_FK_CHECKAdding foreign keys needs foreign_key_checks=OFF
1852HY000ER_ALTER_OPERATION_NOT_SUPPORTED_REASON_IGNORECreating unique indexes with IGNORE requires COPY algorithm to remove duplicate rows
1853HY000ER_ALTER_OPERATION_NOT_SUPPORTED_REASON_NOPKDropping a primary key is not allowed without also adding a new primary key
1854HY000ER_ALTER_OPERATION_NOT_SUPPORTED_REASON_AUTOINCAdding an auto-increment column requires a lock
1855HY000ER_ALTER_OPERATION_NOT_SUPPORTED_REASON_HIDDEN_FTSCannot replace hidden FTS_DOC_ID with a user-visible one
1856HY000ER_ALTER_OPERATION_NOT_SUPPORTED_REASON_CHANGE_FTSCannot drop or rename FTS_DOC_ID
1857HY000ER_ALTER_OPERATION_NOT_SUPPORTED_REASON_FTSFulltext index creation requires a lock
1858HY000ER_SQL_SLAVE_SKIP_COUNTER_NOT_SETTABLE_IN_GTID_MODEsql_slave_skip_counter can not be set when the server is running with @@GLOBAL.GTID_MODE = ON. Instead, for each transaction that you want to skip, generate an empty transaction with the same GTID as the transaction
185923000ER_DUP_UNKNOWN_IN_INDEXDuplicate entry for key '%s'
1860HY000ER_IDENT_CAUSES_TOO_LONG_PATHLong database name and identifier for object resulted in path length exceeding %d characters. Path: '%s'.
1861HY000ER_ALTER_OPERATION_NOT_SUPPORTED_REASON_NOT_NULLcannot silently convert NULL values, as required in this SQL_MODE
1862HY000ER_MUST_CHANGE_PASSWORD_LOGINYour password has expired. To log in you must change it using a client that supports expired passwords.
1863HY000ER_ROW_IN_WRONG_PARTITIONFound a row in wrong partition %s
1864HY000ER_MTS_EVENT_BIGGER_PENDING_JOBS_SIZE_MAXCannot schedule event %s, relay-log name %s, position %s to Worker thread because its size %lu exceeds %lu of slave_pending_jobs_size_max.
1865HY000ER_INNODB_NO_FT_USES_PARSERCannot CREATE FULLTEXT INDEX WITH PARSER on InnoDB table
1866HY000ER_BINLOG_LOGICAL_CORRUPTIONThe binary log file '%s' is logically corrupted: %s
1867HY000ER_WARN_PURGE_LOG_IN_USEfile %s was not purged because it was being read by %d thread(s), purged only %d out of %d files.
1868HY000ER_WARN_PURGE_LOG_IS_ACTIVEfile %s was not purged because it is the active log file.
1869HY000ER_AUTO_INCREMENT_CONFLICTAuto-increment value in UPDATE conflicts with internally generated values
1870HY000WARN_ON_BLOCKHOLE_IN_RBRRow events are not logged for %s statements that modify BLACKHOLE tables in row format. Table(s): '%s'
1871HY000ER_SLAVE_MI_INIT_REPOSITORYSlave failed to initialize master info structure from the repository
1872HY000ER_SLAVE_RLI_INIT_REPOSITORYSlave failed to initialize relay log info structure from the repository
187328000ER_ACCESS_DENIED_CHANGE_USER_ERRORAccess denied trying to change to user '%s'@'%s' (using password: %s). Disconnecting.
1874HY000ER_INNODB_READ_ONLYInnoDB is in read only mode.
1875HY000ER_STOP_SLAVE_SQL_THREAD_TIMEOUTSTOP SLAVE command execution is incomplete: Slave SQL thread got the stop signal, thread is busy, SQL thread will stop once the current task is complete.
1876HY000ER_STOP_SLAVE_IO_THREAD_TIMEOUTSTOP SLAVE command execution is incomplete: Slave IO thread got the stop signal, thread is busy, IO thread will stop once the current task is complete.
1877HY000ER_TABLE_CORRUPTOperation cannot be performed. The table '%s.%s' is missing, corrupt or contains bad data.
1878HY000ER_TEMP_FILE_WRITE_FAILURETemporary file write failure.
1879HY000ER_INNODB_FT_AUX_NOT_HEX_IDUpgrade index name failed, please use create index(alter table) algorithm copy to rebuild index.
1880ER_LAST_MYSQL_ERROR_MESSAGE"

MariaDB-specific error codes

Error CodeSQLSTATEErrorDescription
1900ER_UNUSED_18"
1901ER_GENERATED_COLUMN_FUNCTION_IS_NOT_ALLOWEDFunction or expression '%s' cannot be used in the %s clause of %`s
1902ER_UNUSED_19"
1903ER_PRIMARY_KEY_BASED_ON_GENERATED_COLUMNPrimary key cannot be defined upon a generated column
1904ER_KEY_BASED_ON_GENERATED_VIRTUAL_COLUMNKey/Index cannot be defined on a virtual generated column
1905ER_WRONG_FK_OPTION_FOR_GENERATED_COLUMNCannot define foreign key with %s clause on a generated column
1906ER_WARNING_NON_DEFAULT_VALUE_FOR_GENERATED_COLUMNThe value specified for generated column '%s' in table '%s' has been ignored
1907ER_UNSUPPORTED_ACTION_ON_GENERATED_COLUMNThis is not yet supported for generated columns
1908ER_UNUSED_20"
1909ER_UNUSED_21"
1910ER_UNSUPPORTED_ENGINE_FOR_GENERATED_COLUMNS%s storage engine does not support generated columns
1911ER_UNKNOWN_OPTIONUnknown option '%-.64s'
1912ER_BAD_OPTION_VALUEIncorrect value '%-.64s' for option '%-.64s'
1913ER_UNUSED_6You should never see it
1914ER_UNUSED_7You should never see it
1915ER_UNUSED_8You should never see it
1916ER_DATA_OVERFLOW 22003Got overflow when converting '%-.128s' to %-.32s. Value truncated.
1917ER_DATA_TRUNCATED 22003Truncated value '%-.128s' when converting to %-.32s
1918ER_BAD_DATA 22007Encountered illegal value '%-.128s' when converting to %-.32s
1919ER_DYN_COL_WRONG_FORMATEncountered illegal format of dynamic column string
1920ER_DYN_COL_IMPLEMENTATION_LIMITDynamic column implementation limit reached
1921ER_DYN_COL_DATA 22007Illegal value used as argument of dynamic column function
1922ER_DYN_COL_WRONG_CHARSETDynamic column contains unknown character set
1923ER_ILLEGAL_SUBQUERY_OPTIMIZER_SWITCHESAt least one of the 'in_to_exists' or 'materialization' optimizer_switch flags must be 'on'.
1924ER_QUERY_CACHE_IS_DISABLEDQuery cache is disabled (resize or similar command in progress); repeat this command later
1925ER_QUERY_CACHE_IS_GLOBALY_DISABLEDQuery cache is globally disabled and you can't enable it only for this session
1926ER_VIEW_ORDERBY_IGNOREDView '%-.192s'.'%-.192s' ORDER BY clause ignored because there is other ORDER BY clause already.
1927ER_CONNECTION_KILLED 70100Connection was killed
1928ER_UNUSED_11You should never see it
1929ER_INSIDE_TRANSACTION_PREVENTS_SWITCH_SKIP_REPLICATIONCannot modify @@session.skip_replication inside a transaction
1930ER_STORED_FUNCTION_PREVENTS_SWITCH_SKIP_REPLICATIONCannot modify @@session.skip_replication inside a stored function or trigger
1931ER_QUERY_EXCEEDED_ROWS_EXAMINED_LIMITQuery execution was interrupted. The query examined at least %llu rows, which exceeds LIMIT ROWS EXAMINED (%llu). The query result may be incomplete.
1932ER_NO_SUCH_TABLE_IN_ENGINE 42S02Table '%-.192s.%-.192s' doesn't exist in engine
1933ER_TARGET_NOT_EXPLAINABLETarget is not running an EXPLAINable command
1934ER_CONNECTION_ALREADY_EXISTSConnection '%.*s' conflicts with existing connection '%.*s'
1935ER_MASTER_LOG_PREFIXMaster '%.*s':
1936ER_CANT_START_STOP_SLAVECan't %s SLAVE '%.*s'
1937ER_SLAVE_STARTEDSLAVE '%.*s' started
1938ER_SLAVE_STOPPEDSLAVE '%.*s' stopped
1939ER_SQL_DISCOVER_ERROREngine %s failed to discover table %`-.192s.%`-.192s with '%s'
1940ER_FAILED_GTID_STATE_INITFailed initializing replication GTID state
1941ER_INCORRECT_GTID_STATECould not parse GTID list
1942ER_CANNOT_UPDATE_GTID_STATECould not update replication slave gtid state
1943ER_DUPLICATE_GTID_DOMAINGTID %u-%u-%llu and %u-%u-%llu conflict (duplicate domain id %u)
1944ER_GTID_OPEN_TABLE_FAILEDFailed to open %s.%s
1945ER_GTID_POSITION_NOT_FOUND_IN_BINLOGConnecting slave requested to start from GTID %u-%u-%llu, which is not in the master's binlog
1946ER_CANNOT_LOAD_SLAVE_GTID_STATEFailed to load replication slave GTID position from table %s.%s
1947ER_MASTER_GTID_POS_CONFLICTS_WITH_BINLOGSpecified GTID %u-%u-%llu conflicts with the binary log which contains a more recent GTID %u-%u-%llu. If MASTER_GTID_POS=CURRENT_POS is used, the binlog position will override the new value of @@gtid_slave_pos.
1948ER_MASTER_GTID_POS_MISSING_DOMAINSpecified value for @@gtid_slave_pos contains no value for replication domain %u. This conflicts with the binary log which contains GTID %u-%u-%llu. If MASTER_GTID_POS=CURRENT_POS is used, the binlog position will override the new value of @@gtid_slave_pos.
1949ER_UNTIL_REQUIRES_USING_GTIDSTART SLAVE UNTIL master_gtid_pos requires that slave is using GTID
1950ER_GTID_STRICT_OUT_OF_ORDERAn attempt was made to binlog GTID %u-%u-%llu which would create an out-of-order sequence number with existing GTID %u-%u-%llu, and gtid strict mode is enabled.
1951ER_GTID_START_FROM_BINLOG_HOLEThe binlog on the master is missing the GTID %u-%u-%llu requested by the slave (even though a subsequent sequence number does exist), and GTID strict mode is enabled
1952ER_SLAVE_UNEXPECTED_MASTER_SWITCHUnexpected GTID received from master after reconnect. This normally indicates that the master server was replaced without restarting the slave threads. %s
1953ER_INSIDE_TRANSACTION_PREVENTS_SWITCH_GTID_DOMAIN_ID_SEQ_NOCannot modify @@session.gtid_domain_id or @@session.gtid_seq_no inside a transaction
1954ER_STORED_FUNCTION_PREVENTS_SWITCH_GTID_DOMAIN_ID_SEQ_NOCannot modify @@session.gtid_domain_id or @@session.gtid_seq_no inside a stored function or trigger
1955ER_GTID_POSITION_NOT_FOUND_IN_BINLOG2Connecting slave requested to start from GTID %u-%u-%llu, which is not in the master's binlog. Since the master's binlog contains GTIDs with higher sequence numbers, it probably means that the slave has diverged due to executing extra errorneous transactions
1956ER_BINLOG_MUST_BE_EMPTYThis operation is not allowed if any GTID has been logged to the binary log. Run RESET MASTER first to erase the log
1957ER_NO_SUCH_QUERYUnknown query id: %lld
1958ER_BAD_BASE64_DATABad base64 data as position %u
1959ER_INVALID_ROLEInvalid role specification %`s.
1960ER_INVALID_CURRENT_USERThe current user is invalid.
1961ER_CANNOT_GRANT_ROLECannot grant role '%s' to: %s.
1962ER_CANNOT_REVOKE_ROLECannot revoke role '%s' from: %s.
1963ER_CHANGE_SLAVE_PARALLEL_THREADS_ACTIVECannot change @@slave_parallel_threads while another change is in progress
1964ER_PRIOR_COMMIT_FAILEDCommit failed due to failure of an earlier commit on which this one depends
1965ER_IT_IS_A_VIEW'%-.192s' is a view
1966ER_SLAVE_SKIP_NOT_IN_GTIDWhen using GTID, @@sql_slave_skip_counter can not be used. Instead, setting @@gtid_slave_pos explicitly can be used to skip to after a given GTID position.
1967ER_TABLE_DEFINITION_TOO_BIGThe definition for table %`s is too big
1968ER_PLUGIN_INSTALLEDPlugin '%-.192s' already installed
1969ER_STATEMENT_TIMEOUTQuery execution was interrupted (max_statement_time exceeded)
1970ER_SUBQUERIES_NOT_SUPPORTED%s does not support subqueries or stored functions.
1971ER_SET_STATEMENT_NOT_SUPPORTEDThe system variable %.200s cannot be set in SET STATEMENT.
1972ER_UNUSED_9You should never see it
1973ER_USER_CREATE_EXISTSCan't create user '%-.64s'@'%-.64s'; it already exists
1974ER_USER_DROP_EXISTSCan't drop user '%-.64s'@'%-.64s'; it doesn't exist
1975ER_ROLE_CREATE_EXISTSCan't create role '%-.64s'; it already exists
1976ER_ROLE_DROP_EXISTSCan't drop role '%-.64s'; it doesn't exist
1977ER_CANNOT_CONVERT_CHARACTERCannot convert '%s' character 0x%-.64s to '%s'
1978ER_INVALID_DEFAULT_VALUE_FOR_FIELDIncorrect default value '%-.128s' for column '%.192s'
1979ER_KILL_QUERY_DENIED_ERRORYou are not owner of query %lu
1980ER_NO_EIS_FOR_FIELDEngine-independent statistics are not collected for column '%s'
1981ER_WARN_AGGFUNC_DEPENDENCEAggregate function '%-.192s)' of SELECT #%d belongs to SELECT #%d
1982WARN_INNODB_PARTITION_OPTION_IGNORED<%-.64s> option ignored for InnoDB partition
Error CodeSQLSTATEErrorDescription
3000ER_FILE_CORRUPTFile %s is corrupted
3001ER_ERROR_ON_MASTERQuery partially completed on the master (error on master: %d) and was aborted. There is a chance that your master is inconsistent at this point. If you are sure that your master is ok, run this query manually on the slave and then restart the slave with SET GLOBAL SQL_SLAVE_SKIP_COUNTER=1; START SLAVE;. Query:'%s'"
3002ER_INCONSISTENT_ERRORQuery caused different errors on master and slave. Error on master: message (format)='%s' error code=%d; Error on slave:actual message='%s', error code=%d. Default database:'%s'. Query:'%s'
3003ER_STORAGE_ENGINE_NOT_LOADEDStorage engine for table '%s'.'%s' is not loaded.
3004ER_GET_STACKED_DA_WITHOUT_ACTIVE_HANDLER 0Z002GET STACKED DIAGNOSTICS when handler not active
3005ER_WARN_LEGACY_SYNTAX_CONVERTED%s is no longer supported. The statement was converted to %s.
3006ER_BINLOG_UNSAFE_FULLTEXT_PLUGINStatement is unsafe because it uses a fulltext parser plugin which may not return the same value on the slave.
3007ER_CANNOT_DISCARD_TEMPORARY_TABLECannot DISCARD/IMPORT tablespace associated with temporary table
3008ER_FK_DEPTH_EXCEEDEDForeign key cascade delete/update exceeds max depth of %d.
3009ER_COL_COUNT_DOESNT_MATCH_PLEASE_UPDATE_V2Column count of %s.%s is wrong. Expected %d, found %d. Created with MariaDB %d, now running %d. Please use mysql_upgrade to fix this error.
3010ER_WARN_TRIGGER_DOESNT_HAVE_CREATEDTrigger %s.%s.%s does not have CREATED attribute.
3011ER_REFERENCED_TRG_DOES_NOT_EXIST_MYSQLReferenced trigger '%s' for the given action time and event type does not exist.
3012ER_EXPLAIN_NOT_SUPPORTEDEXPLAIN FOR CONNECTION command is supported only for SELECT/UPDATE/INSERT/DELETE/REPLACE
3013ER_INVALID_FIELD_SIZEInvalid size for column '%-.192s'.
3014ER_MISSING_HA_CREATE_OPTIONTable storage engine '%-.64s' found required create option missing
3015ER_ENGINE_OUT_OF_MEMORYOut of memory in storage engine '%-.64s'.
3016ER_PASSWORD_EXPIRE_ANONYMOUS_USERThe password for anonymous user cannot be expired.
3017ER_SLAVE_SQL_THREAD_MUST_STOPThis operation cannot be performed with a running slave sql thread; run STOP SLAVE SQL_THREAD first
3018ER_NO_FT_MATERIALIZED_SUBQUERYCannot create FULLTEXT index on materialized subquery
3019ER_INNODB_UNDO_LOG_FULLUndo Log error: %s
3020ER_INVALID_ARGUMENT_FOR_LOGARITHMInvalid argument for logarithm
3021ER_SLAVE_CHANNEL_IO_THREAD_MUST_STOPThis operation cannot be performed with a running slave io thread; run STOP SLAVE IO_THREAD FOR CHANNEL '%s' first.
3022ER_WARN_OPEN_TEMP_TABLES_MUST_BE_ZEROThis operation may not be safe when the slave has temporary tables. The tables will be kept open until the server restarts or until the tables are deleted by any replicated DROP statement. Suggest to wait until slave_open_temp_tables = 0.
3023ER_WARN_ONLY_MASTER_LOG_FILE_NO_POSCHANGE MASTER TO with a MASTER_LOG_FILE clause but no MASTER_LOG_POS clause may not be safe. The old position value may not be valid for the new binary log file.
3024ER_QUERY_TIMEOUTQuery execution was interrupted, maximum statement execution time exceeded
3025ER_NON_RO_SELECT_DISABLE_TIMERSelect is not a read only statement, disabling timer
3026ER_DUP_LIST_ENTRYDuplicate entry '%-.192s'.
3027ER_SQL_MODE_NO_EFFECT'%s' mode no longer has any effect. Use STRICT_ALL_TABLES or STRICT_TRANS_TABLES instead.
3028ER_AGGREGATE_ORDER_FOR_UNIONExpression #%u of ORDER BY contains aggregate function and applies to a UNION
3029ER_AGGREGATE_ORDER_NON_AGG_QUERYExpression #%u of ORDER BY contains aggregate function and applies to the result of a non-aggregated query
3030ER_SLAVE_WORKER_STOPPED_PREVIOUS_THD_ERRORSlave worker has stopped after at least one previous worker encountered an error when slave-preserve-commit-order was enabled. To preserve commit order, the last transaction executed by this thread has not been committed. When restarting the slave after fixing any failed threads, you should fix this worker as well.
3031ER_DONT_SUPPORT_SLAVE_PRESERVE_COMMIT_ORDERslave_preserve_commit_order is not supported %s.
3032ER_SERVER_OFFLINE_MODEThe server is currently in offline mode
3033ER_GIS_DIFFERENT_SRIDSBinary geometry function %s given two geometries of different srids: %u and %u, which should have been identical.
3034ER_GIS_UNSUPPORTED_ARGUMENTCalling geometry function %s with unsupported types of arguments.
3035ER_GIS_UNKNOWN_ERRORUnknown GIS error occurred in function %s.
3036ER_GIS_UNKNOWN_EXCEPTIONUnknown exception caught in GIS function %s.
3037ER_GIS_INVALID_DATAInvalid GIS data provided to function %s.
3038ER_BOOST_GEOMETRY_EMPTY_INPUT_EXCEPTIONThe geometry has no data in function %s.
3039ER_BOOST_GEOMETRY_CENTROID_EXCEPTIONUnable to calculate centroid because geometry is empty in function %s.
3040ER_BOOST_GEOMETRY_OVERLAY_INVALID_INPUT_EXCEPTIONGeometry overlay calculation error: geometry data is invalid in function %s.
3041ER_BOOST_GEOMETRY_TURN_INFO_EXCEPTIONGeometry turn info calculation error: geometry data is invalid in function %s.
3042ER_BOOST_GEOMETRY_SELF_INTERSECTION_POINT_EXCEPTIONAnalysis procedures of intersection points interrupted unexpectedly in function %s.
3043ER_BOOST_GEOMETRY_UNKNOWN_EXCEPTIONUnknown exception thrown in function %s.
3044ER_STD_BAD_ALLOC_ERRORMemory allocation error: %-.256s in function %s.
3045ER_STD_DOMAIN_ERRORDomain error: %-.256s in function %s.
3046ER_STD_LENGTH_ERRORLength error: %-.256s in function %s.
3047ER_STD_INVALID_ARGUMENTInvalid argument error: %-.256s in function %s.
3048ER_STD_OUT_OF_RANGE_ERROROut of range error: %-.256s in function %s.
3049ER_STD_OVERFLOW_ERROROverflow error error: %-.256s in function %s.
3050ER_STD_RANGE_ERRORRange error: %-.256s in function %s.
3051ER_STD_UNDERFLOW_ERRORUnderflow error: %-.256s in function %s.
3052ER_STD_LOGIC_ERRORLogic error: %-.256s in function %s.
3053ER_STD_RUNTIME_ERRORRuntime error: %-.256s in function %s.
3054ER_STD_UNKNOWN_EXCEPTIONUnknown exception: %-.384s in function %s.
3055ER_GIS_DATA_WRONG_ENDIANESSGeometry byte string must be little endian.
3056ER_CHANGE_MASTER_PASSWORD_LENGTHThe password provided for the replication user exceeds the maximum length of 32 characters
305742000ER_USER_LOCK_WRONG_NAMEIncorrect user-level lock name '%-.192s'.
3058ER_USER_LOCK_DEADLOCKDeadlock found when trying to get user-level lock; try rolling back transaction/releasing locks and restarting lock acquisition.
3059ER_REPLACE_INACCESSIBLE_ROWSREPLACE cannot be executed as it requires deleting rows that are not in the view
3060ER_ALTER_OPERATION_NOT_SUPPORTED_REASON_GISDo not support online operation on table with GIS index
Error CodeSQLSTATEErrorDescription
40000A000ER_COMMULTI_BADCONTEXTCOM_MULTI can't return a result set in the given context
4001ER_BAD_COMMAND_IN_MULTICommand '%s' is not allowed for COM_MULTI
4002ER_WITH_COL_WRONG_LISTWITH column list and SELECT field list have different column counts
4003ER_TOO_MANY_DEFINITIONS_IN_WITH_CLAUSEToo many WITH elements in WITH clause
4004ER_DUP_QUERY_NAMEDuplicate query name %`-.64s in WITH clause
4005ER_RECURSIVE_WITHOUT_ANCHORSNo anchors for recursive WITH element '%s'
4006ER_UNACCEPTABLE_MUTUAL_RECURSIONUnacceptable mutual recursion with anchored table '%s'
4007ER_REF_TO_RECURSIVE_WITH_TABLE_IN_DERIVEDReference to recursive WITH table '%s' in materialized derived
4008ER_NOT_STANDARD_COMPLIANT_RECURSIVERestrictions imposed on recursive definitions are violated for table '%s'"R_WRONG_WINDOW_SPEC_NAME
4009ER_WRONG_WINDOW_SPEC_NAMEWindow specification with name '%s' is not defined
4010ER_DUP_WINDOW_NAMEMultiple window specifications with the same name '%s'
4011ER_PARTITION_LIST_IN_REFERENCING_WINDOW_SPECWindow specification referencing another one '%s' cannot contain partition list
4012ER_ORDER_LIST_IN_REFERENCING_WINDOW_SPECReferenced window specification '%s' already contains order list
4013ER_WINDOW_FRAME_IN_REFERENCED_WINDOW_SPECReferenced window specification '%s' cannot contain window frame
4014ER_BAD_COMBINATION_OF_WINDOW_FRAME_BOUND_SPECSUnacceptable combination of window frame bound specifications
4015ER_WRONG_PLACEMENT_OF_WINDOW_FUNCTIONWindow function is allowed only in SELECT list and ORDER BY clause
4016ER_WINDOW_FUNCTION_IN_WINDOW_SPECWindow function is not allowed in window specification
4017ER_NOT_ALLOWED_WINDOW_FRAMEWindow frame is not allowed with '%s'
4018ER_NO_ORDER_LIST_IN_WINDOW_SPECNo order list in window specification for '%s'
4019ER_RANGE_FRAME_NEEDS_SIMPLE_ORDERBYRANGE-type frame requires ORDER BY clause with single sort key
4020ER_WRONG_TYPE_FOR_ROWS_FRAMEInteger is required for ROWS-type frame
4021ER_WRONG_TYPE_FOR_RANGE_FRAMENumeric datatype is required for RANGE-type frame
4022ER_FRAME_EXCLUSION_NOT_SUPPORTEDFrame exclusion is not supported yet
4023ER_WINDOW_FUNCTION_DONT_HAVE_FRAMEThis window function may not have a window frame
4024ER_INVALID_NTILE_ARGUMENTArgument of NTILE must be greater than 0
402523000ER_CONSTRAINT_FAILEDCONSTRAINT %`s failed for %`-.192s.%`-.192s
4026ER_EXPRESSION_IS_TOO_BIGExpression in the %s clause is too big
4027ER_ERROR_EVALUATING_EXPRESSIONGot an error evaluating stored expression %s
4028ER_CALCULATING_DEFAULT_VALUEGot an error when calculating default value for %`s
4029ER_EXPRESSION_REFERS_TO_UNINIT_FIELDExpression for field %`-.64s is referring to uninitialized field %`s
4030ER_PARTITION_DEFAULT_ERROROnly one DEFAULT partition allowed
4031ER_REFERENCED_TRG_DOES_NOT_EXISTReferenced trigger '%s' for the given action time and event type does not exist
4032ER_INVALID_DEFAULT_PARAMDefault/ignore value is not supported for such parameter usage
4033ER_BINLOG_NON_SUPPORTED_BULKOnly row based replication supported for bulk operations
4034ER_BINLOG_UNCOMPRESS_ERRORUncompress the compressed binlog failed
4035ER_JSON_BAD_CHRBroken JSON string in argument %d to function '%s' at position %d
4036ER_JSON_NOT_JSON_CHRCharacter disallowed in JSON in argument %d to function '%s' at position %d
4037ER_JSON_EOSUnexpected end of JSON text in argument %d to function '%s'
4038ER_JSON_SYNTAXSyntax error in JSON text in argument %d to function '%s' at position %d
4039ER_JSON_ESCAPINGIncorrect escaping in JSON text in argument %d to function '%s' at position %d
4040ER_JSON_DEPTHLimit of %d on JSON nested strucures depth is reached in argument %d to function '%s' at position %d
4041ER_JSON_PATH_EOSUnexpected end of JSON path in argument %d to function '%s'
4042ER_JSON_PATH_SYNTAXSyntax error in JSON path in argument %d to function '%s' at position %d
4043ER_JSON_PATH_DEPTHLimit of %d on JSON path depth is reached in argument %d to function '%s' at position %d
4044ER_JSON_PATH_NO_WILDCARDWildcards in JSON path not allowed in argument %d to function '%s'
4045ER_JSON_PATH_ARRAYJSON path should end with an array identifier in argument %d to function '%s'
4046ER_JSON_ONE_OR_ALLArgument 2 to function '%s' must be "one" or "all".
4047ER_UNSUPPORT_COMPRESSED_TEMPORARY_TABLECREATE TEMPORARY TABLE is not allowed with ROW_FORMAT=COMPRESSED or KEY_BLOCK_SIZE.
4048ER_GEOJSON_INCORRECTIncorrect GeoJSON format specified for st_geomfromgeojson function.
4049ER_GEOJSON_TOO_FEW_POINTSIncorrect GeoJSON format - too few points for linestring specified.
4050ER_GEOJSON_NOT_CLOSEDIncorrect GeoJSON format - polygon not closed.
4051ER_JSON_PATH_EMPTYPath expression '$' is not allowed in argument %d to function '%s'.
4052ER_SLAVE_SAME_IDA slave with the same server_uuid/server_id as this slave has connected to the master
4053ER_FLASHBACK_NOT_SUPPORTEDFlashback does not support %s %s
4054ER_KEYS_OUT_OF_ORDERKeys are out order during bulk load
4055ER_OVERLAPPING_KEYSBulk load rows overlap existing rows
4056ER_REQUIRE_ROW_BINLOG_FORMATCan't execute updates on master with binlog_format != ROW.
4057ER_ISOLATION_MODE_NOT_SUPPORTEDMyRocks supports only READ COMMITTED and REPEATABLE READ isolation levels. Please change from current isolation level %s
4058ER_ON_DUPLICATE_DISABLEDWhen unique checking is disabled in MyRocks, INSERT,UPDATE,LOAD statements with clauses that update or replace the key (i.e. INSERT ON DUPLICATE KEY UPDATE, REPLACE) are not allowed. Query: %s
4059ER_UPDATES_WITH_CONSISTENT_SNAPSHOTCan't execute updates when you started a transaction with START TRANSACTION WITH CONSISTENT [ROCKSDB] SNAPSHOT.
4060ER_ROLLBACK_ONLYThis transaction was rolled back and cannot be committed. Only supported operation is to roll it back, so all pending changes will be discarded. Please restart another transaction.
4061ER_ROLLBACK_TO_SAVEPOINTMyRocks currently does not support ROLLBACK TO SAVEPOINT if modifying rows.
4062ER_ISOLATION_LEVEL_WITH_CONSISTENT_SNAPSHOTOnly REPEATABLE READ isolation level is supported for START TRANSACTION WITH CONSISTENT SNAPSHOT in RocksDB Storage Engine.
4063ER_UNSUPPORTED_COLLATIONUnsupported collation on string indexed column %s.%s Use binary collation (%s).
4064ER_METADATA_INCONSISTENCYTable '%s' does not exist, but metadata information exists inside MyRocks. This is a sign of data inconsistency. Please check if '%s.frm' exists, and try to restore it if it does not exist.
4065ER_CF_DIFFERENTColumn family ('%s') flag (%d) is different from an existing flag (%d). Assign a new CF flag, or do not change existing CF flag.
4066ER_RDB_TTL_DURATION_FORMATTTL duration (%s) in MyRocks must be an unsigned non-null 64-bit integer.
4067ER_RDB_STATUS_GENERALStatus error %d received from RocksDB: %s
4068ER_RDB_STATUS_MSG%s, Status error %d received from RocksDB: %s
4069ER_RDB_TTL_UNSUPPORTEDTTL support is currently disabled when table has a hidden PK.
4070ER_RDB_TTL_COL_FORMATTTL column (%s) in MyRocks must be an unsigned non-null 64-bit integer, exist inside the table, and have an accompanying ttl duration.
4071ER_PER_INDEX_CF_DEPRECATEDThe per-index column family option has been deprecated
4072ER_KEY_CREATE_DURING_ALTERMyRocks failed creating new key definitions during alter.
4073ER_SK_POPULATE_DURING_ALTERMyRocks failed populating secondary key during alter.
4074ER_SUM_FUNC_WITH_WINDOW_FUNC_AS_ARGWindow functions can not be used as arguments to group functions.
4075ER_NET_OK_PACKET_TOO_LARGEOK packet too large
4076ER_GEOJSON_EMPTY_COORDINATESIncorrect GeoJSON format - empty 'coordinates' array.
4077ER_MYROCKS_CANT_NOPAD_COLLATIONMyRocks doesn't currently support collations with \"No pad\" attribute.
4078ER_ILLEGAL_PARAMETER_DATA_TYPES2_FOR_OPERATIONIllegal parameter data types %s and %s for operation '%s'
4079ER_ILLEGAL_PARAMETER_DATA_TYPE_FOR_OPERATIONIllegal parameter data type %s for operation '%s'
4080ER_WRONG_PARAMCOUNT_TO_CURSORIncorrect parameter count to cursor '%-.192s'
4081ER_UNKNOWN_STRUCTURED_VARIABLEUnknown structured system variable or ROW routine variable '%-.*s'
4082ER_ROW_VARIABLE_DOES_NOT_HAVE_FIELDRow variable '%-.192s' does not have a field '%-.192s'
4083ER_END_IDENTIFIER_DOES_NOT_MATCHEND identifier '%-.192s' does not match '%-.192s'
4084ER_SEQUENCE_RUN_OUTSequence '%-.64s.%-.64s' has run out
4085ER_SEQUENCE_INVALID_DATASequence '%-.64s.%-.64s' values are conflicting
4086ER_SEQUENCE_INVALID_TABLE_STRUCTURESequence '%-.64s.%-.64s' table structure is invalid (%s)
4087ER_SEQUENCE_ACCESS_ERRORSequence '%-.64s.%-.64s' access error
4088ER_SEQUENCE_BINLOG_FORMATSequences requires binlog_format mixed or row
4089ER_NOT_SEQUENCE'%-.64s.%-.64s' is not a SEQUENCE
4090ER_NOT_SEQUENCE2'%-.192s' is not a SEQUENCE
4091ER_UNKNOWN_SEQUENCESUnknown SEQUENCE: '%-.300s'
4092ER_UNKNOWN_VIEWUnknown VIEW: '%-.300s'
4093ER_WRONG_INSERT_INTO_SEQUENCEWrong INSERT into a SEQUENCE. One can only do single table INSERT into a sequence object (like with mysqldump). If you want to change the SEQUENCE, use ALTER SEQUENCE instead.
4094ER_SP_STACK_TRACEAt line %u in %s
4095ER_PACKAGE_ROUTINE_IN_SPEC_NOT_DEFINED_IN_BODYSubroutine '%-.192s' is declared in the package specification but is not defined in the package body
4096ER_PACKAGE_ROUTINE_FORWARD_DECLARATION_NOT_DEFINEDSubroutine '%-.192s' has a forward declaration but is not defined
4097ER_COMPRESSED_COLUMN_USED_AS_KEYCompressed column '%-.192s' can't be used in key specification
4098ER_UNKNOWN_COMPRESSION_METHODUnknown compression method: %s
4099ER_WRONG_NUMBER_OF_VALUES_IN_TVCThe used table value constructor has a different number of values
4100ER_FIELD_REFERENCE_IN_TVCField reference '%-.192s' can't be used in table value constructor
4101ER_WRONG_TYPE_FOR_PERCENTILE_FUNCNumeric datatype is required for %s function
4102ER_ARGUMENT_NOT_CONSTANTArgument to the %s function is not a constant for a partition
4103ER_ARGUMENT_OUT_OF_RANGEArgument to the %s function does not belong to the range [0,1]
4104ER_WRONG_TYPE_OF_ARGUMENT%s function only accepts arguments that can be converted to numerical types
4105ER_NOT_AGGREGATE_FUNCTIONAggregate specific instruction (FETCH GROUP NEXT ROW) used in a wrong context
4106ER_INVALID_AGGREGATE_FUNCTIONAggregate specific instruction(FETCH GROUP NEXT ROW) missing from the aggregate function
4107ER_INVALID_VALUE_TO_LIMITLimit only accepts integer values
4108ER_INVISIBLE_NOT_NULL_WITHOUT_DEFAULTInvisible column %`s must have a default value
4109ER_UPDATE_INFO_WITH_SYSTEM_VERSIONINGRows matched: %ld Changed: %ld Inserted: %ld Warnings: %ld
4110ER_VERS_FIELD_WRONG_TYPE%`s must be of type %s for system-versioned table %`s
4111ER_VERS_ENGINE_UNSUPPORTEDTransaction-precise system versioning for %`s is not supported
4112ER_UNUSED_23You should never see it
4113ER_PARTITION_WRONG_TYPEWrong partitioning type, expected type: %`s
4114WARN_VERS_PART_FULLVersioned table %`s.%`s: last HISTORY partition (%`s) is out of %s, need more HISTORY partitions
4115WARN_VERS_PARAMETERSMaybe missing parameters: %s
4116ER_VERS_DROP_PARTITION_INTERVALCan only drop oldest partitions when rotating by INTERVAL
4117ER_UNUSED_25You should never see it
4118WARN_VERS_PART_NON_HISTORICALPartition %`s contains non-historical data
4119ER_VERS_ALTER_NOT_ALLOWEDNot allowed for system-versioned %`s.%`s. Change @@system_versioning_alter_history to proceed with ALTER.
4120ER_VERS_ALTER_ENGINE_PROHIBITEDNot allowed for system-versioned %`s.%`s. Change to/from native system versioning engine is not supported.
4121ER_VERS_RANGE_PROHIBITEDSYSTEM_TIME range selector is not allowed
4122ER_CONFLICTING_FOR_SYSTEM_TIMEConflicting FOR SYSTEM_TIME clauses in WITH RECURSIVE
4123ER_VERS_TABLE_MUST_HAVE_COLUMNSTable %`s must have at least one versioned column
4124ER_VERS_NOT_VERSIONEDTable %`s is not system-versioned
4125ER_MISSINGWrong parameters for %`s: missing '%s'
4126ER_VERS_PERIOD_COLUMNSPERIOD FOR SYSTEM_TIME must use columns %`s and %`s
4127ER_PART_WRONG_VALUEWrong parameters for partitioned %`s: wrong value for '%s'
4128ER_VERS_WRONG_PARTSWrong partitions for %`s: must have at least one HISTORY and exactly one last CURRENT
4129ER_VERS_NO_TRX_IDTRX_ID %llu not found in `mysql.transaction_registry`
4130ER_VERS_ALTER_SYSTEM_FIELDCan not change system versioning field %`s
4131ER_DROP_VERSIONING_SYSTEM_TIME_PARTITIONCan not DROP SYSTEM VERSIONING for table %`s partitioned BY SYSTEM_TIME
4132ER_VERS_DB_NOT_SUPPORTEDSystem-versioned tables in the %`s database are not supported
4133ER_VERS_TRT_IS_DISABLEDTransaction registry is disabled
4134ER_VERS_DUPLICATE_ROW_START_ENDDuplicate ROW %s column %`s
4135ER_VERS_ALREADY_VERSIONEDTable %`s is already system-versioned
4136ER_UNUSED_24You should never see it
4137ER_VERS_NOT_SUPPORTEDSystem-versioned tables do not support %s
4138ER_VERS_TRX_PART_HISTORIC_ROW_NOT_SUPPORTEDTransaction-precise system-versioned tables do not support partitioning by ROW START or ROW END
4139ER_INDEX_FILE_FULLThe index file for table '%-.192s' is full
4140ER_UPDATED_COLUMN_ONLY_ONCEThe column %`s.%`s cannot be changed more than once in a single UPDATE statement
4141ER_EMPTY_ROW_IN_TVCRow with no elements is not allowed in table value constructor in this context
4142ER_VERS_QUERY_IN_PARTITIONSYSTEM_TIME partitions in table %`s does not support historical query
4143ER_KEY_DOESNT_SUPPORT%s index %`s does not support this operation
4144ER_ALTER_OPERATION_TABLE_OPTIONS_NEED_REBUILDChanging table options requires the table to be rebuilt
4145ER_BACKUP_LOCK_IS_ACTIVECan't execute the command as you have a BACKUP STAGE active
4146ER_BACKUP_NOT_RUNNINGYou must start backup with \"BACKUP STAGE START\"
4147ER_BACKUP_WRONG_STAGEBackup stage '%s' is same or before current backup stage '%s'
4148ER_BACKUP_STAGE_FAILEDBackup stage '%s' failed
4149ER_BACKUP_UNKNOWN_STAGEUnknown backup stage: '%s'. Stage should be one of START, FLUSH, BLOCK_DDL, BLOCK_COMMIT or END
4150ER_USER_IS_BLOCKEDUser is blocked because of too many credential errors; unblock with 'FLUSH PRIVILEGES'
4151ER_ACCOUNT_HAS_BEEN_LOCKEDAccess denied, this account is locked
4152ER_PERIOD_TEMPORARY_NOT_ALLOWEDApplication-time period table cannot be temporary
4153ER_PERIOD_TYPES_MISMATCHFields of PERIOD FOR %`s have different types
4154ER_MORE_THAN_ONE_PERIODCannot specify more than one application-time period
4155ER_PERIOD_FIELD_WRONG_ATTRIBUTESPeriod field %`s cannot be %s
4156ER_PERIOD_NOT_FOUNDPeriod %`s is not found in table
4157ER_PERIOD_COLUMNS_UPDATEDColumn %`s used in period %`s specified in update SET list
4158ER_PERIOD_CONSTRAINT_DROPCan't DROP CONSTRAINT `%s`. Use DROP PERIOD `%s` for this
415942000 S1009ER_TOO_LONG_KEYPARTSpecified key part was too long; max key part length is %u bytes
4160ER_TOO_LONG_DATABASE_COMMENTComment for database '%-.64s' is too long (max = %u)
4161ER_UNKNOWN_DATA_TYPEUnknown data type: '%-.64s'
4162ER_UNKNOWN_OPERATOROperator does not exists: '%-.128s'
4163ER_WARN_HISTORY_ROW_START_TIMETable `%s.%s` history row start '%s' is later than row end '%s'
4164ER_PART_STARTS_BEYOND_INTERVAL%`s: STARTS is later than query time, first history partition may exceed INTERVAL value
4165ER_GALERA_REPLICATION_NOT_SUPPORTEDDDL-statement is forbidden as table storage engine does not support Galera replication
4166HY000ER_LOAD_INFILE_CAPABILITY_DISABLEDThe used command is not allowed because the MariaDB server or client has disabled the local infile capability
4167ER_NO_SECURE_TRANSPORTS_CONFIGUREDNo secure transports are configured, unable to set --require_secure_transport=ON
4168ER_SLAVE_IGNORED_SHARED_TABLESlave SQL thread ignored the '%s' because table is shared
4169ER_NO_AUTOINCREMENT_WITH_UNIQUEAUTO_INCREMENT column %`s cannot be used in the UNIQUE index %`s
4170ER_KEY_CONTAINS_PERIOD_FIELDSKey %`s cannot explicitly include column %`s
4171ER_KEY_CANT_HAVE_WITHOUT_OVERLAPSKey %`s cannot have WITHOUT OVERLAPS
4172ER_NOT_ALLOWED_IN_THIS_CONTEXT'%-.128s' is not allowed in this context
4173ER_DATA_WAS_COMMITED_UNDER_ROLLBACKEngine %s does not support rollback. Changes where commited during rollback call
4174ER_PK_INDEX_CANT_BE_IGNOREDA primary key cannot be marked as IGNORE
4175ER_BINLOG_UNSAFE_SKIP_LOCKEDSKIP LOCKED makes this statement unsafe
4176ER_JSON_TABLE_ERROR_ON_FIELDField '%s' can't be set for JSON_TABLE '%s'.
4177ER_JSON_TABLE_ALIAS_REQUIREDEvery table function must have an alias.
4178ER_JSON_TABLE_SCALAR_EXPECTEDCan't store an array or an object in the scalar column '%s' of JSON_TABLE '%s'.
4179ER_JSON_TABLE_MULTIPLE_MATCHESCan't store multiple matches of the path in the column '%s' of JSON_TABLE '%s'.
4180ER_WITH_TIES_NEEDS_ORDERFETCH ... WITH TIES requires ORDER BY clause to be present
4181ER_REMOVED_ORPHAN_TRIGGERDropped orphan trigger '%-.64s', originally created for table: '%-.192s'
4182ER_STORAGE_ENGINE_DISABLEDStorage engine %s is disabled

1.1.2.10 Numeric Literals

Numeric literals are written as a sequence of digits from 0 to 9. Initial zeros are ignored. A sign can always precede the digits, but it is optional for positive numbers. In decimal numbers, the integer part and the decimal part are divided with a dot (.).

If the integer part is zero, it can be omitted, but the literal must begin with a dot.

The notation with exponent can be used. The exponent is preceded by an E or e character. The exponent can be preceded by a sign and must be an integer. A number N with an exponent part X, is calculated as N * POW(10, X).

In some cases, adding zeroes at the end of a decimal number can increment the precision of the expression where the number is used. For example, PI() by default returns a number with 6 decimal digits. But the PI()+0.0000000000 expression (with 10 zeroes) returns a number with 10 decimal digits.

Hexadecimal literals are interpreted as numbers when used in numeric contexts.

Examples

10
+10
-10

All these literals are equivalent:

0.1
.1
+0.1
+.1

With exponents:

0.2E3 -- 0.2 * POW(10, 3) = 200
.2e3
.2e+2
1.1e-10 -- 0.00000000011
-1.1e10 -- -11000000000

1.1.2.11 Reserved Words

Contents

  1. Reserved Words
  2. Exceptions
  3. Oracle Mode
  4. Function Names
  5. See Also

The following is a list of all reserved words in MariaDB.

Reserved words cannot be used as Identifiers, unless they are quoted.

The definitive list of reserved words for each version can be found by examining the sql/lex.h and sql/sql_yacc.yy files.

Reserved Words

KeywordNotes
ACCESSIBLE
ADD
ALL
ALTER
ANALYZE
AND
AS
ASC
ASENSITIVE
BEFORE
BETWEEN
BIGINT
BINARY
BLOB
BOTH
BY
CALL
CASCADE
CASE
CHANGE
CHAR
CHARACTER
CHECK
COLLATE
COLUMN
CONDITION
CONSTRAINT
CONTINUE
CONVERT
CREATE
CROSS
CURRENT_DATE
CURRENT_ROLE
CURRENT_TIME
CURRENT_TIMESTAMP
CURRENT_USER
CURSOR
DATABASE
DATABASES
DAY_HOUR
DAY_MICROSECOND
DAY_MINUTE
DAY_SECOND
DEC
DECIMAL
DECLARE
DEFAULT
DELAYED
DELETE
DELETE_DOMAIN_ID
DESC
DESCRIBE
DETERMINISTIC
DISTINCT
DISTINCTROW
DIV
DO_DOMAIN_IDS
DOUBLE
DROP
DUAL
EACH
ELSE
ELSEIF
ENCLOSED
ESCAPED
EXCEPTAdded in MariaDB 10.3.0
EXISTS
EXIT
EXPLAIN
FALSE
FETCH
FLOAT
FLOAT4
FLOAT8
FOR
FORCE
FOREIGN
FROM
FULLTEXT
GENERAL
GRANT
GROUP
HAVING
HIGH_PRIORITY
HOUR_MICROSECOND
HOUR_MINUTE
HOUR_SECOND
IF
IGNORE
IGNORE_DOMAIN_IDS
IGNORE_SERVER_IDS
IN
INDEX
INFILE
INNER
INOUT
INSENSITIVE
INSERT
INT
INT1
INT2
INT3
INT4
INT8
INTEGER
INTERSECTAdded in MariaDB 10.3.0
INTERVAL
INTO
IS
ITERATE
JOIN
KEY
KEYS
KILL
LEADING
LEAVE
LEFT
LIKE
LIMIT
LINEAR
LINES
LOAD
LOCALTIME
LOCALTIMESTAMP
LOCK
LONG
LONGBLOB
LONGTEXT
LOOP
LOW_PRIORITY
MASTER_HEARTBEAT_PERIOD
MASTER_SSL_VERIFY_SERVER_CERT
MATCH
MAXVALUE
MEDIUMBLOB
MEDIUMINT
MEDIUMTEXT
MIDDLEINT
MINUTE_MICROSECOND
MINUTE_SECOND
MOD
MODIFIES
NATURAL
NOT
NO_WRITE_TO_BINLOG
NULL
NUMERIC
OFFSETAdded in MariaDB 10.6.0
ON
OPTIMIZE
OPTION
OPTIONALLY
OR
ORDER
OUT
OUTER
OUTFILE
OVERAdded in MariaDB 10.2.0
PAGE_CHECKSUM
PARSE_VCOL_EXPR
PARTITION
POSITION
PRECISION
PRIMARY
PROCEDURE
PURGE
RANGE
READ
READS
READ_WRITE
REAL
RECURSIVEAdded in MariaDB 10.2.0
REF_SYSTEM_ID
REFERENCES
REGEXP
RELEASE
RENAME
REPEAT
REPLACE
REQUIRE
RESIGNAL
RESTRICT
RETURN
RETURNING
REVOKE
RIGHT
RLIKE
ROWSAdded in MariaDB 10.2.4
SCHEMA
SCHEMAS
SECOND_MICROSECOND
SELECT
SENSITIVE
SEPARATOR
SET
SHOW
SIGNAL
SLOW
SMALLINT
SPATIAL
SPECIFIC
SQL
SQLEXCEPTION
SQLSTATE
SQLWARNING
SQL_BIG_RESULT
SQL_CALC_FOUND_ROWS
SQL_SMALL_RESULT
SSL
STARTING
STATS_AUTO_RECALC
STATS_PERSISTENT
STATS_SAMPLE_PAGES
STRAIGHT_JOIN
TABLE
TERMINATED
THEN
TINYBLOB
TINYINT
TINYTEXT
TO
TRAILING
TRIGGER
TRUE
UNDO
UNION
UNIQUE
UNLOCK
UNSIGNED
UPDATE
USAGE
USE
USING
UTC_DATE
UTC_TIME
UTC_TIMESTAMP
VALUES
VARBINARY
VARCHAR
VARCHARACTER
VARYING
WHEN
WHERE
WHILE
WINDOWAdded in MariaDB 10.2.0. From MariaDB 10.2.12 only disallowed for table aliases.
WITH
WRITE
XOR
YEAR_MONTH
ZEROFILL

Exceptions

Some keywords are exceptions for historical reasons, and are permitted as unquoted identifiers. These include:

Keyword
ACTION
BIT
DATE
ENUM
NO
TEXT
TIME
TIMESTAMP

Oracle Mode

In Oracle mode, from MariaDB 10.3, there are a number of extra reserved words:

KeywordNotes
BODY
ELSIF
GOTO
HISTORY<= MariaDB 10.3.6 only
MINUSFrom MariaDB 10.6.1
OTHERS
PACKAGE
PERIOD<= MariaDB 10.3.6 only
RAISE
ROWNUMFrom MariaDB 10.6.1
ROWTYPE
SYSDATEFrom MariaDB 10.6.1
SYSTEM<= MariaDB 10.3.6 only. Note however that SYSTEM sometimes needs to be quoted to avoid confusion with System-versioned tables.
SYSTEM_TIME<= MariaDB 10.3.6 only
VERSIONING<= MariaDB 10.3.6 only
WITHOUT<= MariaDB 10.3.6 only

Function Names

If the IGNORE_SPACE SQL_MODE flag is set, function names become reserved words.

See Also

1.1.2.12 SQLSTATE

SQLSTATE is a code which identifies SQL error conditions. It composed by five characters, which can be numbers or uppercase ASCII letters. An SQLSTATE value consists of a class (first two characters) and a subclass (last three characters).

There are three important standard classes. They all indicate in which logical group of errors the condition falls. They match to a particular keyword which can be used with DECLARE HANDLER. Also, the SQLSTATE class determines the default value for the MYSQL_ERRNO and MESSAGE_TEXT condition properties.

  • '00' means 'success'. It can not be set in any way, and can only be read via the API.
  • '01' contains all warnings, and matches to the SQLWARNING keyword. The default MYSQL_ERRNO is 1642 and default MESSAGE_TEXT is 'Unhandled user-defined warning condition'.
  • '02' is the NOT FOUND class. The default MYSQL_ERRNO is 1643 and default MESSAGE_TEXT is 'Unhandled user-defined not found condition'.
  • All other classes match the SQLEXCEPTION keyword. The default MYSQL_ERRNO is 1644 and default MESSAGE_TEXT is 'Unhandled user-defined exception condition'.

The subclass, if it is set, indicates a particular condition, or a particular group of conditions within the class. However the '000' sequence means 'no subclass'.

For example, if you try to SELECT from a table which does not exist, a 1109 error is produced, with a '42S02' SQLSTATE. '42' is the class and 'S02' is the subclass. This value matches to the SQLEXCEPTION keyword. When FETCH is called for a cursor which has already reached the end, a 1329 error is produced, with a '02000' SQLSTATE. The class is '02' and there is no subclass (because '000' means 'no subclass'). It can be handled by a NOT FOUND handlers.

The standard SQL specification says that classes beginning with 0, 1, 2, 3, 4, A, B, C, D, E, F and G are reserved for standard-defined classes, while other classes are vendor-specific. It also says that, when the class is standard-defined, subclasses starting with those characters (except for '000') are standard-defined subclasses, while other subclasses are vendor-defined. However, MariaDB and MySQL do not strictly obey this rule.

To read the SQLSTATE of a particular condition which is in the diagnostics area, the GET DIAGNOSTICS statement can be used: the property is called RETURNED_SQLSTATE. For user-defined conditions (SIGNAL and RESIGNAL statements), a SQLSTATE value must be set via the SQLSTATE clause. However, SHOW WARNINGS and SHOW ERRORS do not display the SQLSTATE.

For user-defined conditions, MariaDB and MySQL recommend the '45000' SQLSTATE class.

'HY000' is called the "general error": it is the class used for builtin conditions which do not have a specific SQLSTATE class.

A partial list of error codes and matching SQLSTATE values can be found in the page MariaDB Error Codes.

1.1.2.13 String Literals

Strings are sequences of characters and are enclosed with quotes.

The syntax is:

[_charset_name]'string' [COLLATE collation_name]

For example:

'The MariaDB Foundation'
_utf8 'Foundation' COLLATE utf8_unicode_ci;

Strings can either be enclosed in single quotes or in double quotes (the same character must be used to both open and close the string).

The ANSI SQL-standard does not permit double quotes for enclosing strings, and although MariaDB does by default, if the MariaDB server has enabled the ANSI_QUOTES_SQL SQL_MODE, double quotes will be treated as being used for identifiers instead of strings.

Strings that are next to each other are automatically concatenated. For example:

'The ' 'MariaDB ' 'Foundation'

and

'The MariaDB Foundation'

are equivalent.

The \ (backslash character) is used to escape characters (unless the SQL_MODE hasn't been set to NO_BACKSLASH_ESCAPES). For example:

'MariaDB's new features'

is not a valid string because of the single quote in the middle of the string, which is treated as if it closes the string, but is actually meant as part of the string, an apostrophe. The backslash character helps in situations like this:

'MariaDB\'s new features'

is now a valid string, and if displayed, will appear without the backslash.

SELECT 'MariaDB\'s new features';
+------------------------+
| MariaDB's new features |
+------------------------+
| MariaDB's new features |
+------------------------+

Another way to escape the quoting character is repeating it twice:

SELECT 'I''m here', """Double""";
+----------+----------+
| I'm here | "Double" |
+----------+----------+
| I'm here | "Double" |
+----------+----------+

Escape Sequences

There are other escape sequences also. Here is a full list:

Escape sequenceCharacter
\0ASCII NUL (0x00).
\'Single quote (“'”).
\"Double quote (“"”).
\bBackspace.
\nNewline, or linefeed,.
\rCarriage return.
\tTab.
\ZASCII 26 (Control+Z). See note following the table.
\\Backslash (“\”).
\%“%” character. See note following the table.
\_A “_” character. See note following the table.

Escaping the % and _ characters can be necessary when using the LIKE operator, which treats them as special characters.

The ASCII 26 character (\Z) needs to be escaped when included in a batch file which needs to be executed in Windows. The reason is that ASCII 26, in Windows, is the end of file (EOF).

Backslash (\), if not used as an escape character, must always be escaped. When followed by a character that is not in the above table, backslashes will simply be ignored.

1.1.2.14 Table Value Constructors

MariaDB starting with 10.3.3

Table Value Constructors were introduced in MariaDB 10.3.3

Syntax

VALUES ( row_value[, row_value...]), (...)...

Description

Contents

  1. Syntax
  2. Description
  3. Examples

In Unions, Views, and sub-queries, a Table Value Constructor (TVC) allows you to inject arbitrary values into the result-set. The given values must have the same number of columns as the result-set, otherwise it returns Error 1222.

Examples

Using TVC's with UNION operations:

CREATE TABLE test.t1 (val1 INT, val2 INT);
INSERT INTO test.t1 VALUES(5, 8), (3, 4), (1, 2);

SELECT * FROM test.t1
UNION
VALUES (70, 90), (100, 110);

+------+------+
| val1 | val2 |
+------+------+
|    5 |    8 | 
|    3 |    4 |
|    1 |    2 |
|   70 |   90 |
|  100 |  110 |
+------+------+

Using TVC's with a CREATE VIEW statement:

CREATE VIEW v1 AS VALUES (7, 9), (9, 10);

SELECT * FROM v1;
+---+----+
| 7 |  9 |
+---+----+
| 7 |  9 |
| 9 | 10 |
+---+----+

Using TVC with an ORDER BY clause:

SELECT * FROM test.t1
UNION
VALUES (10, 20), (30, 40), (50, 60), (70, 80)
ORDER BY val1 DESC;

Using TVC with LIMIT clause:

SELECT * FROM test.t1
UNION
VALUES (10, 20), (30, 40), (50, 60), (70, 80)
LIMIT 2 OFFSET 4;

+------+------+
| val1 | val2 |
+------+------+
|   30 |   40 | 
|   50 |   60 |
+------+------+

1.1.2.15 User-Defined Variables

Contents

  1. See Also

User-defined variables are variables which can be created by the user and exist in the session. This means that no one can access user-defined variables that have been set by another user, and when the session is closed these variables expire. However, these variables can be shared between several queries and stored programs.

User-defined variables names must be preceded by a single at character (@). While it is safe to use a reserved word as a user-variable name, the only allowed characters are ASCII letters, digits, dollar sign ($), underscore (_) and dot (.). If other characters are used, the name can be quoted in one of the following ways:

  • @`var_name`
  • @'var_name'
  • @"var_name"

These characters can be escaped as usual.

User-variables names are case insensitive, though they were case sensitive in MySQL 4.1 and older versions.

User-defined variables cannot be declared. They can be read even if no value has been set yet; in that case, they are NULL. To set a value for a user-defined variable you can use:

Since user-defined variables type cannot be declared, the only way to force their type is using CAST() or CONVERT():

SET @str = CAST(123 AS CHAR(5));

If a variable has not been used yet, its value is NULL:

SELECT @x IS NULL;
+------------+
| @x IS NULL |
+------------+
|          1 |
+------------+

It is unsafe to read a user-defined variable and set its value in the same statement (unless the command is SET), because the order of these actions is undefined.

User-defined variables can be used in most MariaDB's statements and clauses which accept an SQL expression. However there are some exceptions, like the LIMIT clause.

They must be used to PREPARE a prepared statement:

@sql = 'DELETE FROM my_table WHERE c>1;';
PREPARE stmt FROM @sql;
EXECUTE stmt;
DEALLOCATE PREPARE stmt;

Another common use is to include a counter in a query:

SET @var = 0;
SELECT a, b, c, (@var:=@var+1) AS counter FROM my_table;

See Also

1.1.3 Geographic & Geometric Features

MariaDB supports spatial extensions that enable the creation, storage and analysis of geographic features. These can be used in the Aria, MyISAM, InnoDB/XtraDB and ARCHIVE engines in MariaDB.

Partitioned tables do not support geometric types.

There are 5 related questions.

1.1.3.1 GIS Resources

Here are a few resources for those interested in GIS in MariaDB.

There are currently no differences between GIS in stable versions of MariaDB and GIS in MySQL. There are, however, some extensions and enhancements being worked on. See "MariaDB Plans - GIS" for more information.

1.1.3.2 GIS features in 5.3.3

Basic information about the existing spatial features can be found in the Geographic Features section of the Knowlegebase. The Spatial Extensions page of the MySQL manual also applies to MariaDB.

The MariaDB 5.3.3 release , contains code improving the spatial functionality in MariaDB.

MySQL operates on spatial data based on the OpenGIS standards, particularly the OpenGIS SFS (Simple feature access, SQL option).

Initial support was based on version 05-134 of the standard. MariaDB implements a subset of the 'SQL with Geometry Types' environment proposed by the OGC. And the SQL environment was extended with a set of geometry types.

MariaDB supports spatial extensions to operate on spatial features. These features are available for Aria, MyISAM, InnoDB, NDB, and ARCHIVE tables.

For spatial columns, Aria and MyISAM supports both SPATIAL and non-SPATIAL indexes. Other storage engines support non-SPATIAL indexes.

The most recent changes in the code are aimed at meeting the OpenGIS requirements. One thing missed in previous versions is that the functions which check spatial relations didn't consider the actual shape of an object, instead they operate only on their bounding rectangles. These legacy functions have been left as they are and new, properly-working functions are named with an 'ST_' prefix, in accordance with the latest OpenGIS requirements. Also, operations over geometry features were added.

The list of new functions:

Spatial operators. They produce new geometries.

NameDescription
ST_UNION(A, B)union of A and B
ST_INTERSECTION(A, B)intersection of A and B
ST_SYMDIFFERENCE(A, B)symdifference, notintersecting parts of A and B
ST_BUFFER(A, radius)returns the shape of the area that lies in 'radius' distance from the shape A.

Predicates, return boolean result of the relationship

NameDescription
ST_INTERSECTS(A, B)if A and B have an intersection
ST_CROSSES(A, B)if A and B cross
ST_EQUALS(A, B)if A and B are equal
ST_WITHIN(A, B)if A lies within B
ST_CONTAINS(A,B)if B lies within A
ST_DISJOINT(A,B)if A and B have no intersection
ST_TOUCHES(A,B)if A touches B

1.1.3.3 Geometry Types

Contents

  1. Description
  2. Examples
    1. POINT
    2. LINESTRING
    3. POLYGON
    4. MULTIPOINT
    5. MULTILINESTRING
    6. MULTIPOLYGON
    7. GEOMETRYCOLLECTION
    8. GEOMETRY

Description

MariaDB provides a standard way of creating spatial columns for geometry types, for example, with CREATE TABLE or ALTER TABLE. Currently, spatial columns are supported for MyISAM, InnoDB, NDB, and ARCHIVE tables. See also SPATIAL INDEX.

The basic geometry type is GEOMETRY. But the type can be more specific. The following types are supported:

Geometry Types
POINT
LINESTRING
POLYGON
MULTIPOINT
MULTILINESTRING
MULTIPOLYGON
GEOMETRYCOLLECTION
GEOMETRY

Examples

Note: For clarity, only one type is listed per table in the examples below, but a table row can contain multiple types. For example:

CREATE TABLE object (shapeA POLYGON, shapeB LINESTRING);

POINT

CREATE TABLE gis_point  (g POINT);
SHOW FIELDS FROM gis_point;
INSERT INTO gis_point VALUES
    (PointFromText('POINT(10 10)')),
    (PointFromText('POINT(20 10)')),
    (PointFromText('POINT(20 20)')),
    (PointFromWKB(AsWKB(PointFromText('POINT(10 20)'))));

LINESTRING

CREATE TABLE gis_line  (g LINESTRING);
SHOW FIELDS FROM gis_line;
INSERT INTO gis_line VALUES
    (LineFromText('LINESTRING(0 0,0 10,10 0)')),
    (LineStringFromText('LINESTRING(10 10,20 10,20 20,10 20,10 10)')),
    (LineStringFromWKB(AsWKB(LineString(Point(10, 10), Point(40, 10)))));

POLYGON

CREATE TABLE gis_polygon   (g POLYGON);
SHOW FIELDS FROM gis_polygon;
INSERT INTO gis_polygon VALUES
    (PolygonFromText('POLYGON((10 10,20 10,20 20,10 20,10 10))')),
    (PolyFromText('POLYGON((0 0,50 0,50 50,0 50,0 0), (10 10,20 10,20 20,10 20,10 10))')),
    (PolyFromWKB(AsWKB(Polygon(LineString(Point(0, 0), Point(30, 0), Point(30, 30), Point(0, 0))))));

MULTIPOINT

CREATE TABLE gis_multi_point (g MULTIPOINT);
SHOW FIELDS FROM gis_multi_point;
INSERT INTO gis_multi_point VALUES
    (MultiPointFromText('MULTIPOINT(0 0,10 10,10 20,20 20)')),
    (MPointFromText('MULTIPOINT(1 1,11 11,11 21,21 21)')),
    (MPointFromWKB(AsWKB(MultiPoint(Point(3, 6), Point(4, 10)))));

MULTILINESTRING

CREATE TABLE gis_multi_line (g MULTILINESTRING);
SHOW FIELDS FROM gis_multi_line;
INSERT INTO gis_multi_line VALUES
    (MultiLineStringFromText('MULTILINESTRING((10 48,10 21,10 0),(16 0,16 23,16 48))')),
    (MLineFromText('MULTILINESTRING((10 48,10 21,10 0))')),
    (MLineFromWKB(AsWKB(MultiLineString(LineString(Point(1, 2), Point(3, 5)), LineString(Point(2, 5), Point(5, 8), Point(21, 7))))));

MULTIPOLYGON

CREATE TABLE gis_multi_polygon  (g MULTIPOLYGON);
SHOW FIELDS FROM gis_multi_polygon;
INSERT INTO gis_multi_polygon VALUES
    (MultiPolygonFromText('MULTIPOLYGON(((28 26,28 0,84 0,84 42,28 26),(52 18,66 23,73 9,48 6,52 18)),((59 18,67 18,67 13,59 13,59 18)))')),
    (MPolyFromText('MULTIPOLYGON(((28 26,28 0,84 0,84 42,28 26),(52 18,66 23,73 9,48 6,52 18)),((59 18,67 18,67 13,59 13,59 18)))')),
    (MPolyFromWKB(AsWKB(MultiPolygon(Polygon(LineString(Point(0, 3), Point(3, 3), Point(3, 0), Point(0, 3)))))));

GEOMETRYCOLLECTION

CREATE TABLE gis_geometrycollection  (g GEOMETRYCOLLECTION);
SHOW FIELDS FROM gis_geometrycollection;
INSERT INTO gis_geometrycollection VALUES
    (GeomCollFromText('GEOMETRYCOLLECTION(POINT(0 0), LINESTRING(0 0,10 10))')),
    (GeometryFromWKB(AsWKB(GeometryCollection(Point(44, 6), LineString(Point(3, 6), Point(7, 9)))))),
    (GeomFromText('GeometryCollection()')),
    (GeomFromText('GeometryCollection EMPTY'));

GEOMETRY

CREATE TABLE gis_geometry (g GEOMETRY);
SHOW FIELDS FROM gis_geometry;
INSERT into gis_geometry SELECT * FROM gis_point;
INSERT into gis_geometry SELECT * FROM gis_line;
INSERT into gis_geometry SELECT * FROM gis_polygon;
INSERT into gis_geometry SELECT * FROM gis_multi_point;
INSERT into gis_geometry SELECT * FROM gis_multi_line;
INSERT into gis_geometry SELECT * FROM gis_multi_polygon;
INSERT into gis_geometry SELECT * FROM gis_geometrycollection;

1.1.3.4 Geometry Hierarchy

Description

Geometry is the base class. It is an abstract class. The instantiable subclasses of Geometry are restricted to zero-, one-, and two-dimensional geometric objects that exist in two-dimensional coordinate space. All instantiable geometry classes are defined so that valid instances of a geometry class are topologically closed (that is, all defined geometries include their boundary).

The base Geometry class has subclasses for Point, Curve, Surface, and GeometryCollection:

  • Point represents zero-dimensional objects.
  • Curve represents one-dimensional objects, and has subclass LineString, with sub-subclasses Line and LinearRing.
  • Surface is designed for two-dimensional objects and has subclass Polygon.
  • GeometryCollection has specialized zero-, one-, and two-dimensional collection classes named MultiPoint, MultiLineString, and MultiPolygon for modeling geometries corresponding to collections of Points, LineStrings, and Polygons, respectively. MultiCurve and MultiSurface are introduced as abstract superclasses that generalize the collection interfaces to handle Curves and Surfaces.

Geometry, Curve, Surface, MultiCurve, and MultiSurface are defined as non-instantiable classes. They define a common set of methods for their subclasses and are included for extensibility.

Point, LineString, Polygon, GeometryCollection, MultiPoint, MultiLineString, and MultiPolygon are instantiable classes.

1.1.3.5 Geometry Constructors

1.1.3.6 Geometry Properties

1.1.3.7 Geometry Relations

1.1.3.8 LineString Properties

1.1.3.9 MBR (Minimum Bounding Rectangle)

1.1.3.10 Point Properties

1.1.3.11 Polygon Properties

1.1.3.12 WKB

1.1.3.13 WKT

1.1.3.14 MySQL/MariaDB Spatial Support Matrix

This table shows when different spatial features were introduced into MySQL and MariaDB.

MyMySQL
MDBMariaDB
xThis feature is supported.
MBRThis feature is present, but operates on the Minimum Bounding Rectangle instead of the actual shape.
dThis feature is present, but has been deprecated and will be removed in a future version.
*This feature is present, but may not work the way you expect.
-This feature is not supported.
My 5.4.2My 5.5My 5.6.1My 5.7.4My 5.7.5My 5.7.6MDB 5.1MDB 5.3.3MDB 10.1.2MDB 10.2
InnoDB Spatial Indexes - - - - x x - - - x
MyISAM Spatial Indexes x x x x x x x x x x
Aria Spatial Indexes - - - - - - x x x x
Area x x x x x d x x x x
AsBinary x x x x x d x x x x
AsText x x x x x d x x x x
AsWKB x x x x x d x x x x
AsWKT x x x x x d x x x x
Boundary - - - - - - - - x x
Buffer - - x x x d x x x x
Centroid - x x x x d x x x x
Contains MBR MBR MBR MBR MBR d MBR MBR MBR MBR
ConvexHull - - - - x d - - x x
Crosses MBR x x x x d MBR MBR MBR MBR
Dimension x x x x x d x x x x
Disjoint MBR MBR MBR MBR MBR d MBR MBR MBR MBR
Distance MBR - - x x d - - - -
EndPoint x x x x x d x x x x
Envelope x x x x x d x x x x
Equals MBR MBR MBR MBR MBR d MBR MBR MBR MBR
My 5.4.2My 5.5My 5.6.1My 5.7.4My 5.7.5My 5.7.6MDB 5.1MDB 5.3.3MDB 10.1.2MDB 10.2
ExteriorRing x x x x x d x x x x
GeomCollFromText x x x x x d x x x x
GeomCollFromWKB x x x x x d x x x x
GeometryCollection x x x x x x x x x x
GeometryCollectionFromText x x x x x d x x x x
GeometryCollectionFromWKB x x x x x d x x x x
GeometryFromText x x x x x d x x x x
GeometryFromWKB x x x x x d x x x x
GeometryN x x x x x d x x x x
GeometryType x x x x x d x x x x
GeomFromText x x x x x d x x x x
GeomFromWKB x x x x x d x x x x
GLength x x x x x d x x x x
InteriorRingN x x x x x d x x x x
Intersects MBR MBR MBR MBR MBR d MBR MBR MBR MBR
IsClosed x x x x x d x x x x
IsEmpty - **** d x x x x
IsRing - - - - - - - - x x
IsSimple - ** x x d - x x x
LineFromText x x x x x d x x x x
My 5.4.2My 5.5My 5.6.1My 5.7.4My 5.7.5My 5.7.6MDB 5.1MDB 5.3.3MDB 10.1.2MDB 10.2
LineFromWKB x x x x x d x x x x
LineString x x x x x x x x x x
LineStringFromText x x x x x d x x x x
LineStringFromWKB x x x x x d x x x x
MBRContains MBR MBR MBR MBR MBR MBR MBR MBR MBR MBR
MBRCoveredBy - - - MBR MBR MBR - - - -
MBRDisjoint MBR MBR MBR MBR MBR MBR MBR MBR MBR MBR
MBREqual MBR MBR MBR MBR MBR MBR MBR MBR MBR MBR
MBREquals - - - MBR MBR MBR - - - MBR
MBRIntersects MBR MBR MBR MBR MBR MBR MBR MBR MBR MBR
MBROverlaps MBR MBR MBR MBR MBR MBR MBR MBR MBR MBR
MBRTouches MBR MBR MBR MBR MBR MBR MBR MBR MBR MBR
MBRWithin MBR MBR MBR MBR MBR MBR MBR MBR MBR MBR
MLineFromText x x x x x d x x x x
MLineFromWKB x x x x x d x x x x
MPointFromText x x x x x d x x x x
MPointFromWKB x x x x x d x x x x
MPolyFromText x x x x x d x x x x
MPolyFromWKB x x x x x d x x x x
MultiLineString x x x x x x x x x x
My 5.4.2My 5.5My 5.6.1My 5.7.4My 5.7.5My 5.7.6MDB 5.1MDB 5.3.3MDB 10.1.2MDB 10.2
MultiLineStringFromText x x x x x d x x x x
MultiLineStringFromWKB x x x x x d x x x x
MultiPoint x x x x x x x x x x
MultiPointFromText x x x x x d x x x x
MultiPointFromWKB x x x x x d x x x x
MultiPolygon x x x x x x x x x x
MultiPolygonFromText x x x x x d x x x x
MultiPolygonFromWKB x x x x x d x x x x
NumGeometries x x x x x d x x x x
NumInteriorRings x x x x x d x x x x
NumPoints x x x x x d x x x x
Overlaps MBR MBR MBR MBR MBR d MBR MBR MBR MBR
Point x x x x x x x x x x
PointFromText x x x x x d x x x x
PointFromWKB x x x x x d x x x x
PointOnSurface - - - - - - - - x x
PointN x x x x x d x x x x
PolyFromText x x x x x d x x x x
PolyFromWKB x x x x x d x x x x
Polygon x x x x x x x x x x
My 5.4.2My 5.5My 5.6.1My 5.7.4My 5.7.5My 5.7.6MDB 5.1MDB 5.3.3MDB 10.1.2MDB 10.2
PolygonFromText x x x x x d x x x x
PolygonFromWKB x x x x x d x x x x
SRID x x x x x d x x x x
ST_Area - - x x x x - x x x
ST_AsBinary - - x x x x - x x x
ST_AsGeoJSON - - - x x x - - - x
ST_AsText - - x x x x - x x x
ST_AsWKB - - x x x x - x x x
ST_AsWKT - - x x x x - x x x
ST_Boundary - - - - - - - - x x
ST_Buffer - - x x x x - x x x
ST_Buffer_Strategy - - - x x x - - - -
ST_Centroid - - x x x x - x x x
ST_Contains - - x x x x - x x x
ST_ConvexHull - - - - x x - - x x
ST_Crosses - - x x x x - x x x
ST_Difference - - x x x x - x x x
ST_Dimension - - x x x x - x x x
ST_Disjoint - - x x x x - x x x
ST_Distance - - x x x x - x x x
My 5.4.2My 5.5My 5.6.1My 5.7.4My 5.7.5My 5.7.6MDB 5.1MDB 5.3.3MDB 10.1.2MDB 10.2
ST_Distance_Sphere - - - - - x - - - -
ST_EndPoint - - x x x x - x x x
ST_Envelope - - x x x x - x x x
ST_Equals - - x x x x - x x x
ST_ExteriorRing - - x x x x - x x x
ST_GeoHash - - - - x x - - - -
ST_GeomCollFromText - - x x x x - x x x
ST_GeomCollFromWKB - - x x x x - x x x
ST_GeometryCollectionFromText - - x x x x - x x x
ST_GeometryCollectionFromWKB - - x x x x - x x x
ST_GeometryFromText - - x x x x - x x x
ST_GeometryFromWKB - - x x x x - x x x
ST_GeometryN - - x x x x - x x x
ST_GeometryType - - x x x x - x x x
ST_GeomFromGeoJSON - - - - x x - - - x
ST_GeomFromText - - x x x x - x x x
ST_GeomFromWKB - - x x x x - x x x
ST_InteriorRingN - - x x x x - x x x
ST_Intersection - - x x x x - x x x
ST_Intersects - - x x x x - x x x
My 5.4.2My 5.5My 5.6.1My 5.7.4My 5.7.5My 5.7.6MDB 5.1MDB 5.3.3MDB 10.1.2MDB 10.2
ST_IsClosed - - x x x x - x x x
ST_IsEmpty - - x x x x - x x x
ST_IsRing - - - - - - - - x x
ST_IsSimple - - x x x x - x x x
ST_IsValid - - - - - x - - - -
ST_LatFromGeoHash - - - - x x - - - -
ST_Length - - - - - x - x x x
ST_LineFromText - - x x x x - x x x
ST_LineFromWKB - - x x x x - x x x
ST_LineStringFromText - - x x x x - x x x
ST_LineStringFromWKB - - x x x x - x x x
ST_LongFromGeoHash - - - - x x - - - -
ST_NumGeometries - - x x x x - x x x
ST_NumInteriorRings - - x x x x - x x x
ST_NumPoints - - x x x x - x x x
ST_Overlaps - - x x x x - x x x
ST_PointFromGeoHash - - - - x x - - - -
ST_PointFromText - - x x x x - x x x
ST_PointFromWKB - - x x x x - x x x
ST_PointOnSurface - - - - - - - - x x
My 5.4.2My 5.5My 5.6.1My 5.7.4My 5.7.5My 5.7.6MDB 5.1MDB 5.3.3MDB 10.1.2MDB 10.2
ST_PointN - - x x x x - x x x
ST_PolyFromText - - x x x x - x x x
ST_PolyFromWKB - - x x x x - x x x
ST_PolygonFromText - - x x x x - x x x
ST_PolygonFromWKB - - x x x x - x x x
ST_Relate - - - - - - - - x x
ST_Simplify - - - - - x - - - -
ST_SRID - - x x x x - x x x
ST_StartPoint - - x x x x - x x x
ST_SymDifference - - x x x x - x x x
ST_Touches - - x x x x - x x x
ST_Union - - x x x x - x x x
ST_Validate - - - - - x - - - -
ST_Within - - x x x x - x x x
ST_X - - x x x x - x x x
ST_Y - - x x x x - x x x
StartPoint x x x x x d x x x x
Touches MBR x x x x d MBR MBR MBR MBR
Within MBR MBR MBR MBR MBR d MBR MBR MBR MBR
X x x x x x d x x x x
Y x x x x x d x x x x
My 5.4.2My 5.5My 5.6.1My 5.7.4My 5.7.5My 5.7.6MDB 5.1MDB 5.3.3MDB 10.1.2MDB 10.2

1.1.3.15 SPATIAL INDEX

Contents

  1. Description
    1. Data-at-Rest Encyption

Description

On MyISAM and Aria tables, as well as on InnoDB tables from MariaDB 10.2.2, MariaDB can create spatial indexes (an R-tree index) using syntax similar to that for creating regular indexes, but extended with the SPATIAL keyword. Currently, columns in spatial indexes must be declared NOT NULL.

Spatial indexes can be created when the table is created, or added after the fact like so:

  • with CREATE TABLE: 
    CREATE TABLE geom (g GEOMETRY NOT NULL, SPATIAL INDEX(g));
  • with ALTER TABLE: 
    ALTER TABLE geom ADD SPATIAL INDEX(g);
  • with CREATE INDEX: 
    CREATE SPATIAL INDEX sp_index ON geom (g);

SPATIAL INDEX creates an R-tree index. For storage engines that support non-spatial indexing of spatial columns, the engine creates a B-tree index. A B-tree index on spatial values is useful for exact-value lookups, but not for range scans.

For more information on indexing spatial columns, see CREATE INDEX.

To drop spatial indexes, use ALTER TABLE or DROP INDEX:

Data-at-Rest Encyption

Before MariaDB 10.4.3, InnoDB's spatial indexes could not be encrypted. If an InnoDB table was encrypted and if it contained spatial indexes, then those indexes would be unencrypted.

In MariaDB 10.4.3 and later, if innodb_checksum_algorithm is set to full_crc32 or strict_full_crc32, and if the table does not use ROW_FORMAT=COMPRESSED, then InnoDB spatial indexes will be encrypted if the table is encrypted.

See MDEV-12026 for more information.

1.1.3.16 GeoJSON

GeoJSON is a format for encoding various geographic data structures.

1.1.3.16.1 ST_AsGeoJSON

MariaDB starting with 10.2.4

ST_AsGeoJSON was added in MariaDB 10.2.4

Syntax

ST_AsGeoJSON(g[, max_decimals[, options]])

Description

Returns the given geometry g as a GeoJSON element. The optional max_decimals limits the maximum number of decimals displayed.

The optional options flag can be set to 1 to add a bounding box to the output.

Note that this function did not work correctly before MariaDB 10.2.8 - see MDEV-12181.

Examples

SELECT ST_AsGeoJSON(ST_GeomFromText('POINT(5.3 7.2)'));
+-------------------------------------------------+
| ST_AsGeoJSON(ST_GeomFromText('POINT(5.3 7.2)')) |
+-------------------------------------------------+
| {"type": "Point", "coordinates": [5.3, 7.2]}    |
+-------------------------------------------------+

See also

1.1.3.16.2 ST_GeomFromGeoJSON

MariaDB starting with 10.2.4

ST_GeomFromGeoJSON was added in MariaDB 10.2.4

Syntax

ST_GeomFromGeoJSON(g[, option])

Description

Given a GeoJSON input g, returns a geometry object. The option specifies what to do if g contains geometries with coordinate dimensions higher than 2.

OptionDescription
1Return an error (the default)
2 - 4The document is accepted, but the coordinates for higher coordinate dimensions are stripped off.

Note that this function did not work correctly before MariaDB 10.2.8 - see MDEV-12180.

Examples

SET @j = '{ "type": "Point", "coordinates": [5.3, 15.0]}';

SELECT ST_AsText(ST_GeomFromGeoJSON(@j));
+-----------------------------------+
| ST_AsText(ST_GeomFromGeoJSON(@j)) |
+-----------------------------------+
| POINT(5.3 15)                     |
+-----------------------------------+

1.1.4 NoSQL

MariaDB supports a lot of commands and interfaces that are closer to NoSQL than to SQL.

There are 1 related questions.

1.1.4.1 CONNECT

1.1.4.2 HANDLER

The HANDLER statements give you direct access to reading rows from the storage engine. This is much faster than normal access through SELECT as there is less parsing involved and no optimizer involved.

You can use prepared statements for HANDLER READ, which should give you a speed comparable to HandlerSocket. Also see Yoshinori Matsunobu's blog post Using MySQL as a NoSQL - A story for exceeding 750,000 qps on a commodity server.

1.1.4.2.1 HANDLER Commands

Syntax

HANDLER tbl_name OPEN [ [AS] alias]
HANDLER tbl_name READ index_name { = | >= | <= | < } (value1,value2,...)
    [ WHERE where_condition ] [LIMIT ... ]
HANDLER tbl_name READ index_name { FIRST | NEXT | PREV | LAST }
    [ WHERE where_condition ] [LIMIT ... ]
HANDLER tbl_name READ { FIRST | NEXT }
    [ WHERE where_condition ] [LIMIT ... ]
HANDLER tbl_name CLOSE

Contents

  1. Syntax
  2. Description
  3. Key Lookup
  4. Key Scans
  5. Table Scans
  6. Limitations
    1. Finding 'Old Rows'
    2. Invisible Columns
    3. System-Versioned Tables
    4. Other Limitations
  7. Error Codes
  8. See Also

Description

The HANDLER statement provides direct access to table storage engine interfaces for key lookups and key or table scans. It is available for at least Aria, Memory, MyISAM and InnoDB tables (and should work with most 'normal' storage engines, but not with system tables, MERGE or views).

HANDLER ... OPEN opens a table, allowing it to be accessible to subsequent HANDLER ... READ statements. The table can either be opened using an alias (which must then be used by HANDLER ... READ, or a table name.

The table object is only closed when HANDLER ... CLOSE is called by the session, and is not shared by other sessions.

Prepared statements work with HANDLER READ, which gives a much higher performance (50% speedup) as there is no parsing and all data is transformed in binary (without conversions to text, as with the normal protocol).

The HANDLER command does not work with partitioned tables.

Key Lookup

A key lookup is started with:

HANDLER tbl_name READ index_name { = | >= | <= | < }  (value,value) [LIMIT...]

The values stands for the value of each of the key columns. For most key types (except for HASH keys in MEMORY storage engine) you can use a prefix subset of it's columns.

If you are using LIMIT, then in case of >= or > then there is an implicit NEXT implied, while if you are using <= or < then there is an implicit PREV implied.

After the initial read, you can use

HANDLER tbl_name READ index_name NEXT [ LIMIT ... ]
or
HANDLER tbl_name READ index_name PREV [ LIMIT ... ]

to scan the rows in key order.

Note that the row order is not defined for keys with duplicated values and will vary from engine to engine.

Key Scans

You can scan a table in key order by doing:

HANDLER tbl_name READ index_name FIRST [ LIMIT ... ]
HANDLER tbl_name READ index_name NEXT  [ LIMIT ... ]

or, if the handler supports backwards key scans (most do):

HANDLER tbl_name READ index_name LAST [ LIMIT ... ]
HANDLER tbl_name READ index_name PREV [ LIMIT ... ]

Table Scans

You can scan a table in row order by doing:

HANDLER tbl_name READ FIRST [ LIMIT ... ]
HANDLER tbl_name READ NEXT  [ LIMIT ... ]

Limitations

As this is a direct interface to the storage engine, some limitations may apply for what you can do and what happens if the table changes. Here follows some of the common limitations:

Finding 'Old Rows'

HANDLER READ is not transaction safe, consistent or atomic. It's ok for the storage engine to returns rows that existed when you started the scan but that were later deleted. This can happen as the storage engine may cache rows as part of the scan from a previous read.

You may also find rows committed since the scan originally started.

Invisible Columns

HANDLER ... READ also reads the data of invisible-columns.

System-Versioned Tables

HANDLER ... READ reads everything from system-versioned tables, and so includes row_start and row_end fields, as well as all rows that have since been deleted or changed, including when history partitions are used.

Other Limitations

  • If you do an ALTER TABLE, all your HANDLER's for that table are automatically closed.
  • If you do an ALTER TABLE for a table that is used by some other connection with HANDLER, the ALTER TABLE will wait for the HANDLER to be closed.
  • For HASH keys, you must use all key parts when searching for a row.
  • For HASH keys, you can't do a key scan of all values. You can only find all rows with the same key value.
  • While each HANDLER READ command is atomic, if you do a scan in many steps, then some engines may give you error 1020 if the table changed between the commands. Please refer to the specific engine handler page if this happens.

Error Codes

  • Error 1031 (ER_ILLEGAL_HA) Table storage engine for 't1' doesn't have this option
    • If you get this for HANDLER OPEN it means the storage engine doesn't support HANDLER calls.
    • If you get this for HANDLER READ it means you are trying to use an incomplete HASH key.
  • Error 1020 (ER_CHECKREAD) Record has changed since last read in table '...'
    • This means that the table changed between two reads and the handler can't handle this case for the given scan.

See Also

1.1.4.2.2 HANDLER for MEMORY Tables

This article explains how to use HANDLER commands efficiently with MEMORY/HEAP tables.

If you want to scan a table for over different key values, not just search for exact key values, you should create your keys with 'USING BTREE':

CREATE TABLE t1 (a INT, b INT, KEY(a), KEY b USING BTREE (b)) engine=memory;

In the above table, a is a HASH key that only supports exact matches (=) while b is a BTREE key that you can use to scan the table in key order, starting from start or from a given key value.

The limitations for HANDLER READ with Memory|HEAP tables are:

Limitations for HASH keys

  • You must use all key parts when searching for a row.
  • You can't do a key scan of all values. You can only find all rows with the same key value.
  • READ NEXT gives error 1031 if the tables changed since last read.

Limitations for BTREE keys

  • READ NEXT gives error 1031 if the tables changed since last read. This limitation can be lifted in the future.

Limitations for table scans

  • READ NEXT gives error 1031 if the table was truncated since last READ call.

See also

See also the the limitations listed in HANDLER commands.

1.1.4.3 HandlerSocket

HandlerSocket gives you direct access to InnoDB and SPIDER. It is included in MariaDB as a ready-to use plugin.

HandlerSocket is a NoSQL plugin for MariaDB. It works as a daemon inside the mysqld process, accepting TCP connections, and executing requests from clients. HandlerSocket does not support SQL queries. Instead, it supports simple CRUD operations on tables.

HandlerSocket can be much faster than mysqld/libmysql in some cases because it has lower CPU, disk, and network overhead:

  1. To lower CPU usage it does not parse SQL.
  2. Next, it batch-processes requests where possible, which further reduces CPU usage and lowers disk usage.
  3. Lastly, the client/server protocol is very compact compared to mysql/libmysql, which reduces network usage.

1.1.4.3.1 HandlerSocket Installation

MariaDB starting with 5.3.0

Beginning with MariaDB 5.3.0, the HandlerSocket plugin is included in both source and binary distributions.

After MariaDB is installed, use the INSTALL PLUGIN command (as the root user) to install the HandlerSocket plugin. This command only needs to be run once, like so:

INSTALL PLUGIN handlersocket SONAME 'handlersocket.so';

In older versions, after installing the plugin, SHOW PROCESSLIST would show the HandlerSocket worker threads. With the latest versions, you first need to configure some settings. All HandlerSocket configuration options are placed in the [mysqld] section of your my.cnf file.

At least the handlersocket_address, handlersocket_port and handlersocket_port_wr options need to be set. For example:

handlersocket_address="127.0.0.1"
handlersocket_port="9998"
handlersocket_port_wr="9999"

After updating the configuration options, restart MariaDB.

On the client side, to make use of the plugin you will need to install the appropriate client library (i.e. libhsclient for C++ applications and perl-Net-HandlerSocket for perl applications, both available from the HandlerSocket website).

1.1.4.3.2 HandlerSocket Configuration Options

Contents

  1. handlersocket_accept_balance
  2. handlersocket_address
  3. handlersocket_backlog
  4. handlersocket_epoll
  5. handlersocket_plain_secret
  6. handlersocket_plain_secret_wr
  7. handlersocket_port
  8. handlersocket_port_wr
  9. handlersocket_rcvbuf
  10. handlersocket_readsize
  11. handlersocket_sndbuf
  12. handlersocket_threads
  13. handlersocket_threads_wr
  14. handlersocket_timeout
  15. handlersocket_verbose
  16. handlersocket_wrlock_timeout

The HandlerSocket plugin has the following options.

See also the Full list of MariaDB options, system and status variables.

Add the options to the [mysqld] section of your my.cnf file.

handlersocket_accept_balance

  • Description: When set to a value other than zero ('0'), handlersocket will try to balance accepted connections among threads. Default is 0 but if you use persistent connections (for example if you use client-side connection pooling) then a non-zero value is recommended.
  • Commandline: --handlersocket-accept-balance="value"
  • Scope: Global
  • Dynamic: No
  • Type: number
  • Range: 0 to 10000
  • Default Value: 0

handlersocket_address

  • Description: Specify the IP address to bind to.
  • Commandline: --handlersocket-address="value"
  • Scope: Global
  • Dynamic: No
  • Type: IP Address
  • Default Value: Empty, previously 0.0.0.0

handlersocket_backlog

  • Description: Specify the listen backlog length.
  • Commandline: --handlersocket-backlog="value"
  • Scope: Global
  • Dynamic: No
  • Type: number
  • Range: 5 to 1000000
  • Default Value: 32768

handlersocket_epoll

  • Description: Specify whether to use epoll for I/O multiplexing.
  • Commandline: --handlersocket-epoll="value"
  • Scope: Global
  • Dynamic: No
  • Type: number
  • Valid values:
    • Min: 0
    • Max: 1
  • Default Value: 1

handlersocket_plain_secret

  • Description: When set, enables plain-text authentication for the listener for read requests, with the value of the option specifying the secret authentication key.
  • Commandline: --handlersocket-plain-secret="value"
  • Dynamic: No
  • Type: string
  • Default Value: Empty

handlersocket_plain_secret_wr

  • Description: When set, enables plain-text authentication for the listener for write requests, with the value of the option specifying the secret authentication key.
  • Commandline: --handlersocket-plain-secret-wr="value"
  • Dynamic: No
  • Type: string
  • Default Value: Empty

handlersocket_port

  • Description: Specify the port to bind to for reads. An empty value disables the listener.
  • Commandline: --handlersocket-port="value"
  • Scope: Global
  • Dynamic: No
  • Type: number
  • Default Value: Empty, previously 9998

handlersocket_port_wr

  • Description: Specify the port to bind to for writes. An empty value disables the listener.
  • Commandline: --handlersocket-port-wr="value"
  • Scope: Global
  • Dynamic: No
  • Type: number
  • Default Value: Empty, previously 9999

handlersocket_rcvbuf

  • Description: Specify the maximum socket receive buffer (in bytes). If '0' then the system default is used.
  • Commandline: --handlersocket-rcvbuf="value"
  • Scope: Global
  • Dynamic: No
  • Type: number
  • Range: 0 to 1677216
  • Default Value: 0

handlersocket_readsize

  • Description: Specify the minimum length of the request buffer. Larger values consume available memory but can make handlersocket faster for large requests.
  • Commandline: --handlersocket-readsize="value"
  • Scope: Global
  • Dynamic: No
  • Type: number
  • Range: 0 to 1677216
  • Default Value: 0 (possibly 4096)

handlersocket_sndbuf

  • Description: Specify the maximum socket send buffer (in bytes). If '0' then the system default is used.
  • Commandline: --handlersocket-sndbuf="value"
  • Scope: Global
  • Dynamic: No
  • Type: number
  • Range: 0 to 1677216
  • Default Value: 0

handlersocket_threads

  • Description: Specify the number of worker threads for reads. Recommended value = ((# CPU cores) * 2).
  • Commandline: --handlersocket-threads="value"
  • Scope: Global
  • Dynamic: No
  • Type: number
  • Range: 1 to 3000
  • Default Value: 16

handlersocket_threads_wr

  • Description: Specify the number of worker threads for writes. Recommended value = 1.
  • Commandline: --handlersocket-threads-wr="value"
  • Scope: Global
  • Dynamic: No
  • Type: number
  • Range: 1 to 3000
  • Default Value: 1

handlersocket_timeout

  • Description: Specify the socket timeout in seconds.
  • Commandline: --handlersocket-timeout="value"
  • Scope: Global
  • Dynamic: No
  • Type: number
  • Range: 30 to 3600
  • Default Value: 300

handlersocket_verbose

  • Description: Specify the logging verbosity.
  • Commandline: --handlersocket-verbose="value"
  • Scope: Global
  • Dynamic: No
  • Type: number
  • Valid values:
    • Min: 0
    • Max: 10000
  • Default Value: 10

handlersocket_wrlock_timeout

  • Description: The write lock timeout in seconds. When acting on write requests, handlersocket locks an advisory lock named 'handlersocket_wr' and this option sets the timeout for it.
  • Commandline: --handlersocket-wrlock-timeout="value"
  • Scope: Global
  • Dynamic: No
  • Type: number
  • Range: 0 to 3600

1.1.4.3.3 HandlerSocket Client Libraries

In order to make use of the HandlerSocket plugin in your applications, you will need to use the appropriate client library. The following client libraries are available:

1.1.4.3.4 Testing HandlerSocket in a Source Distribution

Contents

  1. MariaDB 5.5
  2. MariaDB 5.3

MariaDB 5.5

In MariaDB 5.5, which is built using cmake, Makefile.PL is not generated automatically. If you want to run the perl tests, you will need to create it manually from Makefile.PL.in. It is fairly easy to do by replacing LIB and INC values with the correct ones. Also, libhsclient.so is not built by default; libhsclient.a can be found in plugin/handler_socket folder.

MariaDB 5.3

If you want to test or use handlersocket with a source installation of MariaDB 5.3, here is one way to do this:

  1. Compile with one of the build scripts that has the -max option, like BUILD/compile-pentium64-max or BUILD/compile-pentium64-debug-max
  2. Start mysqld with the test framework
    cd mysql-test
LD_LIBRARY_PATH=../plugin/handler_socket/libhsclient/.libs \
MTR_VERSION=1 perl mysql-test-run.pl --start-and-exit 1st \
--mysqld=--plugin-dir=../plugin/handler_socket/handlersocket/.libs \
--mysqld=--loose-handlersocket_port=9998 \
--mysqld=--loose-handlersocket_port_wr=9999 \
--master_port=9306 --mysqld=--innodb
  3. This will end with:
    Servers started, exiting
  4. Load handlersocket
    client/mysql -uroot --protocol=tcp --port=9306 \
-e 'INSTALL PLUGIN handlersocket soname "handlersocket.so"'
  5. Configure and compile the handlersocket perl module
    cd plugin/handler_socket/perl-Net-HandlerSocket
perl Makefile.PL
make
  6. If you would like to install the handlersocket perl module permanently, you should do:
    make install
    If you do this, you don't have to set PERL5LIB below.
  7. Run the handlersocket test suite
    cd plugin/handler_socket/regtest/test_01_lib
MYHOST=127.0.0.1 MYPORT=9306 LD_LIBRARY_PATH=../../libhsclient/.libs/ \
PERL5LIB=../common:../../perl-Net-HandlerSocket/lib:../../perl-Net-HandlerSocket/blib/arch/auto/Net/HandlerSocket/ ./run.sh

1.1.4.3.5 HandlerSocket External Resources

Some resources and documentation about HandlerSocket.

1.1.4.4 Dynamic Columns

Contents

  1. Dynamic Columns Basics
  2. Dynamic Columns Reference
    1. Dynamic Columns Functions
      1. COLUMN_CREATE
      2. COLUMN_ADD
      3. COLUMN_GET
      4. COLUMN_DELETE
      5. COLUMN_EXISTS
      6. COLUMN_LIST
      7. COLUMN_CHECK
      8. COLUMN_JSON
    2. Nesting Dynamic Columns
    3. Datatypes
      1. A Note About Lengths
    4. MariaDB 5.3 vs MariaDB 10.0
    5. Client-side API
    6. Limitations

Dynamic columns allow one to store different sets of columns for each row in a table. It works by storing a set of columns in a blob and having a small set of functions to manipulate it.

Dynamic columns should be used when it is not possible to use regular columns.

A typical use case is when one needs to store items that may have many different attributes (like size, color, weight, etc), and the set of possible attributes is very large and/or unknown in advance. In that case, attributes can be put into dynamic columns.

Dynamic Columns Basics

The table should have a blob column which will be used as storage for dynamic columns:

create table assets (
  item_name varchar(32) primary key, -- A common attribute for all items
  dynamic_cols  blob  -- Dynamic columns will be stored here
);

Once created, one can access dynamic columns via dynamic column functions:

Insert a row with two dynamic columns: color=blue, size=XL

INSERT INTO assets VALUES 
  ('MariaDB T-shirt', COLUMN_CREATE('color', 'blue', 'size', 'XL'));

Insert another row with dynamic columns: color=black, price=500

INSERT INTO assets VALUES
  ('Thinkpad Laptop', COLUMN_CREATE('color', 'black', 'price', 500));

Select dynamic column 'color' for all items:

SELECT item_name, COLUMN_GET(dynamic_cols, 'color' as char) AS color FROM assets;
+-----------------+-------+
| item_name       | color |
+-----------------+-------+
| MariaDB T-shirt | blue  |
| Thinkpad Laptop | black |
+-----------------+-------+

(note: the above example uses MariaDB 10.0.1. In MariaDB 5.3, columns can only be identified by numbers. See the #mariadb-53-vs-mariadb-100 section below)

It is possible to add and remove dynamic columns from a row:

-- Remove a column:
UPDATE assets SET dynamic_cols=COLUMN_DELETE(dynamic_cols, "price") 
WHERE COLUMN_GET(dynamic_cols, 'color' as char)='black'; 

-- Add a column:
UPDATE assets SET dynamic_cols=COLUMN_ADD(dynamic_cols, 'warranty', '3 years')
WHERE item_name='Thinkpad Laptop';

You can also list all columns, or (starting from MariaDB 10.0.1) get them together with their values in JSON format:

SELECT item_name, column_list(dynamic_cols) FROM assets;
+-----------------+---------------------------+
| item_name       | column_list(dynamic_cols) |
+-----------------+---------------------------+
| MariaDB T-shirt | `size`,`color`            |
| Thinkpad Laptop | `color`,`warranty`        |
+-----------------+---------------------------+

SELECT item_name, COLUMN_JSON(dynamic_cols) FROM assets;
+-----------------+----------------------------------------+
| item_name       | COLUMN_JSON(dynamic_cols)              |
+-----------------+----------------------------------------+
| MariaDB T-shirt | {"size":"XL","color":"blue"}           |
| Thinkpad Laptop | {"color":"black","warranty":"3 years"} |
+-----------------+----------------------------------------+

Dynamic Columns Reference

The rest of this page is a complete reference of dynamic columns in MariaDB

Dynamic Columns Functions

COLUMN_CREATE

COLUMN_CREATE(column_nr, value [as type], [column_nr, value [as type]]...);
COLUMN_CREATE(column_name, value [as type], [column_name, value [as type]]...);

Return a dynamic columns blob that stores the specified columns with values.

The return value is suitable for

    • storing in a table
    • further modification with other dynamic columns functions

The as type part allows one to specify the value type. In most cases, this is redundant because MariaDB will be able to deduce the type of the value. Explicit type specification may be needed when the type of the value is not apparent. For example, a literal '2012-12-01' has a CHAR type by default, one will need to specify '2012-12-01' AS DATE to have it stored as a date. See the Datatypes section for further details. Note also MDEV-597.

Typical usage:

-- MariaDB 5.3+:
INSERT INTO tbl SET dyncol_blob=COLUMN_CREATE(1 /*column id*/, "value");
-- MariaDB 10.0.1+:
INSERT INTO tbl SET dyncol_blob=COLUMN_CREATE("column_name", "value");

COLUMN_ADD

COLUMN_ADD(dyncol_blob, column_nr, value [as type], [column_nr, value [as type]]...);
COLUMN_ADD(dyncol_blob, column_name, value [as type], [column_name, value [as type]]...);

Adds or updates dynamic columns.

    • dyncol_blob must be either a valid dynamic columns blob (for example, COLUMN_CREATE returns such blob), or an empty string.
    • column_name specifies the name of the column to be added. If dyncol_blob already has a column with this name, it will be overwritten.
    • value specifies the new value for the column. Passing a NULL value will cause the column to be deleted.
    • as type is optional. See #datatypes section for a discussion about types.

The return value is a dynamic column blob after the modifications.

Typical usage:

-- MariaDB 5.3+:
UPDATE tbl SET dyncol_blob=COLUMN_ADD(dyncol_blob, 1 /*column id*/, "value") WHERE id=1;
-- MariaDB 10.0.1+:
UPDATE t1 SET dyncol_blob=COLUMN_ADD(dyncol_blob, "column_name", "value") WHERE id=1;

Note: COLUMN_ADD() is a regular function (just like CONCAT()), hence, in order to update the value in the table you have to use the UPDATE ... SET dynamic_col=COLUMN_ADD(dynamic_col, ....) pattern.

COLUMN_GET

COLUMN_GET(dyncol_blob, column_nr as type);
COLUMN_GET(dyncol_blob, column_name as type);

Get the value of a dynamic column by its name. If no column with the given name exists, NULL will be returned.

column_name as type requires that one specify the datatype of the dynamic column they are reading.

This may seem counter-intuitive: why would one need to specify which datatype they're retrieving? Can't the dynamic columns system figure the datatype from the data being stored?

The answer is: SQL is a statically-typed language. The SQL interpreter needs to know the datatypes of all expressions before the query is run (for example, when one is using prepared statements and runs "select COLUMN_GET(...)", the prepared statement API requires the server to inform the client about the datatype of the column being read before the query is executed and the server can see what datatype the column actually has).

See the Datatypes section for more information about datatypes.

COLUMN_DELETE

COLUMN_DELETE(dyncol_blob, column_nr, column_nr...);
COLUMN_DELETE(dyncol_blob, column_name, column_name...);

Delete a dynamic column with the specified name. Multiple names can be given.

The return value is a dynamic column blob after the modification.

COLUMN_EXISTS

COLUMN_EXISTS(dyncol_blob, column_nr);
COLUMN_EXISTS(dyncol_blob, column_name);

Check if a column with name column_name exists in dyncol_blob. If yes, return 1, otherwise return 0.

COLUMN_LIST

COLUMN_LIST(dyncol_blob);

Before MariaDB 10.0.1: Return a comma-separated list of column numbers. After MariaDB 10.0.1: Return a comma-separated list of column names. The names are quoted with backticks.

Example using MariaDB 10.0.1:

SELECT column_list(column_create('col1','val1','col2','val2'));
+---------------------------------------------------------+
| column_list(column_create('col1','val1','col2','val2')) |
+---------------------------------------------------------+
| `col1`,`col2`                                           |
+---------------------------------------------------------+
MariaDB starting with 10.0.1

COLUMN_CHECK

COLUMN_CHECK(dyncol_blob);

Check if dyncol_blob is a valid packed dynamic columns blob. Return value of 1 means the blob is valid, return value of 0 means it is not.

Rationale: Normally, one works with valid dynamic column blobs. Functions like COLUMN_CREATE, COLUMN_ADD, COLUMN_DELETE always return valid dynamic column blobs. However, if a dynamic column blob is accidentally truncated, or transcoded from one character set to another, it will be corrupted. This function can be used to check if a value in a blob field is a valid dynamic column blob.

Note: It is possible that a truncation cut a Dynamic Column "clearly" so that COLUMN_CHECK will not notice the corruption, but in any case of truncation a warning is issued during value storing.

This function was introduced in MariaDB 10.0.1.

COLUMN_JSON

COLUMN_JSON(dyncol_blob);

Return a JSON representation of data in dyncol_blob.

Example:

SELECT item_name, COLUMN_JSON(dynamic_cols) FROM assets;
+-----------------+----------------------------------------+
| item_name       | COLUMN_JSON(dynamic_cols)              |
+-----------------+----------------------------------------+
| MariaDB T-shirt | {"size":"XL","color":"blue"}           |
| Thinkpad Laptop | {"color":"black","warranty":"3 years"} |
+-----------------+----------------------------------------+

Limitation: COLUMN_JSON will decode nested dynamic columns at a nesting level of not more than 10 levels deep. Dynamic columns that are nested deeper than 10 levels will be shown as BINARY string, without encoding.

This function was introduced in MariaDB 10.0.1.

Nesting Dynamic Columns

It is possible to use nested dynamic columns by putting one dynamic column blob inside another. The COLUMN_JSON function will display nested columns.

SET @tmp= column_create('parent_column', column_create('child_column', 12345));
Query OK, 0 rows affected (0.00 sec)

SELECT column_json(@tmp);
+------------------------------------------+
| column_json(@tmp)                        |
+------------------------------------------+
| {"parent_column":{"child_column":12345}} |
+------------------------------------------+

SELECT column_get(column_get(@tmp, 'parent_column' AS char), 'child_column' AS int);
+------------------------------------------------------------------------------+
| column_get(column_get(@tmp, 'parent_column' as char), 'child_column' as int) |
+------------------------------------------------------------------------------+
|                                                                        12345 |
+------------------------------------------------------------------------------+

If you are trying to get a nested dynamic column as a string use 'as BINARY' as the last argument of COLUMN_GET (otherwise problems with character set conversion and illegal symbols are possible):

select column_json( column_get(
  column_create('test1', column_create('key1','value1','key2','value2','key3','value3')),
  'test1' as BINARY));

Datatypes

In SQL, one needs to define the type of each column in a table. Dynamic columns do not provide any way to declare a type in advance ("whenever there is a column 'weight', it should be integer" is not possible). However, each particular dynamic column value is stored together with its datatype.

The set of possible datatypes is mostly the same as that used by the SQL CAST and CONVERT functions. However, note that there are currently some differences - see MDEV-597.

typedynamic column internal typedescription
BINARY[(N)]DYN_COL_STRING(variable length string with binary charset)
CHAR[(N)]DYN_COL_STRING(variable length string with charset)
DATEDYN_COL_DATE(date - 3 bytes)
DATETIME[(D)]DYN_COL_DATETIME(date and time (with microseconds) - 9 bytes)
DECIMAL[(M[,D])]DYN_COL_DECIMAL(variable length binary decimal representation with MariaDB limitation)
DOUBLE[(M,D)]DYN_COL_DOUBLE(64 bit double-precision floating point)
INTEGERDYN_COL_INT(variable length, up to 64 bit signed integer)
SIGNED [INTEGER]DYN_COL_INT(variable length, up to 64 bit signed integer)
TIME[(D)]DYN_COL_TIME(time (with microseconds, may be negative) - 6 bytes)
UNSIGNED [INTEGER]DYN_COL_UINT(variable length, up to 64bit unsigned integer)

A Note About Lengths

If you're running queries like

SELECT COLUMN_GET(blob, 'colname' as CHAR) ...

without specifying a maximum length (i.e. using #as CHAR#, not as CHAR(n)), MariaDB will report the maximum length of the resultset column to be 53,6870,911 (bytes or characters?) for MariaDB 5.3-10.0.0 and 16,777,216 for MariaDB 10.0.1+. This may cause excessive memory usage in some client libraries, because they try to pre-allocate a buffer of maximum resultset width. If you suspect you're hitting this problem, use CHAR(n) whenever you're using COLUMN_GET in the select list.

MariaDB 5.3 vs MariaDB 10.0

The dynamic columns feature was introduced into MariaDB in two steps:

  1. MariaDB 5.3 was the first version to support dynamic columns. Only numbers could be used as column names in this version.
  2. In MariaDB 10.0.1, column names can be either numbers or strings. Also, the COLUMN_JSON and COLUMN_CHECK functions were added.

See also Dynamic Columns in MariaDB 10.

Client-side API

It is also possible to create or parse dynamic columns blobs on the client side. libmysql client library now includes an API for writing/reading dynamic column blobs. See dynamic-columns-api for details.

Limitations

DescriptionLimit
Max number of columns 65535
Max total length of packed dynamic columnmax_allowed_packet (1G)

1.1.4.5 Dynamic Columns from MariaDB 10

Contents

  1. Column Name Support
  2. Changes in Behavior
  3. New Functions
    1. COLUMN_CHECK
    2. COLUMN_JSON
  4. Other Changes
  5. Interface with Cassandra
  6. See Also
MariaDB starting with 10.0.1

MariaDB 10.0.1 introduced the following improvements to the dynamic columns feature.

Column Name Support

It is possible to refer to column by names. Names can be used everywhere where in MariaDB 5.3 one could use only strings:

  • Create a dynamic column blob: 
COLUMN_CREATE('int_col', 123 as int, 'double_col', 3.14 as double, 'string_col', 'text-data' as char);
  • Set a column value: 
COLUMN_ADD(dyncol_blob, 'intcol', 1234);
  • Get a column value: 
COLUMN_GET(dynstr, 'column1' as char(10));
  • Check whether a column exists 
COLUMN_EXISTS(dyncol_blob, 'column_name');

Changes in Behavior

  • Column list output now includes quoting: 
select column_list(column_create(1, 22, 2, 23));
+------------------------------------------+
| column_list(column_create(1, 22, 2, 23)) |
+------------------------------------------+
| `1`,`2`                                  |
+------------------------------------------+
select column_list(column_create('column1', 22, 'column2', 23)); 
+----------------------------------------------------------+
| column_list(column_create('column1', 22, 'column2', 23)) |
+----------------------------------------------------------+
| `column1`,`column2`                                      |
+----------------------------------------------------------+
  • Column name interpretation has been changed so that the string now is not converted to a number. So some "magic" tricks will not work any more, for example, "1test" and "1" now become different column names: 
select column_list(column_add(column_create('1a', 22), '1b', 23));
+------------------------------------------------------------+
| column_list(column_add(column_create('1a', 22), '1b', 23)) |
+------------------------------------------------------------+
| `1a`,`1b`                                                  |
+------------------------------------------------------------+
  • Old behavior: 
select column_list(column_add(column_create('1a', 22), '1b', 23));
+------------------------------------------------------------+
| column_list(column_add(column_create('1a', 22), '1b', 23)) |
+------------------------------------------------------------+
| 1                                                          |
+------------------------------------------------------------+

New Functions

The following new functions have been added to dynamic columns in MariaDB 10

COLUMN_CHECK

COLUMN_CHECK is used to check a column's integrity. When it encounters an error it does not return illegal format errors but returns false instead. It also checks integrity more thoroughly and finds errors in the dynamic column internal structures which might not be found by other functions.

select column_check(column_create('column1', 22));
+--------------------------------------------+
| column_check(column_create('column1', 22)) |
+--------------------------------------------+
|                                          1 |
+--------------------------------------------+
select column_check('abracadabra');
+-----------------------------+
| column_check('abracadabra') |
+-----------------------------+
|                           0 |
+-----------------------------+

COLUMN_JSON

COLUMN_JSON converts all dynamic column record content to a JSON object.

select column_json(column_create('column1', 1, 'column2', "two"));
+------------------------------------------------------------+
| column_json(column_create('column1', 1, 'column2', "two")) |
+------------------------------------------------------------+
| {"column1":1,"column2":"two"}                              |
+------------------------------------------------------------+

Other Changes

  • All API functions has prefix mariadb_dyncol_ (old prefix dynamic_column_ is depricated
  • API changed to be able to work with the new format (*_named functions).
  • Removed 'delete' function because deleting could be done by adding NULL value.
  • 'Time' and 'datetime' in the new format are stored without microseconds if they are 0.
  • New function added to API (except that two which are representing SQL level functions):
    • 'Unpack' the dynamic columns content to an arrays of values and names.
    • 3 functions to get any column value as string, integer (long long) or floating point (double).
  • New type of "dynamic column" row added on the API level (in SQL level output it is a string but if you use dynamic column functions to construct object it will be added as dynamic column value) which allow to add dynamic columns inside dynamic columns. JSON function represent such recursive constructions correctly but limit depth of representation as current implementation limit (internally depth of dynamic columns embedding is not limited).

Interface with Cassandra

CassandraSE is no longer actively being developed and has been removed in MariaDB 10.6. See MDEV-23024.

Some internal changes were added to dynamic columns to allow them to serve as an interface to Apache Cassandra dynamic columns. The Cassandra engine may pack all columns which were not mentioned in the MariaDB interface table definition and even bring changes in the dynamic column contents back to the cassandra columns family (the table analog in cassandra).

See Also

1.1.4.6 Dynamic Column API

This page describes the client-side API for reading and writing Dynamic Columns blobs.

Normally, you should use Dynamic column functions which are run inside the MariaDB server and allow one to access Dynamic Columns content without any client-side libraries.

If you need to read/write dynamic column blobs on the client for some reason, this API enables that.

Contents

  1. Where to get it
  2. Data structures
    1. DYNAMIC_COLUMN
    2. DYNAMIC_COLUMN_VALUE
    3. enum_dyncol_func_result
  3. Function reference
    1. mariadb_dyncol_create_many
    2. mariadb_dyncol_update_many
    3. mariadb_dyncol_exists
    4. mariadb_dyncol_column_count
    5. mariadb_dyncol_list
    6. mariadb_dyncol_get
    7. mariadb_dyncol_unpack
    8. mariadb_dyncol_has_names
    9. mariadb_dyncol_check
    10. mariadb_dyncol_json
    11. mariadb_dyncol_val_TYPE
    12. mariadb_dyncol_prepare_decimal
    13. mariadb_dyncol_value_init
    14. mariadb_dyncol_column_cmp_named

Where to get it

The API is a part of libmysql C client library. In order to use it, you need to include this header file

#include <mysql/ma_dyncol.h>

and link against libmysql.

Data structures

DYNAMIC_COLUMN

DYNAMIC_COLUMN represents a packed dynamic column blob. It is essentially a string-with-length and is defined as follows:

/* A generic-purpose arbitrary-length string defined in MySQL Client API */
typedef struct st_dynamic_string
{
  char *str;
  size_t length,max_length,alloc_increment;
} DYNAMIC_STRING;

...

typedef DYNAMIC_STRING DYNAMIC_COLUMN;

DYNAMIC_COLUMN_VALUE

Dynamic columns blob stores {name, value} pairs. DYNAMIC_COLUMN_VALUE structure is used to represent the value in accessible form.

struct st_dynamic_column_value
{
  DYNAMIC_COLUMN_TYPE type;
  union
  {
    long long long_value;
    unsigned long long ulong_value;
    double double_value;
    struct {
      MYSQL_LEX_STRING value;
      CHARSET_INFO *charset;
    } string;
    struct {
      decimal_digit_t buffer[DECIMAL_BUFF_LENGTH];
      decimal_t value;
    } decimal;
    MYSQL_TIME time_value;
  } x;
};
typedef struct st_dynamic_column_value DYNAMIC_COLUMN_VALUE;

Every value has a type, which is determined by the type member.

typestructure field
DYN_COL_NULL-
DYN_COL_INTvalue.x.long_value
DYN_COL_UINTvalue.x.ulong_value
DYN_COL_DOUBLEvalue.x.double_value
DYN_COL_STRINGvalue.x.string.value, value.x.string.charset
DYN_COL_DECIMALvalue.x.decimal.value
DYN_COL_DATETIMEvalue.x.time_value
DYN_COL_DATEvalue.x.time_value
DYN_COL_TIMEvalue.x.time_value
DYN_COL_DYNCOLvalue.x.string.value

Notes

  • Values with type DYN_COL_NULL do not ever occur in dynamic columns blobs.
  • Type DYN_COL_DYNCOL means that the value is a packed dynamic blob. This is how nested dynamic columns are done.
  • Before storing a value to value.x.decimal.value, one must call mariadb_dyncol_prepare_decimal() to initialize the space for storage.

enum_dyncol_func_result

enum enum_dyncol_func_result is used as return value.

valuenamemeaning
0ER_DYNCOL_OKOK
0ER_DYNCOL_NO(the same as ER_DYNCOL_OK but for functions which return a YES/NO)
1ER_DYNCOL_YESYES response or success
2ER_DYNCOL_TRUNCATEDOperation succeeded but the data was truncated
-1ER_DYNCOL_FORMATWrong format of the encoded string
-2ER_DYNCOL_LIMITA limit of implementation reached
-3ER_DYNCOL_RESOURCEOut of resources
-4ER_DYNCOL_DATAIncorrect input data
-5ER_DYNCOL_UNKNOWN_CHARSETUnknown character set

Result codes that are less than zero represent error conditions.

Function reference

Functions come in pairs:

  • xxx() operates on the old (pre-MariaDB-10.0.1) dynamic column blob format where columns were identified by numbers.
  • xxx_named() can operate on both old or new data format. If it modifies the blob, it will convert it to the new data format.

You should use xxx_named() functions, unless you need to keep the data compatible with MariaDB versions before 10.0.1.

mariadb_dyncol_create_many

Create a packed dynamic blob from arrays of values and names.

enum enum_dyncol_func_result
mariadb_dyncol_create_many(DYNAMIC_COLUMN *str,
                           uint column_count,
                           uint *column_numbers,
                           DYNAMIC_COLUMN_VALUE *values,
                           my_bool new_string);
enum enum_dyncol_func_result
mariadb_dyncol_create_many_named(DYNAMIC_COLUMN *str,
                                 uint column_count,
                                 MYSQL_LEX_STRING *column_keys,
                                 DYNAMIC_COLUMN_VALUE *values,
                                 my_bool new_string);

where

strOUTPacked dynamic blob will be put here
column_countINNumber of columns
column_numbersINColumn numbers array (old format)
column_keysINColumn names array (new format)
valuesINColumn values array
new_stringINIf TRUE then the str will be reinitialized (not freed) before usage

mariadb_dyncol_update_many

Add or update columns in a dynamic columns blob. To delete a column, update its value to a "non-value" of type DYN_COL_NULL

enum enum_dyncol_func_result
mariadb_dyncol_update_many(DYNAMIC_COLUMN *str,
                           uint column_count,
                           uint *column_numbers,
                           DYNAMIC_COLUMN_VALUE *values);
enum enum_dyncol_func_result
mariadb_dyncol_update_many_named(DYNAMIC_COLUMN *str,
                                 uint column_count,
                                 MYSQL_LEX_STRING *column_keys,
                                 DYNAMIC_COLUMN_VALUE *values);
strIN/OUTDynamic columns blob to be modified.
column_countINNumber of columns in following arrays
column_numbersINColumn numbers array (old format)
column_keysINColumn names array (new format)
valuesINColumn values array

mariadb_dyncol_exists

Check if column with given name exists in the blob

enum enum_dyncol_func_result
mariadb_dyncol_exists(DYNAMIC_COLUMN *str, uint column_number);
enum enum_dyncol_func_result
mariadb_dyncol_exists_named(DYNAMIC_COLUMN *str, MYSQL_LEX_STRING *column_key);
strINPacked dynamic columns string.
column_numberINColumn number (old format)
column_keyINColumn name (new format)

The function returns YES/NO or Error code

mariadb_dyncol_column_count

Get number of columns in a dynamic column blob

enum enum_dyncol_func_result
mariadb_dyncol_column_count(DYNAMIC_COLUMN *str, uint *column_count);
strINPacked dynamic columns string.
column_countOUTNumber of not NULL columns in the dynamic columns string

mariadb_dyncol_list

List columns in a dynamic column blob.

enum enum_dyncol_func_result
mariadb_dyncol_list(DYNAMIC_COLUMN *str, uint *column_count, uint **column_numbers);
enum enum_dyncol_func_result
mariadb_dyncol_list_named(DYNAMIC_COLUMN *str, uint *column_count,
                          MYSQL_LEX_STRING **column_keys);
strINPacked dynamic columns string.
column_countOUTNumber of columns in following arrays
column_numbersOUTColumn numbers array (old format). Caller should free this array.
column_keysOUTColumn names array (new format). Caller should free this array.

mariadb_dyncol_get

Get a value of one column

enum enum_dyncol_func_result
mariadb_dyncol_get(DYNAMIC_COLUMN *org, uint column_number,
                   DYNAMIC_COLUMN_VALUE *value);
enum enum_dyncol_func_result
mariadb_dyncol_get_named(DYNAMIC_COLUMN *str, MYSQL_LEX_STRING *column_key,
                         DYNAMIC_COLUMN_VALUE *value);
strINPacked dynamic columns string.
column_numberINColumn numbers array (old format)
column_keyINColumn names array (new format)
valueOUTValue of the column

If the column is not found NULL returned as a value of the column.

mariadb_dyncol_unpack

Get value of all columns 

enum enum_dyncol_func_result
mariadb_dyncol_unpack(DYNAMIC_COLUMN *str,
                      uint *column_count,
                      MYSQL_LEX_STRING **column_keys,
                      DYNAMIC_COLUMN_VALUE **values);
strINPacked dynamic columns string to unpack.
column_countOUTNumber of columns in following arrays
column_keysOUTColumn names array (should be free by caller)
valuesOUTValues of the columns array (should be free by caller)

mariadb_dyncol_has_names

Check whether the dynamic columns blob uses new data format (the one where columns are identified by names)

my_bool mariadb_dyncol_has_names(DYNAMIC_COLUMN *str);
strINPacked dynamic columns string.

mariadb_dyncol_check

Check whether dynamic column blob has correct data format.

enum enum_dyncol_func_result
mariadb_dyncol_check(DYNAMIC_COLUMN *str);
strINPacked dynamic columns string.

mariadb_dyncol_json

Get contents od a dynamic columns blob in a JSON form

enum enum_dyncol_func_result
mariadb_dyncol_json(DYNAMIC_COLUMN *str, DYNAMIC_STRING *json);
strINPacked dynamic columns string.
jsonOUTJSON representation

mariadb_dyncol_val_TYPE

Get dynamic column value as one of the base types

enum enum_dyncol_func_result
mariadb_dyncol_val_str(DYNAMIC_STRING *str, DYNAMIC_COLUMN_VALUE *val,
                       CHARSET_INFO *cs, my_bool quote);
enum enum_dyncol_func_result
mariadb_dyncol_val_long(longlong *ll, DYNAMIC_COLUMN_VALUE *val);
enum enum_dyncol_func_result
mariadb_dyncol_val_double(double *dbl, DYNAMIC_COLUMN_VALUE *val);
str or ll or dblOUTvalue of the column
valINValue

mariadb_dyncol_prepare_decimal

Initialize DYNAMIC_COLUMN_VALUE before value of value.x.decimal.value can be set

void mariadb_dyncol_prepare_decimal(DYNAMIC_COLUMN_VALUE *value);
valueOUTValue of the column

This function links value.x.decimal.value to value.x.decimal.buffer.

mariadb_dyncol_value_init

Initialize a DYNAMIC_COLUMN_VALUE structure to a safe default.

#define mariadb_dyncol_value_init(V) (V)->type= DYN_COL_NULL

mariadb_dyncol_column_cmp_named

Compare two column names (currently, column names are compared with memcmp())

int mariadb_dyncol_column_cmp_named(const MYSQL_LEX_STRING *s1,
                                    const MYSQL_LEX_STRING *s2);

1.1.4.7 JSON Functions

1.1.4.8 LOAD_FILE

1.1.5 Operators

Operators can be used for comparing values or for assigning values. There are several operators and they may be used in different SQL statements and clauses. Some can be used somewhat on their own, not within an SQL statement clause.

For comparing values—string or numeric—you can use symbols such as the equal-sign (i.e., =) or the exclamation point and the equal-sign together (i.e., !=). You might use these in WHERE clauses or within a flow-control statement or function (e.g., IF( )). You can also use basic regular expressions with the LIKE operator.

For assigning values, you can also use the equal-sign or other arithmetic symbols (e.g. plus-sign). You might do this with the SET statement or in a SET clause in an UPDATE statement.

Arithmetic Operators

Assignment Operators

Bit Functions and Operators

Comparison Operators

Logical Operators

Other Operators Articles

There are 3 related questions.

1.1.5.1 Arithmetic Operators

Arithmetic operators for addition, subtraction, multiplication, division and the modulo operator

1.1.5.1.1 Addition Operator (+)

1.1.5.1.2 DIV

1.1.5.1.3 Division Operator (/)

1.1.5.1.4 MOD

1.1.5.1.5 Modulo Operator (%)

1.1.5.1.6 Multiplication Operator (*)

1.1.5.1.7 Subtraction Operator (-)

1.1.5.2 Assignment Operators

Operators for assigning a value

1.1.5.2.1 Assignment Operator (:=)

Syntax

var_name := expr

Description

Assignment operator for assigning a value. The value on the right is assigned to the variable on left.

Unlike the = operator, := can always be used to assign a value to a variable.

This operator works with both user-defined variables and local variables.

When assigning the same value to several variables, LAST_VALUE() can be useful.

Examples

 SELECT @x := 10;
+----------+
| @x := 10 |
+----------+
|       10 |
+----------+

SELECT @x, @y := @x;
+------+----------+
| @x   | @y := @x |
+------+----------+
|   10 |       10 |
+------+----------+

1.1.5.2.2 Assignment Operator (=)

Syntax

identifier = expr

Contents

  1. Syntax
  2. Description
  3. Examples

Description

The equal sign is used as both an assignment operator in certain contexts, and as a comparison operator. When used as assignment operator, the value on the right is assigned to the variable (or column, in some contexts) on the left.

Since its use can be ambiguous, unlike the := assignment operator, the = assignment operator cannot be used in all contexts, and is only valid as part of a SET statement, or the SET clause of an UPDATE statement

This operator works with both user-defined variables and local variables.

Examples

UPDATE table_name SET x = 2 WHERE x > 100;

SET @x = 1, @y := 2;

1.1.5.3 Bit Functions and Operators

1.1.5.4 Comparison Operators

The comparison operators include: !=, <, <=, <=>, >=, >, etc...

1.1.5.4.1 Not Equal Operator: !=

Syntax

<>, !=

Contents

  1. Syntax
  2. Description
  3. Examples

Description

Not equal operator. Evaluates both SQL expressions and returns 1 if they are not equal and 0 if they are equal, or NULL if either expression is NULL. If the expressions return different data types, (for instance, a number and a string), performs type conversion.

When used in row comparisons these two queries return the same results:

SELECT (t1.a, t1.b) != (t2.x, t2.y) 
FROM t1 INNER JOIN t2;

SELECT (t1.a != t2.x) OR (t1.b != t2.y)
FROM t1 INNER JOIN t2;

Examples

SELECT '.01' <> '0.01';
+-----------------+
| '.01' <> '0.01' |
+-----------------+
|               1 |
+-----------------+

SELECT .01 <> '0.01';
+---------------+
| .01 <> '0.01' |
+---------------+
|             0 |
+---------------+

SELECT 'zapp' <> 'zappp';
+-------------------+
| 'zapp' <> 'zappp' |
+-------------------+
|                 1 |
+-------------------+

1.1.5.4.2 <

Syntax

<

Contents

  1. Syntax
  2. Description
  3. Examples

Description

Less than operator. Evaluates both SQL expressions and returns 1 if the left value is less than the right value and 0 if it is not, or NULL if either expression is NULL. If the expressions return different data types, (for instance, a number and a string), performs type conversion.

When used in row comparisons these two queries return the same results:

SELECT (t1.a, t1.b) < (t2.x, t2.y) 
FROM t1 INNER JOIN t2;

SELECT (t1.a < t2.x) OR ((t1.a = t2.x) AND (t1.b < t2.y))
FROM t1 INNER JOIN t2;

Examples

SELECT 2 < 2;
+-------+
| 2 < 2 |
+-------+
|     0 |
+-------+

Type conversion:

SELECT 3<'4';
+-------+
| 3<'4' |
+-------+
|     1 |
+-------+

Case insensitivity - see Character Sets and Collations:

SELECT 'a'<'A';
+---------+
| 'a'<'A' |
+---------+
|       0 |
+---------+

1.1.5.4.3 <=

Syntax

<=

Contents

  1. Syntax
  2. Description
  3. Examples

Description

Less than or equal operator. Evaluates both SQL expressions and returns 1 if the left value is less than or equal to the right value and 0 if it is not, or NULL if either expression is NULL. If the expressions return different data types, (for instance, a number and a string), performs type conversion.

When used in row comparisons these two queries return the same results:

SELECT (t1.a, t1.b) <= (t2.x, t2.y) 
FROM t1 INNER JOIN t2;

SELECT (t1.a < t2.x) OR ((t1.a = t2.x) AND (t1.b <= t2.y))
FROM t1 INNER JOIN t2;

Examples

SELECT 0.1 <= 2;
+----------+
| 0.1 <= 2 |
+----------+
|        1 |
+----------+

SELECT 'a'<='A';
+----------+
| 'a'<='A' |
+----------+
|        1 |
+----------+

1.1.5.4.4 <=>

Syntax

<=>

Description

NULL-safe equal operator. It performs an equality comparison like the = operator, but returns 1 rather than NULL if both operands are NULL, and 0 rather than NULL if one operand is NULL.

a <=> b is equivalent to a = b OR (a IS NULL AND b IS NULL).

When used in row comparisons these two queries return the same results:

SELECT (t1.a, t1.b) <=> (t2.x, t2.y) 
FROM t1 INNER JOIN t2;

SELECT (t1.a <=> t2.x) AND (t1.b <=> t2.y)
FROM t1 INNER JOIN t2;

See also NULL Values in MariaDB.

Examples

SELECT 1 <=> 1, NULL <=> NULL, 1 <=> NULL;
+---------+---------------+------------+
| 1 <=> 1 | NULL <=> NULL | 1 <=> NULL |
+---------+---------------+------------+
|       1 |             1 |          0 |
+---------+---------------+------------+

SELECT 1 = 1, NULL = NULL, 1 = NULL;
+-------+-------------+----------+
| 1 = 1 | NULL = NULL | 1 = NULL |
+-------+-------------+----------+
|     1 |        NULL |     NULL |
+-------+-------------+----------+

1.1.5.4.5 =

Syntax

left_expr = right_expr

Contents

  1. Syntax
  2. Description
  3. Examples

Description

Equal operator. Evaluates both SQL expressions and returns 1 if they are equal, 0 if they are not equal, or NULL if either expression is NULL. If the expressions return different data types (for example, a number and a string), a type conversion is performed.

When used in row comparisons these two queries are synonymous and return the same results:

SELECT (t1.a, t1.b) = (t2.x, t2.y) FROM t1 INNER JOIN t2;

SELECT (t1.a = t2.x) AND (t1.b = t2.y) FROM t1 INNER JOIN t2;

To perform a NULL-safe comparison, use the <=> operator.

= can also be used as an assignment operator.

Examples

SELECT 1 = 0;
+-------+
| 1 = 0 |
+-------+
|     0 |
+-------+

SELECT '0' = 0;
+---------+
| '0' = 0 |
+---------+
|       1 |
+---------+

SELECT '0.0' = 0;
+-----------+
| '0.0' = 0 |
+-----------+
|         1 |
+-----------+

SELECT '0.01' = 0;
+------------+
| '0.01' = 0 |
+------------+
|          0 |
+------------+

SELECT '.01' = 0.01;
+--------------+
| '.01' = 0.01 |
+--------------+
|            1 |
+--------------+

SELECT (5 * 2) = CONCAT('1', '0');
+----------------------------+
| (5 * 2) = CONCAT('1', '0') |
+----------------------------+
|                          1 |
+----------------------------+

SELECT 1 = NULL;
+----------+
| 1 = NULL |
+----------+
|     NULL |
+----------+

SELECT NULL = NULL;
+-------------+
| NULL = NULL |
+-------------+
|        NULL |
+-------------+

1.1.5.4.6 >

Syntax

>

Contents

  1. Syntax
  2. Description
  3. Examples

Description

Greater than operator. Evaluates both SQL expressions and returns 1 if the left value is greater than the right value and 0 if it is not, or NULL if either expression is NULL. If the expressions return different data types, (for instance, a number and a string), performs type conversion.

When used in row comparisons these two queries return the same results:

SELECT (t1.a, t1.b) > (t2.x, t2.y) 
FROM t1 INNER JOIN t2;

SELECT (t1.a > t2.x) OR ((t1.a = t2.x) AND (t1.b > t2.y))
FROM t1 INNER JOIN t2;

Examples

SELECT 2 > 2;
+-------+
| 2 > 2 |
+-------+
|     0 |
+-------+

SELECT 'b' > 'a';
+-----------+
| 'b' > 'a' |
+-----------+
|         1 |
+-----------+

1.1.5.4.7 >=

Syntax

>=

Contents

  1. Syntax
  2. Description
  3. Examples

Description

Greater than or equal operator. Evaluates both SQL expressions and returns 1 if the left value is greater than or equal to the right value and 0 if it is not, or NULL if either expression is NULL. If the expressions return different data types, (for instance, a number and a string), performs type conversion.

When used in row comparisons these two queries return the same results:

SELECT (t1.a, t1.b) >= (t2.x, t2.y) 
FROM t1 INNER JOIN t2;

SELECT (t1.a > t2.x) OR ((t1.a = t2.x) AND (t1.b >= t2.y))
FROM t1 INNER JOIN t2;

Examples

SELECT 2 >= 2;
+--------+
| 2 >= 2 |
+--------+
|      1 |
+--------+

SELECT 'A' >= 'a';
+------------+
| 'A' >= 'a' |
+------------+
|          1 |
+------------+

1.1.5.4.8 BETWEEN AND

Syntax

expr BETWEEN min AND max

Contents

  1. Syntax
  2. Description
  3. Examples

Description

If expr is greater than or equal to min and expr is less than or equal to max, BETWEEN returns 1, otherwise it returns 0. This is equivalent to the expression (min <= expr AND expr <= max) if all the arguments are of the same type. Otherwise type conversion takes place according to the rules described at Type Conversion, but applied to all the three arguments.

Examples

SELECT 1 BETWEEN 2 AND 3;
+-------------------+
| 1 BETWEEN 2 AND 3 |
+-------------------+
|                 0 |
+-------------------+

SELECT 'b' BETWEEN 'a' AND 'c';
+-------------------------+
| 'b' BETWEEN 'a' AND 'c' |
+-------------------------+
|                       1 |
+-------------------------+

SELECT 2 BETWEEN 2 AND '3';
+---------------------+
| 2 BETWEEN 2 AND '3' |
+---------------------+
|                   1 |
+---------------------+

SELECT 2 BETWEEN 2 AND 'x-3';
+-----------------------+
| 2 BETWEEN 2 AND 'x-3' |
+-----------------------+
|                     0 |
+-----------------------+
1 row in set, 1 warning (0.00 sec)

Warning (Code 1292): Truncated incorrect DOUBLE value: 'x-3'

NULL:

SELECT 1 BETWEEN 1 AND NULL;
+----------------------+
| 1 BETWEEN 1 AND NULL |
+----------------------+
|                 NULL |
+----------------------+

DATE, DATETIME and TIMESTAMP examples. Omitting the time component compares against 00:00, so later times on the same date are not returned:

CREATE TABLE `x` (
  a date ,
  b datetime,
  c timestamp
)

INSERT INTO x VALUES 
 ('2018-11-11', '2018-11-11 05:15', '2018-11-11 05:15'), 
 ('2018-11-12', '2018-11-12 05:15', '2018-11-12 05:15'); 

SELECT * FROM x WHERE a BETWEEN '2018-11-11' AND '2018-11-12';
+------------+---------------------+---------------------+
| a          | b                   | c                   |
+------------+---------------------+---------------------+
| 2018-11-11 | 2018-11-11 05:15:00 | 2018-11-11 05:15:00 |
| 2018-11-12 | 2018-11-12 05:15:00 | 2018-11-12 05:15:00 |
+------------+---------------------+---------------------+

SELECT * FROM x WHERE b BETWEEN '2018-11-11' AND '2018-11-12';
+------------+---------------------+---------------------+
| a          | b                   | c                   |
+------------+---------------------+---------------------+
| 2018-11-11 | 2018-11-11 05:15:00 | 2018-11-11 05:15:00 |
+------------+---------------------+---------------------+

SELECT * FROM x WHERE c BETWEEN '2018-11-11' AND '2018-11-12';
+------------+---------------------+---------------------+
| a          | b                   | c                   |
+------------+---------------------+---------------------+
| 2018-11-11 | 2018-11-11 05:15:00 | 2018-11-11 05:15:00 |
+------------+---------------------+---------------------+

1.1.5.4.9 COALESCE

Syntax

COALESCE(value,...)

Description

Returns the first non-NULL value in the list, or NULL if there are no non-NULL values. At least one parameter must be passed.

The function is useful when substituting a default value for null values when displaying data.

See also NULL Values in MariaDB.

Examples

SELECT COALESCE(NULL,1);
+------------------+
| COALESCE(NULL,1) |
+------------------+
|                1 |
+------------------+

SELECT COALESCE(NULL,NULL,NULL);
+--------------------------+
| COALESCE(NULL,NULL,NULL) |
+--------------------------+
|                     NULL |
+--------------------------+

When two arguments are given, COALESCE() is the same as IFNULL():

SET @a=NULL, @b=1;

SELECT COALESCE(@a, @b), IFNULL(@a, @b);
+------------------+----------------+
| COALESCE(@a, @b) | IFNULL(@a, @b) |
+------------------+----------------+
|                1 |              1 |
+------------------+----------------+

Hex type confusion:

CREATE TABLE t1 (a INT, b VARCHAR(10));
INSERT INTO t1 VALUES (0x31, 0x61),(COALESCE(0x31), COALESCE(0x61));

SELECT * FROM t1;
+------+------+
| a    | b    |
+------+------+
|   49 | a    |
|    1 | a    |
+------+------+

The reason for the differing results above is that when 0x31 is inserted directly to the column, it's treated as a number (see Hexadecimal Literals), while when 0x31 is passed to COALESCE(), it's treated as a string, because:

  • HEX values have a string data type by default.
  • COALESCE() has the same data type as the argument.

Substituting zero for NULL (in this case when the aggregate function returns NULL after finding no rows):

SELECT SUM(score) FROM student;
+------------+
| SUM(score) |
+------------+
|       NULL |
+------------+

SELECT COALESCE(SUM(score),0) FROM student;
+------------------------+
| COALESCE(SUM(score),0) |
+------------------------+
|                      0 |
+------------------------+

See also

1.1.5.4.10 GREATEST

Syntax

GREATEST(value1,value2,...)

Description

With two or more arguments, returns the largest (maximum-valued) argument. The arguments are compared using the same rules as for LEAST().

Examples

SELECT GREATEST(2,0);
+---------------+
| GREATEST(2,0) |
+---------------+
|             2 |
+---------------+

SELECT GREATEST(34.0,3.0,5.0,767.0);
+------------------------------+
| GREATEST(34.0,3.0,5.0,767.0) |
+------------------------------+
|                        767.0 |
+------------------------------+

SELECT GREATEST('B','A','C');
+-----------------------+
| GREATEST('B','A','C') |
+-----------------------+
| C                     |
+-----------------------+

1.1.5.4.11 IN

Syntax

expr IN (value,...)

Description

Returns 1 if expr is equal to any of the values in the IN list, else returns 0. If all values are constants, they are evaluated according to the type of expr and sorted. The search for the item then is done using a binary search. This means IN is very quick if the IN value list consists entirely of constants. Otherwise, type conversion takes place according to the rules described at Type Conversion, but applied to all the arguments.

If expr is NULL, IN always returns NULL. If at least one of the values in the list is NULL, and one of the comparisons is true, the result is 1. If at least one of the values in the list is NULL and none of the comparisons is true, the result is NULL.

Examples

SELECT 2 IN (0,3,5,7);
+----------------+
| 2 IN (0,3,5,7) |
+----------------+
|              0 |
+----------------+

SELECT 'wefwf' IN ('wee','wefwf','weg');
+----------------------------------+
| 'wefwf' IN ('wee','wefwf','weg') |
+----------------------------------+
|                                1 |
+----------------------------------+

Type conversion:

SELECT 1 IN ('1', '2', '3');
+----------------------+
| 1 IN ('1', '2', '3') |
+----------------------+
|                    1 |
+----------------------+

SELECT NULL IN (1, 2, 3);
+-------------------+
| NULL IN (1, 2, 3) |
+-------------------+
|              NULL |
+-------------------+

SELECT 1 IN (1, 2, NULL);
+-------------------+
| 1 IN (1, 2, NULL) |
+-------------------+
|                 1 |
+-------------------+

SELECT 5 IN (1, 2, NULL);
+-------------------+
| 5 IN (1, 2, NULL) |
+-------------------+
|              NULL |
+-------------------+

See Also

1.1.5.4.12 INTERVAL

Syntax

INTERVAL(N,N1,N2,N3,...)

Description

Returns the index of the last argument that is less than the first argument or is NULL.

Returns 0 if N < N1, 1 if N < N2, 2 if N < N3 and so on or -1 if N is NULL. All arguments are treated as integers. It is required that N1 < N2 < N3 < ... < Nn for this function to work correctly. This is because a fast binary search is used.

Examples

SELECT INTERVAL(23, 1, 15, 17, 30, 44, 200);
+--------------------------------------+
| INTERVAL(23, 1, 15, 17, 30, 44, 200) |
+--------------------------------------+
|                                    3 |
+--------------------------------------+

SELECT INTERVAL(10, 1, 10, 100, 1000);
+--------------------------------+
| INTERVAL(10, 1, 10, 100, 1000) |
+--------------------------------+
|                              2 |
+--------------------------------+

SELECT INTERVAL(22, 23, 30, 44, 200);
+-------------------------------+
| INTERVAL(22, 23, 30, 44, 200) |
+-------------------------------+
|                             0 |
+-------------------------------+

SELECT INTERVAL(10, 2, NULL);
+-----------------------+
| INTERVAL(10, 2, NULL) |
+-----------------------+
|                     2 |
+-----------------------+

1.1.5.4.13 IS

Syntax

IS boolean_value

Description

Tests a value against a boolean value, where boolean_value can be TRUE, FALSE, or UNKNOWN.

There is an important difference between using IS TRUE or comparing a value with TRUE using =. When using =, only 1 equals to TRUE. But when using IS TRUE, all values which are logically true (like a number > 1) return TRUE.

Examples

SELECT 1 IS TRUE, 0 IS FALSE, NULL IS UNKNOWN;
+-----------+------------+-----------------+
| 1 IS TRUE | 0 IS FALSE | NULL IS UNKNOWN |
+-----------+------------+-----------------+
|         1 |          1 |               1 |
+-----------+------------+-----------------+

Difference between = and IS TRUE:

SELECT 2 = TRUE, 2 IS TRUE;
+----------+-----------+
| 2 = TRUE | 2 IS TRUE |
+----------+-----------+
|        0 |         1 |
+----------+-----------+

See Also

1.1.5.4.14 IS NOT

Syntax

IS NOT boolean_value

Description

Tests a value against a boolean value, where boolean_value can be TRUE, FALSE, or UNKNOWN.

Examples

SELECT 1 IS NOT UNKNOWN, 0 IS NOT UNKNOWN, NULL IS NOT UNKNOWN;
+------------------+------------------+---------------------+
| 1 IS NOT UNKNOWN | 0 IS NOT UNKNOWN | NULL IS NOT UNKNOWN |
+------------------+------------------+---------------------+
|                1 |                1 |                   0 |
+------------------+------------------+---------------------+

SELECT NULL IS NOT TRUE, NULL IS NOT FALSE;
+------------------+-------------------+
| NULL IS NOT TRUE | NULL IS NOT FALSE |
+------------------+-------------------+
|                1 |                 1 |
+------------------+-------------------+

1.1.5.4.15 IS NOT NULL

Syntax

IS NOT NULL

Description

Tests whether a value is not NULL. See also NULL Values in MariaDB.

Examples

SELECT 1 IS NOT NULL, 0 IS NOT NULL, NULL IS NOT NULL;
+---------------+---------------+------------------+
| 1 IS NOT NULL | 0 IS NOT NULL | NULL IS NOT NULL |
+---------------+---------------+------------------+
|             1 |             1 |                0 |
+---------------+---------------+------------------+

See also

1.1.5.4.16 IS NULL

Syntax

IS NULL

Description

Tests whether a value is NULL. See also NULL Values in MariaDB.

Examples

SELECT 1 IS NULL, 0 IS NULL, NULL IS NULL;
+-----------+-----------+--------------+
| 1 IS NULL | 0 IS NULL | NULL IS NULL |
+-----------+-----------+--------------+
|         0 |         0 |            1 |
+-----------+-----------+--------------+

Compatibility

Some ODBC applications use the syntax auto_increment_field IS NOT NULL to find the latest row that was inserted with an autogenerated key value. If your applications need this, you can set the sql_auto_is_null variable to 1.

SET @@sql_auto_is_null=1;
CREATE TABLE t1 (auto_increment_column INT NOT NULL AUTO_INCREMENT PRIMARY KEY);
INSERT INTO t1 VALUES (NULL);
SELECT * FROM t1 WHERE auto_increment_column IS NULL;

+-----------------------+
| auto_increment_column |
+-----------------------+
|                     1 |
+-----------------------+

See also

1.1.5.4.17 ISNULL

Syntax

ISNULL(expr)

Description

If expr is NULL, ISNULL() returns 1, otherwise it returns 0.

See also NULL Values in MariaDB.

Examples

SELECT ISNULL(1+1);
+-------------+
| ISNULL(1+1) |
+-------------+
|           0 |
+-------------+

SELECT ISNULL(1/0);
+-------------+
| ISNULL(1/0) |
+-------------+
|           1 |
+-------------+

1.1.5.4.18 LEAST

Syntax

LEAST(value1,value2,...)

Description

With two or more arguments, returns the smallest (minimum-valued) argument. The arguments are compared using the following rules:

  • If the return value is used in an INTEGER context or all arguments are integer-valued, they are compared as integers.
  • If the return value is used in a REAL context or all arguments are real-valued, they are compared as reals.
  • If any argument is a case-sensitive string, the arguments are compared as case-sensitive strings.
  • In all other cases, the arguments are compared as case-insensitive strings.

LEAST() returns NULL if any argument is NULL.

Examples

SELECT LEAST(2,0);
+------------+
| LEAST(2,0) |
+------------+
|          0 |
+------------+

SELECT LEAST(34.0,3.0,5.0,767.0);
+---------------------------+
| LEAST(34.0,3.0,5.0,767.0) |
+---------------------------+
|                       3.0 |
+---------------------------+

SELECT LEAST('B','A','C');
+--------------------+
| LEAST('B','A','C') |
+--------------------+
| A                  |
+--------------------+

1.1.5.4.19 NOT BETWEEN

Syntax

expr NOT BETWEEN min AND max

Description

This is the same as NOT (expr BETWEEN min AND max).

Note that the meaning of the alternative form NOT expr BETWEEN min AND max is affected by the HIGH_NOT_PRECEDENCE SQL_MODE flag.

Examples

SELECT 1 NOT BETWEEN 2 AND 3;
+-----------------------+
| 1 NOT BETWEEN 2 AND 3 |
+-----------------------+
|                     1 |
+-----------------------+

SELECT 'b' NOT BETWEEN 'a' AND 'c';
+-----------------------------+
| 'b' NOT BETWEEN 'a' AND 'c' |
+-----------------------------+
|                           0 |
+-----------------------------+

NULL:

SELECT 1 NOT BETWEEN 1 AND NULL;
+--------------------------+
| 1 NOT BETWEEN 1 AND NULL |
+--------------------------+
|                     NULL |
+--------------------------+

1.1.5.4.20 NOT IN

Syntax

expr NOT IN (value,...)

Description

This is the same as NOT (expr IN (value,...)).

Examples

SELECT 2 NOT IN (0,3,5,7);
+--------------------+
| 2 NOT IN (0,3,5,7) |
+--------------------+
|                  1 |
+--------------------+

SELECT 'wefwf' NOT IN ('wee','wefwf','weg');
+--------------------------------------+
| 'wefwf' NOT IN ('wee','wefwf','weg') |
+--------------------------------------+
|                                    0 |
+--------------------------------------+

SELECT 1 NOT IN ('1', '2', '3');
+--------------------------+
| 1 NOT IN ('1', '2', '3') |
+--------------------------+
|                        0 |
+--------------------------+

NULL:

SELECT NULL NOT IN (1, 2, 3);
+-----------------------+
| NULL NOT IN (1, 2, 3) |
+-----------------------+
|                  NULL |
+-----------------------+

SELECT 1 NOT IN (1, 2, NULL);
+-----------------------+
| 1 NOT IN (1, 2, NULL) |
+-----------------------+
|                     0 |
+-----------------------+

SELECT 5 NOT IN (1, 2, NULL);
+-----------------------+
| 5 NOT IN (1, 2, NULL) |
+-----------------------+
|                  NULL |
+-----------------------+

1.1.5.5 Logical Operators

NOT, AND, Exclusive OR and OR

1.1.5.5.1 !

Syntax

NOT, !

Contents

  1. Syntax
  2. Description
  3. Examples

Description

Logical NOT. Evaluates to 1 if the operand is 0, to 0 if the operand is non-zero, and NOT NULL returns NULL.

By default, the ! operator has a higher precedence. If the HIGH_NOT_PRECEDENCE SQL_MODE flag is set, NOT and ! have the same precedence.

Examples

SELECT NOT 10;
+--------+
| NOT 10 |
+--------+
|      0 |
+--------+

SELECT NOT 0;
+-------+
| NOT 0 |
+-------+
|     1 |
+-------+

SELECT NOT NULL;
+----------+
| NOT NULL |
+----------+
|     NULL |
+----------+

SELECT ! (1+1);
+---------+
| ! (1+1) |
+---------+
|       0 |
+---------+

SELECT ! 1+1;
+-------+
| ! 1+1 |
+-------+
|     1 |
+-------+

1.1.5.5.2 &&

Syntax

AND, &&

Contents

  1. Syntax
  2. Description
  3. Examples

Description

Logical AND. Evaluates to 1 if all operands are non-zero and not NULL, to 0 if one or more operands are 0, otherwise NULL is returned.

For this operator, short-circuit evaluation can be used.

Examples

SELECT 1 && 1;
+--------+
| 1 && 1 |
+--------+
|      1 |
+--------+

SELECT 1 && 0;
+--------+
| 1 && 0 |
+--------+
|      0 |
+--------+

SELECT 1 && NULL;
+-----------+
| 1 && NULL |
+-----------+
|      NULL |
+-----------+

SELECT 0 && NULL;
+-----------+
| 0 && NULL |
+-----------+
|         0 |
+-----------+

SELECT NULL && 0;
+-----------+
| NULL && 0 |
+-----------+
|         0 |
+-----------+

1.1.5.5.3 XOR

Syntax

XOR

Contents

  1. Syntax
  2. Description
  3. Examples

Description

XOR stands for eXclusive OR. Returns NULL if either operand is NULL. For non-NULL operands, evaluates to 1 if an odd number of operands is non-zero, otherwise 0 is returned.

Examples

SELECT 1 XOR 1;
+---------+
| 1 XOR 1 |
+---------+
|       0 |
+---------+

SELECT 1 XOR 0;
+---------+
| 1 XOR 0 |
+---------+
|       1 |
+---------+

SELECT 1 XOR NULL;
+------------+
| 1 XOR NULL |
+------------+
|       NULL |
+------------+

In the following example, the right 1 XOR 1 is evaluated first, and returns 0. Then, 1 XOR 0 is evaluated, and 1 is returned.

SELECT 1 XOR 1 XOR 1;
+---------------+
| 1 XOR 1 XOR 1 |
+---------------+
|             1 |
+---------------+

1.1.5.5.4 ||

Syntax

OR, ||

Contents

  1. Syntax
  2. Description
    1. Oracle Mode
  3. Examples
  4. See Also

Description

Logical OR. When both operands are non-NULL, the result is 1 if any operand is non-zero, and 0 otherwise. With a NULL operand, the result is 1 if the other operand is non-zero, and NULL otherwise. If both operands are NULL, the result is NULL.

For this operator, short-circuit evaluation can be used.

Note that, if the PIPES_AS_CONCAT SQL_MODE is set, || is used as a string concatenation operator. This means that a || b is the same as CONCAT(a,b). See CONCAT() for details.

Oracle Mode

MariaDB starting with 10.3

In Oracle mode from MariaDB 10.3, || ignores NULL.

Examples

SELECT 1 || 1;
+--------+
| 1 || 1 |
+--------+
|      1 |
+--------+

SELECT 1 || 0;
+--------+
| 1 || 0 |
+--------+
|      1 |
+--------+

SELECT 0 || 0;
+--------+
| 0 || 0 |
+--------+
|      0 |
+--------+

SELECT 0 || NULL;
+-----------+
| 0 || NULL |
+-----------+
|      NULL |
+-----------+

SELECT 1 || NULL;
+-----------+
| 1 || NULL |
+-----------+
|         1 |
+-----------+

In Oracle mode, from MariaDB 10.3:

SELECT 0 || NULL;
+-----------+
| 0 || NULL |
+-----------+
| 0         |
+-----------+

See Also

1.1.5.6 Operator Precedence

The precedence is the order in which the SQL operators are evaluated.

The following list shows the SQL operator precedence. Operators that appear first in the list have a higher precedence. Operators which are listed together have the same precedence.

Functions precedence is always higher than operators precedence.

In this page CASE refers to the CASE operator, not to the CASE statement.

If the HIGH_NOT_PRECEDENCE SQL_MODE is set, NOT has the same precedence as !.

The || operator's precedence, as well as its meaning, depends on the PIPES_AS_CONCAT SQL_MODE flag: if it is on, || can be used to concatenate strings (like the CONCAT() function) and has a higher precedence.

The = operator's precedence depends on the context - it is higher when = is used as a comparison operator.

Parenthesis can be used to modify the operators precedence in an expression.

Short-circuit evaluation

The AND, OR, && and || operators support short-circuit evaluation. This means that, in some cases, the expression on the right of those operators is not evaluated, because its result cannot affect the result. In the following cases, short-circuit evaluation is used and x() is not evaluated:

  • FALSE AND x()
  • FALSE && x()
  • TRUE OR x()
  • TRUE || x()
  • NULL BETWEEN x() AND x()

Note however that the short-circuit evaluation does not apply to NULL AND x(). Also, BETWEEN's right operands are not evaluated if the left operand is NULL, but in all other cases all the operands are evaluated.

This is a speed optimization. Also, since functions can have side-effects, this behavior can be used to choose whether execute them or not using a concise syntax:

SELECT some_function() OR log_error();

1.1.6 Sequences

MariaDB starting with 10.3

CREATE SEQUENCE was introduced in MariaDB 10.3.

A sequence is an object that generates a sequence of numeric values, as specified by the CREATE SEQUENCE statement. Sequences are an alternative to AUTO_INCREMENT when you want more control over how sequence numbers are generated.

Since a SEQUENCE caches values, it can sometimes be faster. Also, you can access the last value generated by all used sequences; it's not subjected to limitations of LAST_INSERT_ID( ).

This section is about sequence objects. For details about the storage engine, see Sequence Storage Engine.

1.1.6.1 Sequence Overview

MariaDB starting with 10.3

Sequences were introduced in MariaDB 10.3.

Contents

  1. Introduction
  2. Creating a Sequence
  3. Using Sequence Objects
    1. Using Sequences in DEFAULT
  4. Changing a Sequence
  5. Dropping a Sequence
  6. Replication
  7. Standards Compliance
  8. Notes
  9. Table Operations that Work with Sequences
  10. Implementation
  11. Underlying Table Structure
  12. Credits
  13. See Also

Introduction

A sequence is an object that generates a sequence of numeric values, as specified by the CREATE SEQUENCE statement.

CREATE SEQUENCE will create a sequence that generates new values when called with NEXT VALUE FOR sequence_name. It's an alternative to AUTO INCREMENT when one wants to have more control of how the numbers are generated. As the SEQUENCE caches values (up to the CACHE value in the CREATE SEQUENCE statement, by default 1000) it can in some cases be much faster than AUTO INCREMENT. Another benefit is that one can access the last value generated by all used sequences, which solves one of the limitations with LAST_INSERT_ID().

Creating a Sequence

The CREATE SEQUENCE statement is used to create a sequence. Here is an example of a sequence starting at 100, incrementing by 10 each time:

CREATE SEQUENCE s START WITH 100 INCREMENT BY 10;

The CREATE SEQUENCE statement, along with defaults, can be viewd with the SHOW CREATE SEQUENCE STATEMENT, for example:

SHOW CREATE SEQUENCE s\G
*************************** 1. row ***************************
       Table: s
Create Table: CREATE SEQUENCE `s` start with 100 minvalue 1 maxvalue 9223372036854775806 
  increment by 10 cache 1000 nocycle ENGINE=InnoDB

Using Sequence Objects

To get the next value from a sequence, use

NEXT VALUE FOR sequence_name

or

NEXTVAL(sequence_name)

or in Oracle mode (SQL_MODE=ORACLE)

sequence_name.nextval

For retrieving the last value used by the current connection from a sequence use:

PREVIOUS VALUE FOR sequence_name

or

LASTVAL(sequence_name)

or in Oracle mode (SQL_MODE=ORACLE)

sequence_name.currval

For example:

SELECT NEXTVAL(s);
+------------+
| NEXTVAL(s) |
+------------+
|        100 |
+------------+

SELECT NEXTVAL(s);
+------------+
| NEXTVAL(s) |
+------------+
|        110 |
+------------+

SELECT LASTVAL(s);
+------------+
| LASTVAL(s) |
+------------+
|        110 |
+------------+

Using Sequences in DEFAULT

MariaDB starting with 10.3.3

Starting from 10.3.3 you can use Sequences in DEFAULT:

create sequence s1;
create table t1 (a int primary key default (next value for s1), b int);
insert into t1 (b) values (1),(2);
select * from t1;
+---+------+
| a | b    |
+---+------+
| 1 |    1 |
| 2 |    2 |
+---+------+

Changing a Sequence

The ALTER SEQUENCE statement is used for changing sequences. For example, to restart the sequence at another value:

ALTER SEQUENCE s RESTART 50;

SELECT NEXTVAL(s);
+------------+
| NEXTVAL(s) |
+------------+
|         50 |
+------------+

The SETVAL function can also be used to set the next value to be returned for a SEQUENCE, for example:

SELECT SETVAL(s, 100);
+----------------+
| SETVAL(s, 100) |
+----------------+
|            100 |
+----------------+

SETVAL can only be used to increase the sequence value. Attempting to set a lower value will fail, returning NULL:

SELECT SETVAL(s, 50);
+---------------+
| SETVAL(s, 50) |
+---------------+
|          NULL |
+---------------+

Dropping a Sequence

The DROP SEQUENCE statement is used to drop a sequence, for example:

DROP SEQUENCE s;

Replication

If one wants to use Sequences in a master-master setup or with Galera one should use INCREMENT=0. This will tell the Sequence to use auto_increment_increment and auto_increment_offset to generate unique values for each server.

Standards Compliance

MariaDB 10.3 supports both ANSI SQL and Oracle syntax for sequences.

However as SEQUENCE is implemented as a special kind of table, it uses the same namespace as tables. The benefits are that sequences show up in SHOW TABLES, and one can also create a sequence with CREATE TABLE and drop it with DROP TABLE. One can SELECT from it as from any other table. This ensures that all old tools that work with tables should work with sequences.

Since sequence objects act as regular tables in many contexts, they will be affected by LOCK TABLES. This is not the case in other DBMS, such as Oracle, where LOCK TABLE does not affect sequences.

Notes

One of the goals with the Sequence implementation is that all old tools, such as mysqldump, should work unchanged, while still keeping the normal usage of sequence standard compatibly.

To make this possible, sequence is currently implemented as a table with a few exclusive properties.

The special properties for sequence tables are:

  • A sequence table has always one row.
  • When one creates a sequence, either with CREATE TABLE or CREATE SEQUENCE, one row will be inserted.
  • If one tries to insert into a sequence table, the single row will be updated. This allows mysqldump to work but also gives the additional benefit that one can change all properties of a sequence with a single insert. New applications should of course also use ALTER SEQUENCE.
  • UPDATE or DELETE can't be performed on Sequence objects.
  • Doing a select on the sequence shows the current state of the sequence, except the values that are reserved in the cache. The next_value column shows the next value not reserved by the cache.
  • FLUSH TABLES will close the sequence and the next sequence number generated will be according to what's stored in the Sequence object. In effect, this will discard the cached values.
  • A number of normal table operations work on Sequence tables. See next section.

Table Operations that Work with Sequences

Implementation

Internally, sequence tables are created as a normal table without rollback (the InnoDB, Aria and MySAM engines support this), wrapped by a sequence engine object. This allowed us to create sequences with almost no performance impact for normal tables. (The cost is one 'if' per insert if the binary log is enabled).

Underlying Table Structure

The following example shows the table structure of sequences and how it can be used as a table. (Output of results are slightly edited to make them easier to read)

create sequence t1;
show create sequence t1\G
***** 1. row *****
  CREATE SEQUENCE `t1` start with 1 minvalue 1 maxvalue 9223372036854775806
  increment by 1 cache 1000 nocycle ENGINE=InnoDB


show create table t1\G
***** 1. row *****
Create Table: CREATE TABLE `t1` (
  `next_not_cached_value` bigint(21) NOT NULL,
  `minimum_value` bigint(21) NOT NULL,
  `maximum_value` bigint(21) NOT NULL,
  `start_value` bigint(21) NOT NULL COMMENT 'start value when sequences is created or value if RESTART is used',
  `increment` bigint(21) NOT NULL COMMENT 'increment value',
  `cache_size` bigint(21) unsigned NOT NULL,
  `cycle_option` tinyint(1) unsigned NOT NULL COMMENT '0 if no cycles are allowed, 1 if the sequence should begin a new cycle when maximum_value is passed',
  `cycle_count` bigint(21) NOT NULL COMMENT 'How many cycles have been done'
) ENGINE=InnoDB SEQUENCE=1


select * from t1\G
next_not_cached_value: 1
 minimum_value: 1
 maximum_value: 9223372036854775806
  start_value: 1
  increment: 1
  cache_size: 1000
  cycle_option: 0
  cycle_count: 0

The cycle_count column is incremented every time the sequence wraps around.

Credits

  • Thanks to Jianwe Zhao from Aliyun for his work on SEQUENCE in AliSQL, which gave ideas and inspiration for this work.
  • Thanks to Peter Gulutzan,who helped test and gave useful comments about the implementation.

See Also

1.1.6.2 CREATE SEQUENCE

MariaDB starting with 10.3

CREATE SEQUENCE was introduced in MariaDB 10.3.

Syntax

CREATE [OR REPLACE] [TEMPORARY] SEQUENCE [IF NOT EXISTS] sequence_name
[ INCREMENT [ BY | = ] increment ]
[ MINVALUE [=] minvalue | NO MINVALUE | NOMINVALUE ]
[ MAXVALUE [=] maxvalue | NO MAXVALUE | NOMAXVALUE ]
[ START [ WITH | = ] start ] 
[ CACHE [=] cache | NOCACHE ] [ CYCLE | NOCYCLE] 
[table_options]

Contents

  1. Syntax
  2. Description
    1. Arguments to Create
    2. Constraints on Create Arguments
    3. Atomic DDL
  3. Examples
  4. See Also

The options for CREATE SEQUENCE can be given in any order, optionally followed by table_options.

table_options can be any of the normal table options in CREATE TABLE but the most usable ones are ENGINE=... and COMMENT=.

NOMAXVALUE and NOMINVALUE are there to allow one to create SEQUENCEs using the Oracle syntax.

Description

CREATE SEQUENCE will create a sequence that generates new values when called with NEXT VALUE FOR sequence_name. It's an alternative to AUTO INCREMENT when one wants to have more control of how the numbers are generated. As the SEQUENCE caches values (up to CACHE) it can in some cases be much faster than AUTO INCREMENT. Another benefit is that one can access the last value generated by all used sequences, which solves one of the limitations with LAST_INSERT_ID().

CREATE SEQUENCE requires the CREATE privilege.

DROP SEQUENCE can be used to drop a sequence, and ALTER SEQUENCE to change it.

Arguments to Create

The following options may be used:

OptionDefault value Description
INCREMENT 1Increment to use for values. May be negative. Setting an increment of 0 causes the sequence to use the value of the auto_increment_increment system variable at the time of creation, which is always a positive number. (see MDEV-16035).
MINVALUE1 if INCREMENT > 0 and -9223372036854775807 if INCREMENT < 0Minimum value for the sequence
MAXVALUE9223372036854775806 if INCREMENT > 0 and -1 if INCREMENT < 0Max value for sequence
STARTMINVALUE if INCREMENT > 0 and MAX_VALUE if INCREMENT< 0First value that the sequence will generate
CACHE1000 Number of values that should be cached. 0 if no CACHE. The underlying table will be updated first time a new sequence number is generated and each time the cache runs out.

If CYCLE is used then the sequence should start again from MINVALUE after it has run out of values. Default value is NOCYCLE.

Constraints on Create Arguments

To be able to create a legal sequence, the following must hold:

  • MAXVALUE >= start
  • MAXVALUE > MINVALUE
  • START >= MINVALUE
  • MAXVALUE <= 9223372036854775806 (LONGLONG_MAX-1)
  • MINVALUE >= -9223372036854775807 (LONGLONG_MIN+1)

Note that sequences can't generate the maximum/minimum 64 bit number because of the constraint of MINVALUE and MAXVALUE.

Atomic DDL

MariaDB starting with 10.6.1

MariaDB 10.6.1 supports Atomic DDL and CREATE SEQUENCE is atomic.

Examples

CREATE SEQUENCE s START WITH 100 INCREMENT BY 10;

CREATE SEQUENCE s2 START WITH -100 INCREMENT BY -10;

The following statement fails, as the increment conflicts with the defaults

CREATE SEQUENCE s3 START WITH -100 INCREMENT BY 10;
ERROR 4082 (HY000): Sequence 'test.s3' values are conflicting

The sequence can be created by specifying workable minimum and maximum values:

CREATE SEQUENCE s3 START WITH -100 INCREMENT BY 10 MINVALUE=-100 MAXVALUE=1000;

See Also

1.1.6.3 SHOW CREATE SEQUENCE

1.1.6.4 ALTER SEQUENCE

MariaDB starting with 10.3.1

ALTER SEQUENCE was introduced in MariaDB 10.3.

Syntax

ALTER SEQUENCE [IF EXISTS] sequence_name
[ INCREMENT [ BY | = ] increment ]
[ MINVALUE [=] minvalue | NO MINVALUE | NOMINVALUE ]
[ MAXVALUE [=] maxvalue | NO MAXVALUE | NOMAXVALUE ]
[ START [ WITH | = ] start ] [ CACHE [=] cache ] [ [ NO ] CYCLE ]
[ RESTART [[WITH | =] restart]

Contents

  1. Syntax
  2. Description
    1. Arguments to ALTER SEQUENCE
    2. INSERT
    3. Notes
  3. See Also

ALTER SEQUENCE allows one to change any values for a SEQUENCE created with CREATE SEQUENCE.

The options for ALTER SEQUENCE can be given in any order.

Description

ALTER SEQUENCE changes the parameters of an existing sequence generator. Any parameters not specifically set in the ALTER SEQUENCE command retain their prior settings.

ALTER SEQUENCE requires the ALTER privilege.

Arguments to ALTER SEQUENCE

The following options may be used:

OptionDefault valueDescription
INCREMENT1Increment to use for values. May be negative.
MINVALUE1 if INCREMENT > 0 and -9223372036854775807 if INCREMENT < 0Minimum value for the sequence.
MAXVALUE9223372036854775806 if INCREMENT > 0 and -1 if INCREMENT < 0Max value for sequence.
STARTMINVALUE if INCREMENT > 0 and MAX_VALUE if INCREMENT< 0First value that the sequence will generate.
CACHE1000Number of values that should be cached. 0 if no CACHE. The underlying table will be updated first time a new sequence number is generated and each time the cache runs out.
CYCLE0 (= NO CYCLE)1 if the sequence should start again from MINVALUE# after it has run out of values.
RESTARTSTART if restart value not is given If RESTART option is used, NEXT VALUE will return the restart value.

The optional clause RESTART [ WITH restart ] sets the next value for the sequence. This is equivalent to calling the SETVAL() function with the is_used argument as 0. The specified value will be returned by the next call of nextval. Using RESTART with no restart value is equivalent to supplying the start value that was recorded by CREATE SEQUENCE or last set by ALTER SEQUENCE START WITH.

ALTER SEQUENCE will not allow you to change the sequence so that it's inconsistent. For example:

CREATE SEQUENCE s1;
ALTER SEQUENCE s1 MINVALUE 10;
ERROR 4061 (HY000): Sequence 'test.t1' values are conflicting

ALTER SEQUENCE s1 MINVALUE 10 RESTART 10;
ERROR 4061 (HY000): Sequence 'test.t1' values are conflicting

ALTER SEQUENCE s1 MINVALUE 10 START 10 RESTART 10;

INSERT

To allow SEQUENCE objects to be backed up by old tools, like mysqldump, one can use SELECT to read the current state of a SEQUENCE object and use an INSERT to update the SEQUENCE object. INSERT is only allowed if all fields are specified:

CREATE SEQUENCE s1;
INSERT INTO s1 VALUES(1000,10,2000,1005,1,1000,0,0);
SELECT * FROM s1;

+------------+-----------+-----------+-------+-----------+-------+-------+-------+
| next_value | min_value | max_value | start | increment | cache | cycle | round |
+------------+-----------+-----------+-------+-----------+-------+-------+-------+
|       1000 |        10 |      2000 |  1005 |         1 |  1000 |     0 |     0 |
+------------+-----------+-----------+-------+-----------+-------+-------+-------+

SHOW CREATE SEQUENCE s1;
+-------+--------------------------------------------------------------------------------------------------------------+
| Table | Create Table                                                                                                 |
+-------+--------------------------------------------------------------------------------------------------------------+
| s1    | CREATE SEQUENCE `s1` start with 1005 minvalue 10 maxvalue 2000 increment by 1 cache 1000 nocycle ENGINE=Aria |
+-------+--------------------------------------------------------------------------------------------------------------+

Notes

ALTER SEQUENCE will instantly affect all future SEQUENCE operations. This is in contrast to some other databases where the changes requested by ALTER SEQUENCE will not be seen until the sequence cache has run out.

ALTER SEQUENCE will take a full table lock of the sequence object during its (brief) operation. This ensures that ALTER SEQUENCE is replicated correctly. If you only want to set the next sequence value to a higher value than current, then you should use SETVAL() instead, as this is not blocking.

If you want to change storage engine, sequence comment or rename the sequence, you can use ALTER TABLE for this.

See Also

1.1.6.5 DROP SEQUENCE

MariaDB starting with 10.3

DROP SEQUENCE was introduced in MariaDB 10.3.

Syntax

DROP [TEMPORARY] SEQUENCE [IF EXISTS] [/*COMMENT TO SAVE*/]
    sequence_name [, sequence_name] ...

Contents

  1. Syntax
  2. Description
  3. Notes
  4. See Also

Description

DROP SEQUENCE removes one or more sequences created with CREATE SEQUENCE. You must have the DROP privilege for each sequence. MariaDB returns an error indicating by name which non-existing tables it was unable to drop, but it also drops all of the tables in the list that do exist.

Important: When a table is dropped, user privileges on the table are not automatically dropped. See GRANT.

If another connection is using the sequence, a metadata lock is active, and this statement will wait until the lock is released. This is also true for non-transactional tables.

For each referenced sequence, DROP SEQUENCE drops a temporary sequence with that name, if it exists. If it does not exist, and the TEMPORARY keyword is not used, it drops a non-temporary sequence with the same name, if it exists. The TEMPORARY keyword ensures that a non-temporary sequence will not accidentally be dropped.

Use IF EXISTS to prevent an error from occurring for sequences that do not exist. A NOTE is generated for each non-existent sequence when using IF EXISTS. See SHOW WARNINGS.

DROP SEQUENCE requires the DROP privilege.

Notes

DROP SEQUENCE only removes sequences, not tables. However, DROP TABLE can remove both sequences and tables.

See Also

1.1.6.6 SEQUENCE Functions

MariaDB starting with 10.3

SEQUENCEs were introduced in MariaDB 10.3.

Functions that can be used on SEQUENCEs

1.1.6.6.1 LASTVAL

LASTVAL is a synonym for PREVIOUS VALUE for sequence_name.

1.1.6.6.2 NEXT VALUE for sequence_name

MariaDB starting with 10.3

SEQUENCEs were introduced in MariaDB 10.3

Syntax

NEXT VALUE FOR sequence

or

NEXTVAL(sequence_name)

or in Oracle mode (SQL_MODE=ORACLE)

sequence_name.nextval

Contents

  1. Syntax
  2. Description
  3. See Also

NEXT VALUE FOR is ANSI SQL syntax while NEXTVAL() is PostgreSQL syntax.

Description

Generate next value for a SEQUENCE.

  • You can greatly speed up NEXT VALUE by creating the sequence with the CACHE option. If not, every NEXT VALUE usage will cause changes in the stored SEQUENCE table.
  • When using NEXT VALUE the value will be reserved at once and will not be reused, except if the SEQUENCE was created with CYCLE. This means that when you are using SEQUENCEs you have to expect gaps in the generated sequence numbers.
  • If one updates the SEQUENCE with SETVAL() or ALTER SEQUENCE ... RESTART, NEXT VALUE FOR will notice this and start from the next requested value.
  • FLUSH TABLES will close the sequence and the next sequence number generated will be according to what's stored in the SEQUENCE object. In effect, this will discard the cached values.
  • A server restart (or closing the current connection) also causes a drop of all cached values. The cached sequence numbers are reserved only for the current connection.
  • NEXT VALUE requires the INSERT privilege.
MariaDB starting with 10.3.3
  • You can also use NEXT VALUE FOR sequence for column DEFAULT.

See Also

1.1.6.6.3 NEXTVAL

NEXTVAL is a synonym for NEXT VALUE for sequence_name.

1.1.6.6.4 PREVIOUS VALUE FOR sequence_name

MariaDB starting with 10.3

SEQUENCEs were introduced in MariaDB 10.3.

Syntax

PREVIOUS VALUE FOR sequence_name

or

LASTVAL(sequence_name)

or in Oracle mode (SQL_MODE=ORACLE)

sequence_name.currval

Contents

  1. Syntax
  2. Description
  3. Example
  4. See Also

PREVIOUS VALUE FOR is IBM DB2 syntax while LASTVAL() is PostgreSQL syntax.

Description

Get last value in the current connection generated from a sequence.

  • If the sequence has not yet been used by the connection, PREVIOUS VALUE FOR returns NULL (the same thing applies with a new connection which doesn't see a last value for an existing sequence).
  • If a SEQUENCE has been dropped and re-created then it's treated as a new SEQUENCE and PREVIOUS VALUE FOR will return NULL.
  • FLUSH TABLES has no effect on PREVIOUS VALUE FOR.
  • Previous values for all used sequences are stored per connection until connection ends.
  • PREVIOUS VALUE FOR requires the SELECT privilege.

Example

MariaDB [test]> CREATE SEQUENCE s START WITH 100 INCREMENT BY 10;
Query OK, 0 rows affected (0.026 sec)

MariaDB [test]> SELECT PREVIOUS VALUE FOR s;
+----------------------+
| PREVIOUS VALUE FOR s |
+----------------------+
|                 NULL |
+----------------------+
1 row in set (0.000 sec)

# The function works for sequences only, if the table is used an error is generated
MariaDB [test]> SELECT PREVIOUS VALUE FOR t;
ERROR 4089 (42S02): 'test.t' is not a SEQUENCE

# Call the NEXT VALUE FOR s:
MariaDB [test]> SELECT NEXT VALUE FOR s;
+------------------+
| NEXT VALUE FOR s |
+------------------+
|              100 |
+------------------+
1 row in set (0.000 sec)

MariaDB [test]> SELECT PREVIOUS VALUE FOR s;
+----------------------+
| PREVIOUS VALUE FOR s |
+----------------------+
|                  100 |
+----------------------+
1 row in set (0.000 sec)

Now try to start the new connection and check that the last value is still NULL, before updating the value in the new connection after the output of the new connection gets current value (110 in the example below). Note that first connection cannot see this change and the result of last value still remains the same (100 in the example above).

$ .mysql -uroot test -e"SELECT PREVIOUS VALUE FOR s; SELECT NEXT VALUE FOR s; SELECT PREVIOUS VALUE FOR s;"
+----------------------+
| PREVIOUS VALUE FOR s |
+----------------------+
|                 NULL |
+----------------------+
+------------------+
| NEXT VALUE FOR s |
+------------------+
|              110 |
+------------------+
+----------------------+
| PREVIOUS VALUE FOR s |
+----------------------+
|                  110 |
+----------------------+

See Also

1.1.6.6.5 SETVAL()

MariaDB starting with 10.3.1

SEQUENCEs were introduced in MariaDB 10.3.

Syntax

SETVAL(sequence_name, next_value, [is_used, [round]])

Contents

  1. Syntax
  2. Description
  3. Examples
  4. See Also

Description

Set the next value to be returned for a SEQUENCE.

This function is compatible with PostgreSQL syntax, extended with the round argument.

If the is_used argument is not given or is 1 or true, then the next used value will one after the given value. If is_used is 0 or false then the next generated value will be the given value.

If round is used then it will set the round value (or the internal cycle count, starting at zero) for the sequence. If round is not used, it's assumed to be 0.

next_value must be an integer literal.

For SEQUENCE tables defined with CYCLE (see CREATE SEQUENCE) one should use both next_value and round to define the next value. In this case the current sequence value is defined to be round, next_value.

The result returned by SETVAL() is next_value or NULL if the given next_value and round is smaller than the current value.

SETVAL() will not set the SEQUENCE value to a something that is less than its current value. This is needed to ensure that SETVAL() is replication safe. If you want to set the SEQUENCE to a smaller number use ALTER SEQUENCE.

If CYCLE is used, first round and then next_value are compared to see if the value is bigger than the current value.

Internally, in the MariaDB server, SETVAL() is used to inform slaves that a SEQUENCE has changed value. The slave may get SETVAL() statements out of order, but this is ok as only the biggest one will have an effect.

SETVAL requires the INSERT privilege.

Examples

SELECT setval(foo, 42);           -- Next nextval will return 43
SELECT setval(foo, 42, true);     -- Same as above
SELECT setval(foo, 42, false);    -- Next nextval will return 42

SETVAL setting higher and lower values on a sequence with an increment of 10:

SELECT NEXTVAL(s);
+------------+
| NEXTVAL(s) |
+------------+
|         50 |
+------------+

SELECT SETVAL(s, 100);
+----------------+
| SETVAL(s, 100) |
+----------------+
|            100 |
+----------------+

SELECT NEXTVAL(s);
+------------+
| NEXTVAL(s) |
+------------+
|        110 |
+------------+

SELECT SETVAL(s, 50);
+---------------+
| SETVAL(s, 50) |
+---------------+
|          NULL |
+---------------+

SELECT NEXTVAL(s);
+------------+
| NEXTVAL(s) |
+------------+
|        120 |
+------------+

Example demonstrating round:

CREATE OR REPLACE SEQUENCE s1
  START WITH 1
  MINVALUE 1
  MAXVALUE 99
  INCREMENT BY 1 
  CACHE 20 
  CYCLE;

SELECT SETVAL(s1, 99, 1, 0);
+----------------------+
| SETVAL(s1, 99, 1, 0) |
+----------------------+
|                   99 |
+----------------------+

SELECT NEXTVAL(s1);
+-------------+
| NEXTVAL(s1) |
+-------------+
|           1 |
+-------------+

The following statement returns NULL, as the given next_value and round is smaller than the current value.

SELECT SETVAL(s1, 99, 1, 0);
+----------------------+
| SETVAL(s1, 99, 1, 0) |
+----------------------+
|                 NULL |
+----------------------+

SELECT NEXTVAL(s1);
+-------------+
| NEXTVAL(s1) |
+-------------+
|           2 |
+-------------+

Increasing the round from zero to 1 will allow next_value to be returned.

SELECT SETVAL(s1, 99, 1, 1);
+----------------------+
| SETVAL(s1, 99, 1, 1) |
+----------------------+
|                   99 |
+----------------------+

SELECT NEXTVAL(s1);
+-------------+
| NEXTVAL(s1) |
+-------------+
|           1 |
+-------------+

See Also

1.1.6.7 SHOW TABLES

1.1.7 Temporal Tables

MariaDB supports temporal data tables in the form of system-versioning tables (allowing you to query and operate on historic data), application-time periods (allow you to query and operate on a temporal range of data), and bitemporal tables (which combine both system-versioning and application-time periods).

1.1.7.1 System-Versioned Tables

Contents

  1. System-Versioned Tables
    1. Creating a System-Versioned Table
    2. Adding or Removing System Versioning To/From a Table
    3. Querying Historical Data
      1. SELECT
      2. Views and Subqueries
      3. Use in Replication and Binary Logs
    4. Transaction-Precise History in InnoDB
    5. Storing the History Separately
      1. Default Partitions
    6. Removing Old History
    7. Excluding Columns From Versioning
  2. System Variables
    1. system_versioning_alter_history
    2. system_versioning_asof
    3. system_versioning_innodb_algorithm_simple
  3. Limitations
  4. See Also

MariaDB supports temporal data tables in the form of system-versioning tables (allowing you to query and operate on historic data, discussed below), application-time periods (allow you to query and operate on a temporal range of data), and bitemporal tables (which combine both system-versioning and application-time periods).

System-Versioned Tables


MariaDB starting with 10.3.4

Support for system-versioned tables was added in MariaDB 10.3.4.

System-versioned tables store the history of all changes, not only data which is currently valid. This allows data analysis for any point in time, auditing of changes and comparison of data from different points in time. Typical uses cases are:

  • Forensic analysis & legal requirements to store data for N years.
  • Data analytics (retrospective, trends etc.), e.g. to get your staff information as of one year ago.
  • Point-in-time recovery - recover a table state as of particular point in time.

System-versioned tables were first introduced in the SQL:2011 standard.

Creating a System-Versioned Table


The CREATE TABLE syntax has been extended to permit creating a system-versioned table. To be system-versioned, according to SQL:2011, a table must have two generated columns, a period, and a special table option clause: 

CREATE TABLE t(
   x INT,
   start_timestamp TIMESTAMP(6) GENERATED ALWAYS AS ROW START,
   end_timestamp TIMESTAMP(6) GENERATED ALWAYS AS ROW END,
   PERIOD FOR SYSTEM_TIME(start_timestamp, end_timestamp)
) WITH SYSTEM VERSIONING;

In MariaDB one can also use a simplified syntax:

CREATE TABLE t (
   x INT
) WITH SYSTEM VERSIONING;

In the latter case no extra columns will be created and they won't clutter the output of, say, SELECT * FROM t. The versioning information will still be stored, and it can be accessed via the pseudo-columns ROW_START and ROW_END:

SELECT x, ROW_START, ROW_END FROM t;

Adding or Removing System Versioning To/From a Table

An existing table can be altered to enable system versioning for it.

CREATE TABLE t(
  x INT
);

ALTER TABLE t ADD SYSTEM VERSIONING;

SHOW CREATE TABLE t\G
*************************** 1. row ***************************
       Table: t
Create Table: CREATE TABLE `t` (
  `x` int(11) DEFAULT NULL
) ENGINE=InnoDB DEFAULT CHARSET=latin1 WITH SYSTEM VERSIONING

Similarly, system versioning can be removed from a table:

ALTER TABLE t DROP SYSTEM VERSIONING;

SHOW CREATE TABLE t\G
*************************** 1. row ***************************
       Table: t
Create Table: CREATE TABLE `t` (
  `x` int(11) DEFAULT NULL
) ENGINE=InnoDB DEFAULT CHARSET=latin1

One can also add system versioning with all columns created explicitly:

ALTER TABLE t ADD COLUMN ts TIMESTAMP(6) GENERATED ALWAYS AS ROW START,
              ADD COLUMN te TIMESTAMP(6) GENERATED ALWAYS AS ROW END,
              ADD PERIOD FOR SYSTEM_TIME(ts, te),
              ADD SYSTEM VERSIONING;

SHOW CREATE TABLE t\G
*************************** 1. row ***************************
       Table: t
Create Table: CREATE TABLE `t` (
  `x` int(11) DEFAULT NULL,
  `ts` timestamp(6) GENERATED ALWAYS AS ROW START,
  `te` timestamp(6) GENERATED ALWAYS AS ROW END,
  PERIOD FOR SYSTEM_TIME (`ts`, `te`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1 WITH SYSTEM VERSIONING

Querying Historical Data

SELECT

To query the historical data one uses the clause FOR SYSTEM_TIME directly after the table name (before the table alias, if any). SQL:2011 provides three syntactic extensions:

  • AS OF is used to see the table as it was at a specific point in time in the past: 
SELECT * FROM t FOR SYSTEM_TIME AS OF TIMESTAMP'2016-10-09 08:07:06';
  • BETWEEN start AND end will show all rows that were visible at any point between two specified points in time. It works inclusively, a row visible exactly at start or exactly at end will be shown too. 
SELECT * FROM t FOR SYSTEM_TIME BETWEEN (NOW() - INTERVAL 1 YEAR) AND NOW();
  • FROM start TO end will also show all rows that were visible at any point between two specified points in time, including start, but excluding end. 
SELECT * FROM t FOR SYSTEM_TIME FROM '2016-01-01 00:00:00' TO '2017-01-01 00:00:00';

Additionally MariaDB implements a non-standard extension:

  • ALL will show all rows, historical and current. 
SELECT * FROM t FOR SYSTEM_TIME ALL;

If the FOR SYSTEM_TIME clause is not used, the table will show the current data, as if one had specified FOR SYSTEM_TIME AS OF CURRENT_TIMESTAMP.

Views and Subqueries

When a system-versioned tables is used in a view or in a subquery in the from clause, FOR SYSTEM_TIME can be used directly in the view or subquery body, or (non-standard) applied to the whole view when it's being used in a SELECT:

CREATE VIEW v1 AS SELECT * FROM t FOR SYSTEM_TIME AS OF TIMESTAMP'2016-10-09 08:07:06';

Or

CREATE VIEW v1 AS SELECT * FROM t;
SELECT * FROM v1 FOR SYSTEM_TIME AS OF TIMESTAMP'2016-10-09 08:07:06';

Use in Replication and Binary Logs

Tables that use system-versioning implicitly add the row_end column to the Primary Key. While this is generally not an issue for most use cases, it can lead to problems when re-applying write statements from the binary log or in replication environments, where a primary retries an SQL statement on the replica.

Specifically, these writes include a value on the row_end column containing the timestamp from when the write was initially made. The re-occurrence of the Primary Key with the old system-versioning columns raises an error due to the duplication.

To mitigate this with MariaDB Replication, set the secure_timestamp system variable to YES on the replica. When set, the replica uses its own system clock when applying to the row log, meaning that the primary can retry as many times as needed without causing a conflict. The retries generate new historical rows with new values for the row_start and row_end columns.

Transaction-Precise History in InnoDB

A point in time when a row was inserted or deleted does not necessarily mean that a change became visible at the same moment. With transactional tables, a row might have been inserted in a long transaction, and became visible hours after it was inserted.

For some applications — for example, when doing data analytics on one-year-old data — this distinction does not matter much. For others — forensic analysis — it might be crucial.

MariaDB supports transaction-precise history (only for the InnoDB storage engine) that allows seeing the data exactly as it would've been seen by a new connection doing a SELECT at the specified point in time — rows inserted before that point, but committed after will not be shown.

To use transaction-precise history, InnoDB needs to remember not timestamps, but transaction identifier per row. This is done by creating generated columns as BIGINT UNSIGNED, not TIMESTAMP(6):

CREATE TABLE t(
   x INT,
   start_trxid BIGINT UNSIGNED GENERATED ALWAYS AS ROW START,
   end_trxid BIGINT UNSIGNED GENERATED ALWAYS AS ROW END,
   PERIOD FOR SYSTEM_TIME(start_trxid, end_trxid)
) WITH SYSTEM VERSIONING;

These columns must be specified explicitly, but they can be made INVISIBLE to avoid cluttering SELECT * output.

When one uses transaction-precise history, one can optionally use transaction identifiers in the FOR SYSTEM_TIME clause:

SELECT * FROM t FOR SYSTEM_TIME AS OF TRANSACTION 12345;

This will show the data, exactly as it was seen by the transaction with the identifier 12345.

Storing the History Separately

When the history is stored together with the current data, it increases the size of the table, so current data queries — table scans and index searches — will take more time, because they will need to skip over historical data. If most queries on that table use only current data, it might make sense to store the history separately, to reduce the overhead from versioning.

This is done by partitioning the table by SYSTEM_TIME. Because of the partition pruning optimization, all current data queries will only access one partition, the one that stores current data.

This example shows how to create such a partitioned table:

CREATE TABLE t (x INT) WITH SYSTEM VERSIONING
  PARTITION BY SYSTEM_TIME (
    PARTITION p_hist HISTORY,
    PARTITION p_cur CURRENT
  );

In this example all history will be stored in the partition p_hist while all current data will be in the partition p_cur. The table must have exactly one current partition and at least one historical partition.

Partitioning by SYSTEM_TIME also supports automatic partition rotation. One can rotate historical partitions by time or by size. This example shows how to rotate partitions by size:

CREATE TABLE t (x INT) WITH SYSTEM VERSIONING
  PARTITION BY SYSTEM_TIME LIMIT 100000 (
    PARTITION p0 HISTORY,
    PARTITION p1 HISTORY,
    PARTITION pcur CURRENT
  );

MariaDB will start writing history rows into partition p0, and when it reaches a size of 100000 rows, MariaDB will switch to partition p1. There are only two historical partitions, so when p1 overflows, MariaDB will issue a warning, but will continue writing into it.

Similarly, one can rotate partitions by time:

CREATE TABLE t (x INT) WITH SYSTEM VERSIONING
  PARTITION BY SYSTEM_TIME INTERVAL 1 WEEK (
    PARTITION p0 HISTORY,
    PARTITION p1 HISTORY,
    PARTITION p2 HISTORY,
    PARTITION pcur CURRENT
  );

This means that the history for the first week after the table was created will be stored in p0. The history for the second week — in p1, and all later history will go into p2. One can see the exact rotation time for each partition in the INFORMATION_SCHEMA.PARTITIONS table.

It is possible to combine partitioning by SYSTEM_TIME and subpartitions:

CREATE TABLE t (x INT) WITH SYSTEM VERSIONING
  PARTITION BY SYSTEM_TIME
    SUBPARTITION BY KEY (x)
    SUBPARTITIONS 4 (
    PARTITION ph HISTORY,
    PARTITION pc CURRENT
  );

Default Partitions

MariaDB starting with 10.5.0

Since partitioning by current and historical data is such a typical usecase, from MariaDB 10.5, it is possible to use a simplified statement to do so. For example, instead of

CREATE TABLE t (x INT) WITH SYSTEM VERSIONING 
  PARTITION BY SYSTEM_TIME (
    PARTITION p0 HISTORY,  
    PARTITION pn CURRENT 
);

you can use

CREATE TABLE t (x INT) WITH SYSTEM VERSIONING 
  PARTITION BY SYSTEM_TIME;

You can also specify the number of partitions, which is useful if you want to rotate history by time, for example:

CREATE TABLE t (x INT) WITH SYSTEM VERSIONING 
  PARTITION BY SYSTEM_TIME 
    INTERVAL 1 MONTH 
    PARTITIONS 12;

Specifying the number of partitions without specifying a rotation condition will result in a warning:

CREATE OR REPLACE TABLE t (x INT) WITH SYSTEM VERSIONING
  PARTITION BY SYSTEM_TIME PARTITIONS 12;
Query OK, 0 rows affected, 1 warning (0.518 sec)

Warning (Code 4115): Maybe missing parameters: no rotation condition for multiple HISTORY partitions.

while specifying only 1 partition will result in an error:

CREATE OR REPLACE TABLE t (x INT) WITH SYSTEM VERSIONING
  PARTITION BY SYSTEM_TIME PARTITIONS 1;
ERROR 4128 (HY000): Wrong partitions for `t`: must have at least one HISTORY and exactly one last CURRENT

Removing Old History

Because it stores all the history, a system-versioned table might grow very large over time. There are many options to trim down the space and remove the old history.

One can completely drop the versioning from the table and add it back again, this will delete all the history:

ALTER TABLE t DROP SYSTEM VERSIONING;
ALTER TABLE t ADD SYSTEM VERSIONING;

It might be a rather time-consuming operation, though, as the table will need to be rebuilt, possibly twice (depending on the storage engine).

Another option would be to use partitioning and drop some of historical partitions:

ALTER TABLE t DROP PARTITION p0;

Note, that one cannot drop a current partition or the only historical partition.

And the third option; one can use a variant of the DELETE statement to prune the history:

DELETE HISTORY FROM t;

or only old history up to a specific point in time:

DELETE HISTORY FROM t BEFORE SYSTEM_TIME '2016-10-09 08:07:06';

or to a specific transaction (with BEFORE SYSTEM_TIME TRANSACTION xxx).

To protect the integrity of the history, this statement requires a special DELETE HISTORY privilege.

The TRUNCATE TABLE statement drops all historical records from a system-versioned-table.

Currently, using the DELETE HISTORY statement with a BEFORE SYSTEM_TIME greater than the ROW_END of the active records (as a TIMESTAMP, this has a maximum value of '2038-01-19 03:14:07' UTC) will result in the historical records being dropped, and the active records being deleted and moved to history. See MDEV-25468.

Excluding Columns From Versioning

Another MariaDB extension allows to version only a subset of columns in a table. This is useful, for example, if you have a table with user information that should be versioned, but one column is, let's say, a login counter that is incremented often and is not interesting to version. Such a column can be excluded from versioning by declaring it WITHOUT VERSIONING

CREATE TABLE t (
   x INT,
   y INT WITHOUT SYSTEM VERSIONING
) WITH SYSTEM VERSIONING;

A column can also be declared WITH VERSIONING, that will automatically make the table versioned. The statement below is equivalent to the one above:

CREATE TABLE t (
   x INT WITH SYSTEM VERSIONING,
   y INT
);

System Variables

There are a number of system variables related to system-versioned tables:

system_versioning_alter_history

  • Description: SQL:2011 does not allow ALTER TABLE on system-versioned tables. When this variable is set to ERROR, an attempt to alter a system-versioned table will result in an error. When this variable is set to KEEP, ALTER TABLE will be allowed, but the history will become incorrect — querying historical data will show the new table structure. This mode is still useful, for example, when adding new columns to a table. Note that if historical data contains or would contain nulls, attempting to ALTER these columns to be NOT NULL will return an error (or warning if strict_mode is not set).
  • Commandline: --system-versioning-alter-history=value
  • Scope: Global, Session
  • Dynamic: Yes
  • Type: Enum
  • Default Value: ERROR
  • Valid Values: ERROR, KEEP
  • Introduced: MariaDB 10.3.4

system_versioning_asof

  • Description: If set to a specific timestamp value, an implicit FOR SYSTEM_TIME AS OF clause will be applied to all queries. This is useful if one wants to do many queries for history at the specific point in time. Set it to DEFAULT to restore the default behavior. Has no effect on DML, so queries such as INSERT .. SELECT and REPLACE .. SELECT need to state AS OF explicitly.
  • Commandline: None
  • Scope: Global, Session
  • Dynamic: Yes
  • Type: Varchar
  • Default Value: DEFAULT
  • Introduced: MariaDB 10.3.4

system_versioning_innodb_algorithm_simple

  • Description: Never fully implemented and removed in the following release.
  • Commandline: --system-versioning-innodb-algorithm-simple[={0|1}]
  • Scope: Global, Session
  • Dynamic: Yes
  • Type: Boolean
  • Default Value: ON
  • Introduced: MariaDB 10.3.4
  • Removed: MariaDB 10.3.5

Limitations

  • Versioning clauses can not be applied to generated (virtual and persistent) columns.
  • mysqldump does not read historical rows from versioned tables, and so historical data will not be backed up. Also, a restore of the timestamps would not be possible as they cannot be defined by an insert/a user.

See Also

1.1.7.2 Application-Time Periods

Contents

  1. Creating Tables with Time Periods
  2. Adding and Removing Time Periods
  3. Deletion by Portion
  4. Updating by Portion
  5. WITHOUT OVERLAPS
  6. Further Examples
  7. See Also
MariaDB starting with 10.4.3

Support for application-time period-versioning was added in MariaDB 10.4.3.

Extending system-versioned tables, MariaDB 10.4 supports application-time period tables. Time periods are defined by a range between two temporal columns. The columns must be of the same temporal data type, i.e. DATE, TIMESTAMP or DATETIME (TIME and YEAR are not supported), and of the same width.

Using time periods implicitly defines the two columns as NOT NULL. It also adds a constraint to check whether the first value is less than the second value. The constraint is invisible to SHOW CREATE TABLE statements. The name of this constraint is prefixed by the time period name, to avoid conflict with other constraints.

Creating Tables with Time Periods

To create a table with a time period, use a CREATE TABLE statement with the PERIOD table option.

CREATE TABLE t1(
   name VARCHAR(50), 
   date_1 DATE,
   date_2 DATE,
   PERIOD FOR date_period(date_1, date_2));

This creates a table with a time_period period and populates the table with some basic temporal values.

Examples are available in the MariaDB Server source code, at mysql-test/suite/period/r/create.result.

Adding and Removing Time Periods

The ALTER TABLE statement now supports syntax for adding and removing time periods from a table. To add a period, use the ADD PERIOD clause.

For example:

CREATE OR REPLACE TABLE rooms (
 room_number INT,
 guest_name VARCHAR(255),
 checkin DATE,
 checkout DATE
 );

ALTER TABLE rooms ADD PERIOD FOR p(checkin,checkout);

To remove a period, use the DROP PERIOD clause:

ALTER TABLE rooms DROP PERIOD FOR p;

Both ADD PERIOD and DROP PERIOD clauses include an option to handle whether the period already exists:

ALTER TABLE rooms ADD PERIOD IF NOT EXISTS FOR p(checkin,checkout);

ALTER TABLE rooms DROP PERIOD IF EXISTS FOR p;

Deletion by Portion

You can also remove rows that fall within certain time periods.

When MariaDB executes a DELETE FOR PORTION statement, it removes the row:

  • When the row period falls completely within the delete period, it removes the row.
  • When the row period overlaps the delete period, it shrinks the row, removing the overlap from the first or second row period value.
  • When the delete period falls completely within the row period, it splits the row into two rows. The first row runs from the starting row period to the starting delete period. The second runs from the ending delete period to the ending row period.

To test this, first populate the table with some data to operate on:

CREATE TABLE t1(
   name VARCHAR(50), 
   date_1 DATE,
   date_2 DATE,
   PERIOD FOR date_period(date_1, date_2));

INSERT INTO t1 (name, date_1, date_2) VALUES
    ('a', '1999-01-01', '2000-01-01'),
    ('b', '1999-01-01', '2018-12-12'),
    ('c', '1999-01-01', '2017-01-01'),
    ('d', '2017-01-01', '2019-01-01');

SELECT * FROM t1;
+------+------------+------------+
| name | date_1     | date_2     |
+------+------------+------------+
| a    | 1999-01-01 | 2000-01-01 |
| b    | 1999-01-01 | 2018-12-12 |
| c    | 1999-01-01 | 2017-01-01 |
| d    | 2017-01-01 | 2019-01-01 |
+------+------------+------------+

Then, run the DELETE FOR PORTION statement:

DELETE FROM t1
FOR PORTION OF date_period
    FROM '2001-01-01' TO '2018-01-01';
Query OK, 3 rows affected (0.028 sec)

SELECT * FROM t1 ORDER BY name;
+------+------------+------------+
| name | date_1     | date_2     |
+------+------------+------------+
| a    | 1999-01-01 | 2000-01-01 |
| b    | 1999-01-01 | 2001-01-01 |
| b    | 2018-01-01 | 2018-12-12 |
| c    | 1999-01-01 | 2001-01-01 |
| d    | 2018-01-01 | 2019-01-01 |
+------+------------+------------+

Here:

  • a is unchanged, as the range falls entirely out of the specified portion to be deleted.
  • b, with values ranging from 1999 to 2018, is split into two rows, 1999 to 2000 and 2018-01 to 2018-12.
  • c, with values ranging from 1999 to 2017, where only the upper value falls within the portion to be deleted, has been shrunk to 1999 to 2001.
  • d, with values ranging from 2017 to 2019, where only the lower value falls within the portion to be deleted, has been shrunk to 2018 to 2019.

The DELETE FOR PORTION statement has the following restrictions

  • The FROM...TO clause must be constant
  • Multi-delete is not supported

If there are DELETE or INSERT triggers, it works as follows: any matched row is deleted, and then one or two rows are inserted. If the record is deleted completely, nothing is inserted.

Updating by Portion

The UPDATE syntax now supports UPDATE FOR PORTION, which modifies rows based on their occurrence in a range:

To test it, first populate the table with some data:

TRUNCATE t1;

INSERT INTO t1 (name, date_1, date_2) VALUES
    ('a', '1999-01-01', '2000-01-01'),
    ('b', '1999-01-01', '2018-12-12'),
    ('c', '1999-01-01', '2017-01-01'),
    ('d', '2017-01-01', '2019-01-01');

SELECT * FROM t1;
+------+------------+------------+
| name | date_1     | date_2     |
+------+------------+------------+
| a    | 1999-01-01 | 2000-01-01 |
| b    | 1999-01-01 | 2018-12-12 |
| c    | 1999-01-01 | 2017-01-01 |
| d    | 2017-01-01 | 2019-01-01 |
+------+------------+------------+

Then run the update:

UPDATE t1 FOR PORTION OF date_period
  FROM '2000-01-01' TO '2018-01-01' 
SET name = CONCAT(name,'_original');

SELECT * FROM t1 ORDER BY name;
+------------+------------+------------+
| name       | date_1     | date_2     |
+------------+------------+------------+
| a          | 1999-01-01 | 2000-01-01 |
| b          | 1999-01-01 | 2000-01-01 |
| b          | 2018-01-01 | 2018-12-12 |
| b_original | 2000-01-01 | 2018-01-01 |
| c          | 1999-01-01 | 2000-01-01 |
| c_original | 2000-01-01 | 2017-01-01 |
| d          | 2018-01-01 | 2019-01-01 |
| d_original | 2017-01-01 | 2018-01-01 |
+------------+------------+------------+
  • a is unchanged, as the range falls entirely out of the specified portion to be deleted.
  • b, with values ranging from 1999 to 2018, is split into two rows, 1999 to 2000 and 2018-01 to 2018-12.
  • c, with values ranging from 1999 to 2017, where only the upper value falls within the portion to be deleted, has been shrunk to 1999 to 2001.
  • d, with values ranging from 2017 to 2019, where only the lower value falls within the portion to be deleted, has been shrunk to 2018 to 2019.
  • Original rows affected by the update have "_original" appended to the name.

The UPDATE FOR PORTION statement has the following limitations:

  • The operation cannot modify the two temporal columns used by the time period
  • The operation cannot reference period values in the SET expression
  • FROM...TO expressions must be constant

WITHOUT OVERLAPS

MariaDB starting with 10.5.3

MariaDB 10.5 introduced a new clause, WITHOUT OVERLAPS, which allows one to create an index specifying that application time periods should not overlap.

An index constrained by WITHOUT OVERLAPS is required to be either a primary key or a unique index.

Take the following example, an application time period table for a booking system:

CREATE OR REPLACE TABLE rooms (
 room_number INT,
 guest_name VARCHAR(255),
 checkin DATE,
 checkout DATE,
 PERIOD FOR p(checkin,checkout)
 );

INSERT INTO rooms VALUES 
 (1, 'Regina', '2020-10-01', '2020-10-03'),
 (2, 'Cochise', '2020-10-02', '2020-10-05'),
 (1, 'Nowell', '2020-10-03', '2020-10-07'),
 (2, 'Eusebius', '2020-10-04', '2020-10-06');

Our system is not intended to permit overlapping bookings, so the fourth record above should not have been inserted. Using WITHOUT OVERLAPS in a unique index (in this case based on a combination of room number and the application time period) allows us to specify this constraint in the table definition.

CREATE OR REPLACE TABLE rooms (
 room_number INT,
 guest_name VARCHAR(255),
 checkin DATE,
 checkout DATE,
 PERIOD FOR p(checkin,checkout),
 UNIQUE (room_number, p WITHOUT OVERLAPS)
 );

INSERT INTO rooms VALUES 
 (1, 'Regina', '2020-10-01', '2020-10-03'),
 (2, 'Cochise', '2020-10-02', '2020-10-05'),
 (1, 'Nowell', '2020-10-03', '2020-10-07'),
 (2, 'Eusebius', '2020-10-04', '2020-10-06');
ERROR 1062 (23000): Duplicate entry '2-2020-10-06-2020-10-04' for key 'room_number'

Further Examples

The implicit change from NULL to NOT NULL:

CREATE TABLE `t2` (
  `id` int(11) DEFAULT NULL,
  `d1` datetime DEFAULT NULL,
  `d2` datetime DEFAULT NULL
) ENGINE=InnoDB DEFAULT CHARSET=latin1;

ALTER TABLE t2 ADD PERIOD FOR p(d1,d2);

SHOW CREATE TABLE t2\G
*************************** 1. row ***************************
       Table: t2
Create Table: CREATE TABLE `t2` (
  `id` int(11) DEFAULT NULL,
  `d1` datetime NOT NULL,
  `d2` datetime NOT NULL,
  PERIOD FOR `p` (`d1`, `d2`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1

Due to this constraint, trying to add a time period where null data already exists will fail.

CREATE OR REPLACE TABLE `t2` (
  `id` int(11) DEFAULT NULL,
  `d1` datetime DEFAULT NULL,
  `d2` datetime DEFAULT NULL
) ENGINE=InnoDB DEFAULT CHARSET=latin1;

INSERT INTO t2(id) VALUES(1);

ALTER TABLE t2 ADD PERIOD FOR p(d1,d2);
ERROR 1265 (01000): Data truncated for column 'd1' at row 1

See Also

1.1.7.3 Bitemporal Tables

MariaDB starting with 10.4.3

Bitemporal tables are tables that use versioning both at the system and application-time period levels.

Contents

  1. Using Bitemporal Tables
  2. See Also

Using Bitemporal Tables

To create a bitemporal table, use:

CREATE TABLE test.t3 (
   date_1 DATE,
   date_2 DATE,
   row_start TIMESTAMP(6) AS ROW START INVISIBLE,
   row_end TIMESTAMP(6) AS ROW END INVISIBLE,
   PERIOD FOR application_time(date_1, date_2),
   PERIOD FOR system_time(row_start, row_end))
WITH SYSTEM VERSIONING;

Note that, while system_time here is also a time period, it cannot be used in DELETE FOR PORTION or UPDATE FOR PORTION statements.

DELETE FROM test.t3 
FOR PORTION OF system_time 
    FROM '2000-01-01' TO '2018-01-01';
ERROR 42000: You have an error in your SQL syntax; check the manual that corresponds 
  to your MariaDB server version for the right syntax to use near
  'of system_time from '2000-01-01' to '2018-01-01'' at line 1

See Also

1.2 Built-in Functions

Functions and procedures in MariaDB

Secondary Functions

Special Functions

There are 7 related questions.

1.2.1 Function and Operator Reference

NameDescription
+Addition operator
/Division operator
*Multiplication operator
%Modulo operator. Returns the remainder of N divided by M
-Subtraction operator
!=Not equals
<Less than
<=Less than or equal
<=>NULL-safe equal
=Equal
>Greater than
>=Greater than or equal
&Bitwise AND
<<Shift left
>>Shift right
^Bitwise XOR
!Logical NOT
&&Logical AND
XORLogical XOR
||Logical OR
|Bitwise OR
:=Assignment operator
=Assignment and comparison operator
~Bitwise NOT
ABSReturns an absolute value
ACOSReturns an arc cosine
ADD_MONTHSAdd months to a date
ADDDATEAdd days or another interval to a date
ADDTIMEAdds a time to a time or datetime
AES_DECRYPTDecryption data encrypted with AES_ENCRYPT
AES_ENCRYPTEncrypts a string with the AES algorithm
AREASynonym for ST_AREA
AsBinarySynonym for ST_AsBinary
ASCIINumeric ASCII value of leftmost character
ASINReturns the arc sine
AsTextSynonym for ST_AsText
AsWKBSynonym for ST_AsBinary
AsWKTSynonym for ST_AsText
ATANReturns the arc tangent
ATAN2Returns the arc tangent of two variables
AVGReturns the average value
BENCHMARKExecutes an expression repeatedly
BETWEEN ANDTrue if expression between two values
BINReturns binary value
BINARY OPERATORCasts to a binary string
BINLOG_GTID_POSReturns a string representation of the corresponding GTID position
BIT_ANDBitwise AND
BIT_COUNTReturns the number of set bits
BIT_LENGTHReturns the length of a string in bits
BIT_ORBitwise OR
BIT_XORBitwise XOR
BOUNDARYSynonym for ST_BOUNDARY
BUFFERSynonym for ST_BUFFER
CASEReturns the result where value=compare_value or for the first condition that is true
CASTCasts a value of one type to another type
CEILSynonym for CEILING()
CEILINGReturns the smallest integer not less than X
CENTROIDSynonym for ST_CENTROID
CHAR FunctionReturns string based on the integer values for the individual characters
CHARACTER_LENGTHSynonym for CHAR_LENGTH()
CHAR_LENGTHLength of the string in characters
CHARSETReturns the character set
CHRReturns a string consisting of the character given by the code values of the integer
COALESCEReturns the first non-NULL parameter
COERCIBILITYReturns the collation coercibility value
COLLATIONCollation of the string argument
COLUMN_ADDAdds or updates dynamic columns
COLUMN_CHECKChecks if a dynamic column blob is valid
COLUMN_CREATEReturns a dynamic columns blob
COLUMN_DELETEDeletes a dynamic column
COLUMN_EXISTSChecks is a column exists
COLUMN_GETGets a dynamic column value by name
COLUMN_JSONReturns a JSON representation of dynamic column blob data
COLUMN_LISTReturns comma-separated list
COMPRESSReturns a binary, compressed string
CONCATReturns concatenated string
CONCAT_WSConcatenate with separator
CONNECTION_IDConnection thread ID
CONTAINSWhether one geometry contains another
CONVERTConvert a value from one type to another type
CONVConverts numbers between different number bases
CONVERT_TZConverts a datetime from on time zone to another
CONVEXHULLSynonym for ST_CONVEXHULL
COSReturns the cosine
COTReturns the cotangent
COUNTReturns count of non-null values
COUNT DISTINCTReturns count of number of different non-NULL values
CRC32Computes a cyclic redundancy check value
CROSSESWhether two geometries spatially cross
CUME_DISTWindow function that returns the cumulative distribution of a given row
CURDATEReturns the current date
CURRENT_DATESynonym for CURDATE()
CURRENT_ROLECurrent role name
CURRENT_TIMESynonym for CURTIME()
CURRENT_TIMESTAMPSynonym for NOW()
CURRENT_USERUsername/host that authenicated the current client
CURTIMEReturns the current time
DATABASECurrent default database
DATE FUNCTIONExtracts the date portion of a datetime
DATEDIFFDifference in days between two date/time values
DATE_ADDDate arithmetic - addition
DATE_FORMATFormats the date value according to the format string
DATE_SUBDate arithmetic - subtraction
DAYSynonym for DAYOFMONTH()
DAYNAMEReturn the name of the weekday
DAYOFMONTHReturns the day of the month
DAYOFWEEKReturns the day of the week index
DAYOFYEARReturns the day of the year
DECODEDecrypts a string encoded with ENCODE()
DECODE_HISTOGRAMReturns comma separated numerics corresponding to a probability distribution represented by a histogram
DEFAULTReturns column default
DEGREESConverts from radians to degrees
DENSE_RANKRank of a given row with identical values receiving the same result, no skipping
DES_DECRYPTDecrypts a string encrypted with DES_ENCRYPT()
DES_ENCRYPTEncrypts a string using the Triple-DES algorithm
DIMENSIONSynonym for ST_DIMENSION
DISJOINTWhether the two elements do not intersect
DIVInteger division
ELTReturns the N'th element from a set of strings
ENCODEEncrypts a string
ENCRYPTEncrypts a string with Unix crypt()
ENDPOINTSynonym for ST_ENDPOINT
ENVELOPESynonym for ST_ENVELOPE
EQUALSIndicates whether two geometries are spatially equal
EXPe raised to the power of the argument
EXPORT_SETReturns an on string for every bit set, an off string for every bit not set
ExteriorRingSynonym for ST_ExteriorRing
EXTRACTExtracts a portion of the date
EXTRACTVALUEReturns the text of the first text node matched by the XPath expression
FIELDReturns the index position of a string in a list
FIND_IN_SETReturns the position of a string in a set of strings
FLOORLargest integer value not greater than the argument
FORMATFormats a number
FOUND_ROWSNumber of (potentially) returned rows
FROM_BASE64Given a base-64 encoded string, returns the decoded result as a binary string
FROM_DAYSReturns a date given a day
FROM_UNIXTIMEReturns a datetime from a Unix timestamp
GeomCollFromTextSynonym for ST_GeomCollFromText
GeomCollFromWKBSynonym for ST_GeomCollFromWKB
GeometryCollectionFromTextSynonym for ST_GeomCollFromText
GeometryCollectionFromWKBSynonym for ST_GeomCollFromWKB
GeometryFromTextSynonym for ST_GeomFromText
GeometryFromWKBSynonym for ST_GeomFromWKB
GeomFromTextSynonym for ST_GeomFromText
GeomFromWKBSynonym for ST_GeomFromWKB
GeometryNSynonym for ST_GeometryN
GEOMETRYCOLLECTIONConstructs a WKB GeometryCollection
GeometryTypeSynonym for ST_GeometryType
GET_FORMATReturns a format string
GET_LOCKObtain LOCK
GLENGTHLength of a LineString value
GREATESTReturns the largest argument
GROUP_CONCATReturns string with concatenated values from a group
HEXReturns hexadecimal value
HOURReturns the hour
IFIf expr1 is TRUE, returns expr2; otherwise returns expr3
IFNULLCheck whether an expression is NULL
INTrue if expression equals any of the values in the list
INTERVALIndex of the argument that is less than the first argument
INET6_ATONGiven an IPv6 or IPv4 network address, returns a VARBINARY numeric value
INET6_NTOAGiven an IPv6 or IPv4 network address, returns the address as a nonbinary string
INET_ATONReturns numeric value of IPv4 address
INET_NTOAReturns dotted-quad representation of IPv4 address
INSERT FunctionReplaces a part of a string with another string
INSTRReturns the position of a string withing a string
InteriorRingNSynonym for ST_InteriorRingN
INTERSECTSIndicates whether two geometries spatially intersect
ISTests whether a boolean is TRUE, FALSE, or UNKNOWN
IsClosedSynonym for ST_IsClosed
IsEmptySynonym for ST_IsEmpty
IS_FREE_LOCKChecks whether lock is free to use
IS_IPV4Whether or not an expression is a valid IPv4 address
IS_IPV4_COMPATWhether or not an IPv6 address is IPv4-compatible
IS_IPV4_MAPPEDWhether an IPv6 address is a valid IPv4-mapped address
IS_IPV6Whether or not an expression is a valid IPv6 address
IS NOTTests whether a boolean value is not TRUE, FALSE, or UNKNOWN
IS NOT NULLTests whether a value is not NULL
IS NULLTests whether a value is NULL
ISNULLChecks if an expression is NULL
IsRingSynonym for ST_IsRing
IsSimpleSynonym for ST_IsSimple
IS_USED_LOCKCheck if lock is in use
JSON_ARRAYReturns a JSON array containing the listed values
JSON_ARRAY_APPENDAppends values to the end of the given arrays within a JSON document
JSON_ARRAY_INSERTInserts a value into a JSON document
JSON_COMPACTRemoves all unnecessary spaces so the json document is as short as possible
JSON_CONTAINSWhether a value is found in a given JSON document or at a specified path within the document
JSON_CONTAINS_PATHIndicates whether the given JSON document contains data at the specified path or paths
JSON_DEPTHMaximum depth of a JSON document
JSON_DETAILEDRepresents JSON in the most understandable way emphasizing nested structures
JSON_EQUALSCheck for equality between JSON objects.
JSON_EXISTSDetermines whether a specified JSON value exists in the given data
JSON_EXTRACTExtracts data from a JSON document.
JSON_INSERTInserts data into a JSON document
JSON_KEYSReturns keys from top-level value of a JSON object or top-level keys from the path
JSON_LENGTHReturns the length of a JSON document, or the length of a value within the document
JSON_LOOSEAdds spaces to a JSON document to make it look more readable
JSON_MERGEMerges the given JSON documents
JSON_MERGE_PATCHRFC 7396-compliant merge of the given JSON documents
JSON_MERGE_PRESERVESynonym for JSON_MERGE_PATCH.
JSON_NORMALIZERecursively sorts keys and removes spaces, allowing comparison of json documents for equality
JSON_OBJECTReturns a JSON object containing the given key/value pairs
JSON_OBJECTAGGReturns a JSON object containing key-value pairs
JSON_OVERLAPSCompares two json documents for overlaps
JSON_QUERYGiven a JSON document, returns an object or array specified by the path
JSON_QUOTEQuotes a string as a JSON value
JSON_REMOVERemoves data from a JSON document
JSON_REPLACEReplaces existing values in a JSON document
JSON_SEARCHReturns the path to the given string within a JSON document
JSON_SETUpdates or inserts data into a JSON document
JSON_TABLEReturns a representation of a JSON document as a relational table
JSON_TYPEReturns the type of a JSON value
JSON_UNQUOTEUnquotes a JSON value, returning a string
JSON_VALIDWhether a value is a valid JSON document or not
JSON_VALUEGiven a JSON document, returns the specified scalar
LAST_DAYReturns the last day of the month
LAST_INSERT_IDLast inserted autoinc value
LAST_VALUEReturns the last value in a list
LASTVALGet last value generated from a sequence
LCASESynonym for [LOWER()
LEASTReturns the smallest argument
LEFTReturns the leftmost characters from a string
LENGTHLength of the string in bytes
LIKEWhether expression matches a pattern
LineFromTextSynonym for ST_LineFromText
LineFromWKBSynonym for ST_LineFromWKB
LINESTRINGConstructs a WKB LineString value from a number of WKB Point arguments
LineStringFromTextSynonym for ST_LineFromText
LineStringFromWKBSynonym for ST_LineFromWKB
LNReturns natural logarithm
LOAD_FILEReturns file contents as a string
LOCALTIMESynonym for NOW()
LOCALTIMESTAMPSynonym for NOW()
LOCATEReturns the position of a substring in a string
LOGReturns the natural logarithm
LOG10Returns the base-10 logarithm
LOG2Returns the base-2 logarithm
LOWERReturns a string with all characters changed to lowercase
LPADReturns the string left-padded with another string to a given length
LTRIMReturns the string with leading space characters removed
MAKE_SETMake a set of strings that matches a bitmask
MAKEDATEReturns a date given a year and day
MAKETIMEReturns a time
MASTER_GTID_WAITWait until slave reaches the GTID position
MASTER_POS_WAITBlocks until the slave has applied all specified updates
MATCH AGAINSTPerform a fulltext search on a fulltext index
MAXReturns the maximum value
MBRContainsIndicates one Minimum Bounding Rectangle contains another
MBRDisjointIndicates whether the Minimum Bounding Rectangles of two geometries are disjoint
MBREqualWhether the Minimum Bounding Rectangles of two geometries are the same.
MBRIntersectsIndicates whether the Minimum Bounding Rectangles of the two geometries intersect
MBROverlapsWhether the Minimum Bounding Rectangles of two geometries overlap.
MBRTouchesWhether the Minimum Bounding Rectangles of two geometries touch.
MBRWithinIndicates whether one Minimum Bounding Rectangle is within another
MD5MD5 checksum
MEDIANWindow function that returns the median value of a range of values
MICROSECONDReturns microseconds from a date or datetime
MIDSynonym for SUBSTRING(str,pos,len)
MINReturns the minimum value
MINUTEReturns a minute from 0 to 59
MLineFromTextConstructs MULTILINESTRING using its WKT representation and SRID
MLineFromWKBConstructs a MULTILINESTRING
MODModulo operation. Remainder of N divided by M
MONTHReturns a month from 1 to 12
MONTHNAMEReturns the full name of the month
MPointFromTextConstructs a MULTIPOINT value using its WKT and SRID
MPointFromWKBConstructs a MULTIPOINT value using its WKB representation and SRID
MPolyFromTextConstructs a MULTIPOLYGON value
MPolyFromWKBConstructs a MULTIPOLYGON value using its WKB representation and SRID
MultiLineStringFromTextSynonym for MLineFromText
MultiLineStringFromWKBA synonym for MLineFromWKB
MULTIPOINTConstructs a WKB MultiPoint value
MultiPointFromTextSynonym for MPointFromText
MultiPointFromWKBSynonym for MPointFromWKB
MULTIPOLYGONConstructs a WKB MultiPolygon
MultiPolygonFromTextSynonym for MPolyFromText
MultiPolygonFromWKBSynonym for MPolyFromWKB
MULTILINESTRINGConstructs a MultiLineString value
NAME_CONSTReturns the given value
NATURAL_SORT_KEYSorting that is more more similar to natural human sorting
NOT LIKESame as NOT(expr LIKE pat [ESCAPE 'escape_char'])
NOT REGEXPSame as NOT (expr REGEXP pat)
NULLIFReturns NULL if expr1 = expr2
NEXTVALGenerate next value for sequence
NOT BETWEENSame as NOT (expr BETWEEN min AND max)
NOT INSame as NOT (expr IN (value,...))
NOWReturns the current date and time
NTILEReturns an integer indicating which group a given row falls into
NumGeometriesSynonym for ST_NumGeometries
NumInteriorRingsSynonym for NumInteriorRings
NumPointsSynonym for ST_NumPoints
OCTReturns octal value
OCTET_LENGTHSynonym for LENGTH()
OLD_PASSWORDPre MySQL 4.1 password implementation
ORDReturn ASCII or character code
OVERLAPSIndicates whether two elements spatially overlap
PASSWORDCalculates a password string
PERCENT_RANKWindow function that returns the relative percent rank of a given row
PERCENTILE_CONTReturns a value which corresponds to the given fraction in the sort order.
PERCENTILE_DISCReturns the first value in the set whose ordered position is the same or more than the specified fraction.
PERIOD_ADDAdd months to a period
PERIOD_DIFFNumber of months between two periods
PIReturns the value of π (pi)
POINTConstructs a WKB Point
PointFromTextSynonym for ST_PointFromText
PointFromWKBSynonym for PointFromWKB
PointNSynonym for PointN
PointOnSurfaceSynonym for ST_PointOnSurface
POLYGONConstructs a WKB Polygon value from a number of WKB LineString arguments
PolyFromTextSynonym for ST_PolyFromText
PolyFromWKBSynonym for ST_PolyFromWKB
PolygonFromTextSynonym for ST_PolyFromText
PolygonFromWKBSynonym for ST_PolyFromWKB
POSITIONReturns the position of a substring in a string
POWReturns X raised to the power of Y
POWERSynonym for POW()
QUARTERReturns year quarter from 1 to 4
QUOTEReturns quoted, properly escaped string
RADIANSConverts from degrees to radians
RANDRandom floating-point value
RANKRank of a given row with identical values receiving the same result
REGEXPPerforms pattern matching
REGEXP_INSTRPosition of the first appearance of a regex
REGEXP_REPLACEReplaces all occurrences of a pattern
REGEXP_SUBSTRReturns the matching part of a string
RELEASE_LOCKReleases lock obtained with GET_LOCK()
REPEAT FunctionReturns a string repeated a number of times
REPLACE FunctionReplace occurrences of a string
REVERSEReverses the order of a string
RIGHTReturns the rightmost N characters from a string
RLIKESynonym for REGEXP()
RPADReturns the string right-padded with another string to a given length
ROUNDRounds a number
ROW_COUNTNumber of rows affected by previous statement
ROW_NUMBERRow number of a given row with identical values receiving a different result
RTRIMReturns the string with trailing space characters removed
SCHEMASynonym for DATABASE()
SECONDReturns the second of a time
SEC_TO_TIMEConverts a second to a time
SETVALSet the next value to be returned by a sequence
SESSION_USERSynonym for USER()
SHASynonym for SHA1()
SHA1Calculates an SHA-1 checksum
SHA2Calculates an SHA-2 checksum
SIGNReturns 1, 0 or -1
SINReturns the sine
SLEEPPauses for the given number of seconds
SOUNDEXReturns a string based on how the string sounds
SOUNDS LIKESOUNDEX(expr1) = SOUNDEX(expr2)
SPACEReturns a string of space characters
SPIDER_BG_DIRECT_SQLBackground SQL execution
SPIDER_COPY_TABLESCopy table data
SPIDER_DIRECT_SQLExecute SQL on the remote server
SPIDER_FLUSH_TABLE_MON_CACHERefreshing Spider monitoring server information
SQRTSquare root
SRIDSynonym for ST_SRID
ST_AREAArea of a Polygon
ST_AsBinaryConverts a value to its WKB representation
ST_AsTextConverts a value to its WKT-Definition
ST_AsWKBSynonym for ST_AsBinary
ST_ASWKTSynonym for ST_ASTEXT()
ST_BOUNDARYReturns a geometry that is the closure of a combinatorial boundary
ST_BUFFERA new geometry with a buffer added to the original geometry
ST_CENTROIDThe mathematical centroid (geometric center) for a MultiPolygon
ST_CONTAINSWhether one geometry is contained by another
ST_CONVEXHULLThe minimum convex geometry enclosing all geometries within the set
ST_CROSSESWhether two geometries spatially cross
ST_DIFFERENCEPoint set difference
ST_DIMENSIONInherent dimension of a geometry value
ST_DISJOINTWhether one geometry is spatially disjoint from another
ST_DISTANCEThe distance between two geometries
ST_DISTANCE_SPHEREThe spherical distance between two geometries
ST_ENDPOINTReturns the endpoint of a LineString
ST_ENVELOPEReturns the Minimum Bounding Rectangle for a geometry value
ST_EQUALSWhether two geometries are spatoially equal
ST_ExteriorRingReturns the exterior ring of a Polygon as a LineString
ST_GeomCollFromTextConstructs a GEOMETRYCOLLECTION value
ST_GeomCollFromWKBConstructs a GEOMETRYCOLLECTION value from a WKB
ST_GeometryCollectionFromTextSynonym for ST_GeomCollFromText
ST_GeometryCollectionFromWKBSynonym for ST_GeomCollFromWKB
ST_GeometryFromTextSynonym for ST_GeomFromText
ST_GeometryFromWKBSynonym for ST_GeomFromWKB
ST_GEOMETRYNReturns the N-th geometry in a GeometryCollection
ST_GEOMETRYTYPEReturns name of the geometry type of which a given geometry instance is a member
ST_GeomFromTextConstructs a geometry value using its WKT and SRID
ST_GeomFromWKBConstructs a geometry value using its WKB representation and SRID
ST_InteriorRingNReturns the N-th interior ring for a Polygon
ST_INTERSECTIONThe intersection, or shared portion, of two geometries
ST_INTERSECTSWhether two geometries spatially intersect
ST_ISCLOSEDReturns true if a given LINESTRING's start and end points are the same
ST_ISEMPTYIndicated validity of geometry value
ST_IsRingReturns true if a given LINESTRING is both ST_IsClosed and ST_IsSimple
ST_IsSimpleReturns true if the given Geometry has no anomalous geometric points
ST_LENGTHLength of a LineString value
ST_LineFromTextCreates a linestring value
ST_LineFromWKBConstructs a LINESTRING using its WKB and SRID
ST_LineStringFromTextSynonym for ST_LineFromText
ST_LineStringFromWKBSynonym for ST_LineFromWKB
ST_NUMGEOMETRIESNumber of geometries in a GeometryCollection
ST_NumInteriorRingsNumber of interior rings in a Polygon
ST_NUMPOINTSReturns the number of Point objects in a LineString
ST_OVERLAPSWhether two geometries overlap
ST_PointFromTextConstructs a POINT value
ST_PointFromWKBConstructs POINT using its WKB and SRID
ST_POINTNReturns the N-th Point in the LineString
ST_POINTONSURFACEReturns a POINT guaranteed to intersect a surface
ST_PolyFromTextConstructs a POLYGON value
ST_PolyFromWKBConstructs POLYGON value using its WKB representation and SRID
ST_PolygonFromTextSynonym for ST_PolyFromText
ST_PolygonFromWKBSynonym for ST_PolyFromWKB
ST_RELATEReturns true if two geometries are related
ST_SRIDReturns a Spatial Reference System ID
ST_STARTPOINTReturns the start point of a LineString
ST_SYMDIFFERENCEPortions of two geometries that don't intersect
ST_TOUCHESWhether one geometry g1 spatially touches another
ST_UNIONUnion of two geometries
ST_WITHINWhether one geometry is within another
ST_XX-coordinate value for a point
ST_YY-coordinate for a point
STARTPOINTSynonym for ST_StartPoint
STDPopulation standard deviation
STDDEVPopulation standard deviation
STDDEV_POPReturns the population standard deviation
STDDEV_SAMPStandard deviation
STR_TO_DATEConverts a string to date
STRCMPCompares two strings in sort order
SUBDATESubtract a date unit or number of days
SUBSTRReturns a substring from string starting at a given position
SUBSTRINGReturns a substring from string starting at a given position
SUBSTRING_INDEXReturns the substring from string before count occurrences of a delimiter
SUBTIMESubtracts a time from a date/time
SUMSum total
SYS_GUIDGenerates a globally unique identifier
SYSDATEReturns the current date and time
SYSTEM_USERSynonym for USER()
TANReturns the tangent
TIME functionExtracts the time
TIMEDIFFReturns the difference between two date/times
TIMESTAMP FUNCTIONReturn the datetime, or add a time to a date/time
TIMESTAMPADDAdd interval to a date or datetime
TIMESTAMPDIFFDifference between two datetimes
TIME_FORMATFormats the time value according to the format string
TIME_TO_SECReturns the time argument, converted to seconds
TO_BASE64Converts a string to its base-64 encoded form
TO_CHARConverts a date/time type to a char
TO_DAYSNumber of days since year 0
TO_SECONDSNumber of seconds since year 0
TOUCHESWhether two geometries spatially touch
TRIMReturns a string with all given prefixes or suffixes removed
TRUNCATETruncates X to D decimal places
UCASESynonym for UPPER]]()
UNHEXInterprets pairs of hex digits as a number and converts to the character represented by the number
UNCOMPRESSUncompresses string compressed with COMPRESS()
UNCOMPRESSED_LENGTHReturns length of a string before being compressed with COMPRESS()
UNIX_TIMESTAMPReturns a Unix timestamp
UPDATEXMLReplace XML
UPPERChanges string to uppercase
USERCurrent user/host
UTC_DATEReturns the current UTC date
UTC_TIMEReturns the current UTC time
UTC_TIMESTAMPReturns the current UTC date and time
UUIDReturns a Universal Unique Identifier
UUID_SHORTReturn short universal identifier
VALUES or VALUERefer to columns in INSERT ... ON DUPLICATE KEY UPDATE
VAR_POPPopulation standard variance
VAR_SAMPReturns the sample variance
VARIANCEPopulation standard variance
VERSIONMariaDB server version
WEEKReturns the week number
WEEKDAYReturns the weekday index
WEEKOFYEARReturns the calendar week of the date as a number in the range from 1 to 53
WEIGHT_STRINGWeight of the input string
WITHINIndicate whether a geographic element is spacially within another
WSREP_LAST_SEEN_GTIDReturns the Global Transaction ID of the most recent write transaction observed by the client.
WSREP_LAST_WRITTEN_GTIDReturns the Global Transaction ID of the most recent write transaction performed by the client.
WSREP_SYNC_WAIT_UPTO_GTIDBlocks the client until the transaction specified by the given Global Transaction ID is applied and committed by the node
XSynonym for ST_X
YSynonym for ST_Y
YEARReturns the year for the given date
YEARWEEKReturns year and week for a date

1.2.2 String Functions

Functions dealing with strings, such as CHAR, CONVERT, CONCAT, PAD, REGEXP, TRIM, etc.

There are 3 related questions.

1.2.2.1 Regular Expressions Functions

MariaDB includes a number of functions for dealing with regular expressions.

There are 1 related questions.

1.2.2.1.1 Regular Expressions Overview

Contents

  1. Special Characters
    1. ^
    2. $
    3. .
    4. *
    5. +
    6. ?
    7. ()
    8. {}
    9. []
      1. ^
      2. Word boundaries
      3. Character Classes
      4. Character Names
    10. Combining
    11. Escaping

Regular Expressions allow MariaDB to perform complex pattern matching on a string. In many cases, the simple pattern matching provided by LIKE is sufficient. LIKE performs two kinds of matches:

  • _ - the underscore, matching a single character
  • % - the percentage sign, matching any number of characters.

In other cases you may need more control over the returned matches, and will need to use regular expressions.

MariaDB starting with 10.0.5

Until MariaDB 10.0.5, MariaDB used the POSIX 1003.2 compliant regular expression library. The new PCRE library is mostly backwards compatible with what is described below - see the PCRE Regular Expressions article for the enhancements made in 10.0.5.

Regular expression matches are performed with the REGEXP function. RLIKE is a synonym for REGEXP.

Comparisons are performed on the byte value, so characters that are treated as equivalent by a collation, but do not have the same byte-value, such as accented characters, could evaluate as unequal. Also note that until MariaDB 10.0.5, regular expressions were not multi-byte safe, and therefore could produce unexpected results in multi-byte character sets.

Without any special characters, a regular expression match is true if the characters match. The match is case-insensitive, except in the case of BINARY strings.

SELECT 'Maria' REGEXP 'Maria';
+------------------------+
| 'Maria' REGEXP 'Maria' |
+------------------------+
|                      1 |
+------------------------+

SELECT 'Maria' REGEXP 'maria';
+------------------------+
| 'Maria' REGEXP 'maria' |
+------------------------+
|                      1 |
+------------------------+

SELECT BINARY 'Maria' REGEXP 'maria';
+-------------------------------+
| BINARY 'Maria' REGEXP 'maria' |
+-------------------------------+
|                             0 |
+-------------------------------+

Note that the word being matched must match the whole pattern:

SELECT 'Maria' REGEXP 'Mari';
+-----------------------+
| 'Maria' REGEXP 'Mari' |
+-----------------------+
|                     1 |
+-----------------------+

SELECT 'Mari' REGEXP 'Maria';
+-----------------------+
| 'Mari' REGEXP 'Maria' |
+-----------------------+
|                     0 |
+-----------------------+

The first returns true because the pattern "Mari" exists in the expression "Maria". When the order is reversed, the result is false, as the pattern "Maria" does not exist in the expression "Mari"

A match can be performed against more than one word with the | character. For example:

SELECT 'Maria' REGEXP 'Monty|Maria';
+------------------------------+
| 'Maria' REGEXP 'Monty|Maria' |
+------------------------------+
|                            1 |
+------------------------------+

Special Characters

The above examples introduce the syntax, but are not very useful on their own. It's the special characters that give regular expressions their power.

^

^ matches the beginning of a string (inside square brackets it can also mean NOT - see below):

SELECT 'Maria' REGEXP '^Ma';
+----------------------+
| 'Maria' REGEXP '^Ma' |
+----------------------+
|                    1 |
+----------------------+

$

$ matches the end of a string:

SELECT 'Maria' REGEXP 'ia$';
+----------------------+
| 'Maria' REGEXP 'ia$' |
+----------------------+
|                    1 |
+----------------------+

.

. matches any single character:

SELECT 'Maria' REGEXP 'Ma.ia';
+------------------------+
| 'Maria' REGEXP 'Ma.ia' |
+------------------------+
|                      1 |
+------------------------+

SELECT 'Maria' REGEXP 'Ma..ia';
+-------------------------+
| 'Maria' REGEXP 'Ma..ia' |
+-------------------------+
|                       0 |
+-------------------------+

*

x* matches zero or more of a character x. In the examples below, it's the r character.

SELECT 'Maria' REGEXP 'Mar*ia';
+-------------------------+
| 'Maria' REGEXP 'Mar*ia' |
+-------------------------+
|                       1 |
+-------------------------+

SELECT 'Maia' REGEXP 'Mar*ia';
+------------------------+
| 'Maia' REGEXP 'Mar*ia' |
+------------------------+
|                      1 |
+------------------------+

SELECT 'Marrria' REGEXP 'Mar*ia';
+---------------------------+
| 'Marrria' REGEXP 'Mar*ia' |
+---------------------------+
|                         1 |
+---------------------------+

+

x+ matches one or more of a character x. In the examples below, it's the r character.

SELECT 'Maria' REGEXP 'Mar+ia';
+-------------------------+
| 'Maria' REGEXP 'Mar+ia' |
+-------------------------+
|                       1 |
+-------------------------+

SELECT 'Maia' REGEXP 'Mar+ia';
+------------------------+
| 'Maia' REGEXP 'Mar+ia' |
+------------------------+
|                      0 |
+------------------------+

SELECT 'Marrria' REGEXP 'Mar+ia';
+---------------------------+
| 'Marrria' REGEXP 'Mar+ia' |
+---------------------------+
|                         1 |
+---------------------------+

?

x? matches zero or one of a character x. In the examples below, it's the r character.

SELECT 'Maria' REGEXP 'Mar?ia';
+-------------------------+
| 'Maria' REGEXP 'Mar?ia' |
+-------------------------+
|                       1 |
+-------------------------+

SELECT 'Maia' REGEXP 'Mar?ia';
+------------------------+
| 'Maia' REGEXP 'Mar?ia' |
+------------------------+
|                      1 |
+------------------------+

SELECT 'Marrria' REGEXP 'Mar?ia';
+---------------------------+
| 'Marrria' REGEXP 'Mar?ia' |
+---------------------------+
|                         0 |
+---------------------------+

()

(xyz) - combine a sequence, for example (xyz)+ or (xyz)*

SELECT 'Maria' REGEXP '(ari)+';
+-------------------------+
| 'Maria' REGEXP '(ari)+' |
+-------------------------+
|                       1 |
+-------------------------+

{}

x{n} and x{m,n} This notation is used to match many instances of the x. In the case of x{n} the match must be exactly that many times. In the case of x{m,n}, the match can occur from m to n times. For example, to match zero or one instance of the string ari (which is identical to (ari)?), the following can be used:

SELECT 'Maria' REGEXP '(ari){0,1}';
+-----------------------------+
| 'Maria' REGEXP '(ari){0,1}' |
+-----------------------------+
|                           1 |
+-----------------------------+

[]

[xy] groups characters for matching purposes. For example, to match either the p or the r character:

SELECT 'Maria' REGEXP 'Ma[pr]ia';
+---------------------------+
| 'Maria' REGEXP 'Ma[pr]ia' |
+---------------------------+
|                         1 |
+---------------------------+

The square brackets also permit a range match, for example, to match any character from a-z, [a-z] is used. Numeric ranges are also permitted.

SELECT 'Maria' REGEXP 'Ma[a-z]ia';
+----------------------------+
| 'Maria' REGEXP 'Ma[a-z]ia' |
+----------------------------+
|                          1 |
+----------------------------+

The following does not match, as r falls outside of the range a-p.

SELECT 'Maria' REGEXP 'Ma[a-p]ia';
+----------------------------+
| 'Maria' REGEXP 'Ma[a-p]ia' |
+----------------------------+
|                          0 |
+----------------------------+
^

The ^ character means does NOT match, for example:

SELECT 'Maria' REGEXP 'Ma[^p]ia';
+---------------------------+
| 'Maria' REGEXP 'Ma[^p]ia' |
+---------------------------+
|                         1 |
+---------------------------+

SELECT 'Maria' REGEXP 'Ma[^r]ia';
+---------------------------+
| 'Maria' REGEXP 'Ma[^r]ia' |
+---------------------------+
|                         0 |
+---------------------------+

The [ and ] characters on their own can be literally matched inside a [] block, without escaping, as long as they immediately match the opening bracket:

SELECT '[Maria' REGEXP '[[]';
+-----------------------+
| '[Maria' REGEXP '[[]' |
+-----------------------+
|                     1 |
+-----------------------+

SELECT '[Maria' REGEXP '[]]';
+-----------------------+
| '[Maria' REGEXP '[]]' |
+-----------------------+
|                     0 |
+-----------------------+

SELECT ']Maria' REGEXP '[]]';
+-----------------------+
| ']Maria' REGEXP '[]]' |
+-----------------------+
|                     1 |
+-----------------------+

SELECT ']Maria' REGEXP '[]a]';
+------------------------+
| ']Maria' REGEXP '[]a]' |
+------------------------+
|                      1 |
+------------------------+

Incorrect order, so no match:

SELECT ']Maria' REGEXP '[a]]';
+------------------------+
| ']Maria' REGEXP '[a]]' |
+------------------------+
|                      0 |
+------------------------+

The - character can also be matched in the same way:

SELECT '-Maria' REGEXP '[1-10]';
+--------------------------+
| '-Maria' REGEXP '[1-10]' |
+--------------------------+
|                        0 |
+--------------------------+

SELECT '-Maria' REGEXP '[-1-10]';
+---------------------------+
| '-Maria' REGEXP '[-1-10]' |
+---------------------------+
|                         1 |
+---------------------------+

Word boundaries

The :<: and :>: patterns match the beginning and the end of a word respectively. For example:

SELECT 'How do I upgrade MariaDB?' REGEXP '[[:<:]]MariaDB[[:>:]]';
+------------------------------------------------------------+
| 'How do I upgrade MariaDB?' REGEXP '[[:<:]]MariaDB[[:>:]]' |
+------------------------------------------------------------+
|                                                          1 |
+------------------------------------------------------------+

SELECT 'How do I upgrade MariaDB?' REGEXP '[[:<:]]Maria[[:>:]]';
+----------------------------------------------------------+
| 'How do I upgrade MariaDB?' REGEXP '[[:<:]]Maria[[:>:]]' |
+----------------------------------------------------------+
|                                                        0 |
+----------------------------------------------------------+

Character Classes

There are a number of shortcuts to match particular preset character classes. These are matched with the [:character_class:] pattern (inside a [] set). The following character classes exist:

Character ClassDescription
alnumAlphanumeric
alphaAlphabetic
blankWhitespace
cntrlControl characters
digitDigits
graphGraphic characters
lowerLowercase alphabetic
printGraphic or space characters
punctPunctuation
spaceSpace, tab, newline, and carriage return
upperUppercase alphabetic
xdigitHexadecimal digit

For example:

SELECT 'Maria' REGEXP 'Mar[[:alnum:]]*';
+--------------------------------+
| 'Maria' REGEXP 'Mar[:alnum:]*' |
+--------------------------------+
|                              1 |
+--------------------------------+

Remember that matches are by default case-insensitive, unless a binary string is used, so the following example, specifically looking for an uppercase, counter-intuitively matches a lowercase character:

SELECT 'Mari' REGEXP 'Mar[[:upper:]]+';
+---------------------------------+
| 'Mari' REGEXP 'Mar[[:upper:]]+' |
+---------------------------------+
|                               1 |
+---------------------------------+

SELECT BINARY 'Mari' REGEXP 'Mar[[:upper:]]+';
+----------------------------------------+
| BINARY 'Mari' REGEXP 'Mar[[:upper:]]+' |
+----------------------------------------+
|                                      0 |
+----------------------------------------+

Character Names

There are also number of shortcuts to match particular preset character names. These are matched with the [.character.] pattern (inside a [] set). The following character classes exist:

NameCharacter
NUL0
SOH001
STX002
ETX003
EOT004
ENQ005
ACK006
BEL007
alert007
BS010
backspace'\b'
HT011
tab'\t'
LF012
newline'\n'
VT013
vertical-tab'\v'
FF014
form-feed'\f'
CR015
carriage-return'\r'
SO016
SI017
DLE020
DC1021
DC2022
DC3023
DC4024
NAK025
SYN026
ETB027
CAN030
EM031
SUB032
ESC033
IS4034
FS034
IS3035
GS035
IS2036
RS036
IS1037
US037
space' '
exclamation-mark'!'
quotation-mark'"'
number-sign'#'
dollar-sign'$'
percent-sign'%'
ampersand'&'
apostrophe'\''
left-parenthesis'('
right-parenthesis')'
asterisk'*'
plus-sign'+'
comma','
hyphen'-'
hyphen-minus'-'
period'.'
full-stop'.'
slash'/'
solidus'/'
zero'0'
one'1'
two'2'
three'3'
four'4'
five'5'
six'6'
seven'7'
eight'8'
nine'9'
colon':'
semicolon';'
less-than-sign'<'
equals-sign'='
greater-than-sign'>'
question-mark'?'
commercial-at'@'
left-square-bracket'['
backslash'
'
reverse-solidus'
'
right-square-bracket']'
circumflex'^'
circumflex-accent'^'
underscore'_'
low-line'_'
grave-accent'`'
left-brace'{'
left-curly-bracket'{'
vertical-line'|'
right-brace'}'
right-curly-bracket'}'
tilde''
DEL177

For example:

SELECT '|' REGEXP '[[.vertical-line.]]';
+----------------------------------+
| '|' REGEXP '[[.vertical-line.]]' |
+----------------------------------+
|                                1 |
+----------------------------------+

Combining

The true power of regular expressions is unleashed when the above is combined, to form more complex examples. Regular expression's reputation for complexity stems from the seeming complexity of multiple combined regular expressions, when in reality, it's simply a matter of understanding the characters and how they apply:

The first example fails to match, as while the Ma matches, either i or r only matches once before the ia characters at the end. 

SELECT 'Maria' REGEXP 'Ma[ir]{2}ia';
+------------------------------+
| 'Maria' REGEXP 'Ma[ir]{2}ia' |
+------------------------------+
|                            0 |
+------------------------------+

This example matches, as either i or r match exactly twice after the Ma, in this case one r and one i.

SELECT 'Maria' REGEXP 'Ma[ir]{2}';
+----------------------------+
| 'Maria' REGEXP 'Ma[ir]{2}' |
+----------------------------+
|                          1 |
+----------------------------+

Escaping

With the large number of special characters, care needs to be taken to properly escape characters. Two backslash characters,
(one for the MariaDB parser, one for the regex library), are required to properly escape a character. For example:

To match the literal (Ma:

SELECT '(Maria)' REGEXP '(Ma';
ERROR 1139 (42000): Got error 'parentheses not balanced' from regexp

SELECT '(Maria)' REGEXP '\(Ma';
ERROR 1139 (42000): Got error 'parentheses not balanced' from regexp

SELECT '(Maria)' REGEXP '\\(Ma';
+--------------------------+
| '(Maria)' REGEXP '\\(Ma' |
+--------------------------+
|                        1 |
+--------------------------+

To match r+: The first two examples are incorrect, as they match r one or more times, not r+:

SELECT 'Mar+ia' REGEXP 'r+';
+----------------------+
| 'Mar+ia' REGEXP 'r+' |
+----------------------+
|                    1 |
+----------------------+

SELECT 'Maria' REGEXP 'r+';
+---------------------+
| 'Maria' REGEXP 'r+' |
+---------------------+
|                   1 |
+---------------------+

SELECT 'Maria' REGEXP 'r\\+';
+-----------------------+
| 'Maria' REGEXP 'r\\+' |
+-----------------------+
|                     0 |
+-----------------------+

SELECT 'Maria' REGEXP 'r+';
+---------------------+
| 'Maria' REGEXP 'r+' |
+---------------------+
|                   1 |
+---------------------+

1.2.2.1.2 Perl Compatible Regular Expressions (PCRE) Documentation

Contents

  1. PCRE Versions
  2. PCRE Enhancements
  3. New Regular Expression Functions
  4. PCRE Syntax
    1. Special Characters
    2. Character Classes
    3. Generic Character Types
    4. Unicode Character Properties
      1. General Category Properties For \p and \P
      2. Special Category Properties For \p and \P
      3. Script Names For \p and \P
    5. Extended Unicode Grapheme Sequence
    6. Simple Assertions
    7. Option Setting
    8. Multiline Matching
    9. Newline Conventions
    10. Newline Sequences
    11. Comments
    12. Quoting
    13. Resetting the Match Start
    14. Non-Capturing Groups
    15. Non-Greedy Quantifiers
    16. Atomic Groups
    17. Possessive quantifiers
    18. Absolute and Relative Numeric Backreferences
    19. Named Subpatterns and Backreferences
    20. Positive and Negative Look-Ahead and Look-Behind Assertions
    21. Subroutine Reference and Recursive Patterns
    22. Defining Subpatterns For Use By Reference
    23. Conditional Subpatterns
      1. Conditions With Subpattern References
      2. Other Kinds of Conditions
    24. Matching Zero Bytes (0x00)
    25. Other PCRE Features
    26. default_regex_flags Examples
    27. See Also

PCRE Versions

PCRE VersionIntroducedMaturity
PCRE2 10.34MariaDB 10.5.1Stable
PCRE 8.43MariaDB 10.1.39Stable
PCRE 8.42MariaDB 10.2.15, MariaDB 10.1.33, MariaDB 10.0.35Stable
PCRE 8.41MariaDB 10.2.8, MariaDB 10.1.26, MariaDB 10.0.32Stable
PCRE 8.40MariaDB 10.2.5, MariaDB 10.1.22, MariaDB 10.0.30Stable
PCRE 8.39MariaDB 10.1.15, MariaDB 10.0.26Stable
PCRE 8.38MariaDB 10.1.10, MariaDB 10.0.23Stable
PCRE 8.37MariaDB 10.1.5, MariaDB 10.0.18Stable
PCRE 8.36MariaDB 10.1.2, MariaDB 10.0.15Stable
PCRE 8.35MariaDB 10.1.0, MariaDB 10.0.12Stable
PCRE 8.34MariaDB 10.0.8Stable

PCRE Enhancements

MariaDB 10.0.5 switched to the PCRE library, which significantly improved the power of the REGEXP/RLIKE operator.

The switch to PCRE added a number of features, including recursive patterns, named capture, look-ahead and look-behind assertions, non-capturing groups, non-greedy quantifiers, Unicode character properties, extended syntax for characters and character classes, multi-line matching, and many other.

Additionally, MariaDB 10.0.5 introduced three new functions that work with regular expressions: REGEXP_REPLACE(), REGEXP_INSTR() and REGEXP_SUBSTR().

Also, REGEXP/RLIKE, and the new functions, now work correctly with all multi-byte character sets supported by MariaDB, including East-Asian character sets (big5, gb2313, gbk, eucjp, eucjpms, cp932, ujis, euckr), and Unicode character sets (utf8, utf8mb4, ucs2, utf16, utf16le, utf32). In earlier versions of MariaDB (and all MySQL versions) REGEXP/RLIKE works correctly only with 8-bit character sets.

New Regular Expression Functions

See the individual articles for more details and examples.

PCRE Syntax

In most cases PCRE is backward compatible with the old POSIX 1003.2 compliant regexp library (see Regular Expressions Overview), so you won't need to change your applications that use SQL queries with the REGEXP/RLIKE predicate.

MariaDB 10.0.11 introduced the default_regex_flags variable to address the remaining compatibilities between PCRE and the old regex library.

This section briefly describes the most important extended PCRE features. For more details please refer to the documentation on the PCRE site, or to the documentation which is bundled in the /pcre/doc/html/ directory of a MariaDB sources distribution. The pages pcresyntax.html and pcrepattern.html should be a good start. Regular-Expressions.Info is another good resource to learn about PCRE and regular expressions generally.

Special Characters

PCRE supports the following escape sequences to match special characters:

SequenceDescription
\a0x07 (BEL)
\cx"control-x", where x is any ASCII character
\e0x1B (escape)
\f0x0C (form feed)
\n0x0A (newline)
\r0x0D (carriage return)
\t0x09 (TAB)
\dddcharacter with octal code ddd
\xhhcharacter with hex code hh
\x{hhh..}character with hex code hhh..

Note, the backslash characters (here, and in all examples in the sections below) must be escaped with another backslash, unless you're using the SQL_MODE NO_BACKSLASH_ESCAPES.

This example tests if a character has hex code 0x61:

SELECT 'a' RLIKE '\\x{61}';
-> 1

Character Classes

PCRE supports the standard POSIX character classes such as alnum, alpha, blank, cntrl, digit, graph, lower, print, punct, space, upper, xdigit, with the following additional classes:

ClassDescription
asciiany ASCII character (0x00..0x7F)
wordany "word" character (a letter, a digit, or an underscore)

This example checks if the string consists of ASCII characters only:

SELECT 'abc' RLIKE '^[[:ascii:]]+$';
-> 1

Generic Character Types

Generic character types complement the POSIX character classes and serve to simplify writing patterns:

ClassDescription
\da decimal digit (same as [:digit:])
\Da character that is not a decimal digit
\ha horizontal white space character
\Ha character that is not a horizontal white space character
\Na character that is not a new line
\Ra newline sequence
\sa white space character
\Sa character that is not a white space character
\va vertical white space character
\Va character that is not a vertical white space character
\wa "word" character (same as [:word:])
\Wa "non-word" character

This example checks if the string consists of "word" characters only:

SELECT 'abc' RLIKE '^\\w+$';
-> 1

Unicode Character Properties

\p{xx} is a character with the xx property, and \P{xx} is a character without the xx property.

The property names represented by xx above are limited to the Unicode script names, the general category properties, and "Any", which matches any character (including newline). Those that are not part of an identified script are lumped together as "Common".

General Category Properties For \p and \P

PropertyDescription
COther
CcControl
CfFormat
CnUnassigned
CoPrivate use
CsSurrogate
LLetter
LlLower case letter
LmModifier letter
LoOther letter
LtTitle case letter
LuUpper case letter
L&Ll, Lu, or Lt
MMark
McSpacing mark
MeEnclosing mark
MnNon-spacing mark
NNumber
NdDecimal number
NlLetter number
NoOther number
PPunctuation
PcConnector punctuation
PdDash punctuation
PeClose punctuation
PfFinal punctuation
PiInitial punctuation
PoOther punctuation
PsOpen punctuation
SSymbol
ScCurrency symbol
SkModifier symbol
SmMathematical symbol
SoOther symbol
ZSeparator
ZlLine separator
ZpParagraph separator
ZsSpace separator

This example checks if the string consists only of characters with property N (number):

SELECT '1¼①' RLIKE '^\\p{N}+$';
-> 1

Special Category Properties For \p and \P

PropertyDescription
XanAlphanumeric: union of properties L and N
XpsPOSIX space: property Z or tab, NL, VT, FF, CR
XspPerl space: property Z or tab, NL, FF, CR
XucA character than can be represented by a Universal Character Name
XwdPerl word: property Xan or underscore

The property Xuc matches any character that can be represented by a Universal Character Name (in C++ and other programming languages). These include $, @, `, and all characters with Unicode code points greater than U+00A0, excluding the surrogates U+D800..U+DFFF.

Script Names For \p and \P

Arabic, Armenian, Avestan, Balinese, Bamum, Batak, Bengali, Bopomofo, Brahmi, Braille, Buginese, Buhid, Canadian_Aboriginal, Carian, Chakma, Cham, Cherokee, Common, Coptic, Cuneiform, Cypriot, Cyrillic, Deseret, Devanagari, Egyptian_Hieroglyphs, Ethiopic, Georgian, Glagolitic, Gothic, Greek, Gujarati, Gurmukhi, Han, Hangul, Hanunoo, Hebrew, Hiragana, Imperial_Aramaic, Inherited, Inscriptional_Pahlavi, Inscriptional_Parthian, Javanese, Kaithi, Kannada, Katakana, Kayah_Li, Kharoshthi, Khmer, Lao, Latin, Lepcha, Limbu, Linear_B, Lisu, Lycian, Lydian, Malayalam, Mandaic, Meetei_Mayek, Meroitic_Cursive, Meroitic_Hieroglyphs, Miao, Mongolian, Myanmar, New_Tai_Lue, Nko, Ogham, Old_Italic, Old_Persian, Old_South_Arabian, Old_Turkic, Ol_Chiki, Oriya, Osmanya, Phags_Pa, Phoenician, Rejang, Runic, Samaritan, Saurashtra, Sharada, Shavian, Sinhala, Sora_Sompeng, Sundanese, Syloti_Nagri, Syriac, Tagalog, Tagbanwa, Tai_Le, Tai_Tham, Tai_Viet, Takri, Tamil, Telugu, Thaana, Thai, Tibetan, Tifinagh, Ugaritic, Vai, Yi.

This example checks if the string consists only of Greek characters:

SELECT 'ΣΦΩ' RLIKE '^\\p{Greek}+$';
-> 1

Extended Unicode Grapheme Sequence

The \X escape sequence matches a character sequence that makes an "extended grapheme cluster", i.e. a composite character that consists of multiple Unicode code points.

One of the examples of a composite character can be a letter followed by non-spacing accent marks. This example demonstrates that U+0045 LATIN CAPITAL LETTER E followed by U+0302 COMBINING CIRCUMFLEX ACCENT followed by U+0323 COMBINING DOT BELOW together form an extended grapheme cluster:

SELECT _ucs2 0x004503020323 RLIKE '^\\X$';
-> 1

See the PCRE documentation for the other types of extended grapheme clusters.

Simple Assertions

An assertion specifies a certain condition that must match at a particular point, but without consuming characters from the subject string. In addition to the standard POSIX simple assertions ^ (that matches at the beginning of a line) and $ (that matches at the end of a line), PCRE supports a number of other assertions:

AssertionDescription
\bmatches at a word boundary
\Bmatches when not at a word boundary
\Amatches at the start of the subject
\Zmatches at the end of the subject, also matches before a newline at the end of the subject
\zmatches only at the end of the subject
\Gmatches at the first matching position in the subject

This example cuts a word that consists only of 3 characters from a string:

SELECT REGEXP_SUBSTR('---abcd---xyz---', '\\b\\w{3}\\b');
-> xyz

Notice that the two \b assertions checked the word boundaries but did not get into the matching pattern.

The \b assertions work well in the beginning and the end of the subject string:

SELECT REGEXP_SUBSTR('xyz', '\\b\\w{3}\\b');
-> xyz

By default, the ^ and $ assertions have the same meaning with \A, \Z, and \z. However, the meanings of ^ and $ can change in multiline mode (see below). By contrast, the meanings of \A, \Z, and \z are always the same; they are independent of the multiline mode.

Option Setting

A number of options that control the default match behavior can be changed within the pattern by a sequence of option letters enclosed between (? and ).

OptionDescription
(?i)case insensitive match
(?m)multiline mode
(?s)dotall mode (dot matches newline characters)
(?x)extended (ignore white space)
(?U)ungreedy (lazy) match
(?J)allow named subpatterns with duplicate names
(?X)extra PCRE functionality (e.g. force error on unknown escaped character)
(?-...)unset option(s)

For example, (?im) sets case insensitive multiline matching.

A hyphen followed by the option letters unset the options. For example, (?-im) means case sensitive single line match.

A combined setting and unsetting is also possible, e.g. (?im-sx).

If an option is set outside of subpattern parentheses, the option applies to the remainder of the pattern that follows the option. If an option is set inside a subpattern, it applies to the part of this subpattern that follows the option.

In this example the pattern (?i)m((?-i)aria)db matches the words MariaDB, Mariadb, mariadb, but not MARIADB:

SELECT 'MariaDB' RLIKE '(?i)m((?-i)aria)db';
-> 1

SELECT 'mariaDB' RLIKE '(?i)m((?-i)aria)db';
-> 1

SELECT 'Mariadb' RLIKE '(?i)m((?-i)aria)db';
-> 1

SELECT 'MARIADB' RLIKE '(?i)m((?-i)aria)db';
-> 0

This example demonstrates that the (?x) option makes the regexp engine ignore all white spaces in the pattern (other than in a class).

SELECT 'ab' RLIKE '(?x)a b';
-> 1

Note, putting spaces into a pattern in combination with the (?x) option can be useful to split different logical parts of a complex pattern, to make it more readable.

Multiline Matching

Multiline matching changes the meaning of ^ and $ from "the beginning of the subject string" and "the end of the subject string" to "the beginning of any line in the subject string" and "the end of any line in the subject string" respectively.

This example checks if the subject string contains two consequent lines that fully consist of digits:

SELECT 'abc\n123\n456\nxyz\n' RLIKE '(?m)^\\d+\\R\\d+$';
-> 1

Notice the (?m) option in the beginning of the pattern, which switches to the multiline matching mode.

Newline Conventions

PCRE supports five line break conventions:

  • CR (\r) - a single carriage return character
  • LF (\n) - a single linefeed character
  • CRLF (\r\n) - a carriage return followed by a linefeed
  • any of the previous three
  • any Unicode newline sequence

By default, the newline convention is set to any Unicode newline sequence, which includes:

SequenceDescription
LF(U+000A, carriage return)
CR(U+000D, carriage return)
CRLF(a carriage return followed by a linefeed)
VT(U+000B, vertical tab)
FF(U+000C, form feed)
NEL(U+0085, next line)
LS(U+2028, line separator)
PS(U+2029, paragraph separator)

The newline convention can be set by starting a pattern with one of the following sequences:

SequenceDescription
(*CR)carriage return
(*LF)linefeed
(*CRLF)carriage return followed by linefeed
(*ANYCRLF)any of the previous three
(*ANY)all Unicode newline sequences

The newline conversion affects the ^ and $ assertions, the interpretation of the dot metacharacter, and the behavior of \N.

Note, the new line convention does not affect the meaning of \R.

This example demonstrates that the dot metacharacter matches \n, because it is not a newline sequence anymore:

SELECT 'a\nb' RLIKE '(*CR)a.b';
-> 1

Newline Sequences

By default, the escape sequence \R matches any Unicode newline sequences.

The meaning of \R can be set by starting a pattern with one of the following sequences:

SequenceDescription
(*BSR_ANYCRLF)any of CR, LF or CRLF
(*BSR_UNICODE)any Unicode newline sequence

Comments

It's possible to include comments inside a pattern. Comments do not participate in the pattern matching. Comments start at the (?# sequence and continue up to the next closing parenthesis:

SELECT 'ab12' RLIKE 'ab(?#expect digits)12';
-> 1

Quoting

POSIX uses the backslash to remove a special meaning from a character. PCRE introduces a syntax to remove special meaning from a sequence of characters. The characters inside \Q ... \E are treated literally, without their special meaning.

This example checks if the string matches a dollar sign followed by a parenthesized name (a variable reference in some languages):

SELECT '$(abc)' RLIKE '^\\Q$(\\E\\w+\\Q)\\E$';
-> 1

Note that the leftmost dollar sign and the parentheses are used literally, while the rightmost dollar sign is still used to match the end of the string.

Resetting the Match Start

The escape sequence \K causes any previously matched characters to be excluded from the final matched sequence. For example, the pattern: (foo)\Kbar matches foobar, but reports that it has matched bar. This feature is similar to a look-behind assertion. However, in this case, the part of the subject before the real match does not have to be of fixed length:

SELECT REGEXP_SUBSTR('aaa123', '[a-z]*\\K[0-9]*');
-> 123

Non-Capturing Groups

The question mark and the colon after the opening parenthesis create a non-capturing group: (?:...).

This example removes an optional article from a word, for example for better sorting of the results.

SELECT REGEXP_REPLACE('The King','(?:the|an|a)[^a-z]([a-z]+)','\\1');
-> King

Note that the articles are listed inside the left parentheses using the alternation operator | but they do not produce a captured subpattern, so the word followed by the article is referenced by '
1' in the third argument to the function. Using non-capturing groups can be useful to save numbers on the sup-patterns that won't be used in the third argument of REGEXP_REPLACE(), as well as for performance purposes.

Non-Greedy Quantifiers

By default, the repetition quantifiers ?, *, + and {n,m} are "greedy", that is, they try to match as much as possible. Adding a question mark after a repetition quantifier makes it "non-greedy", so the pattern matches the minimum number of times possible.

This example cuts C comments from a line:

SELECT REGEXP_REPLACE('/* Comment1 */ i+= 1; /* Comment2 */', '/[*].*?[*]/','');
->  i+= 1;

The pattern without the non-greedy flag to the quantifier /[*].*[*]/ would match the entire string between the leftmost /* and the rightmost */.

Atomic Groups

A sequence inside (?>...) makes an atomic group. Backtracking inside an atomic group is prevented once it has matched; however, backtracking past to the previous items works normally.

Consider the pattern \d+foo applied to the subject string 123bar. Once the engine scans 123 and fails on the letter b, it would normally backtrack to 2 and try to match again, then fail and backtrack to 1 and try to match and fail again, and finally fail the entire pattern. In case of an atomic group (?>\d+)foo with the same subject string 123bar, the engine gives up immediately after the first failure to match foo. An atomic group with a quantifier can match all or nothing.

Atomic groups produce faster false results (i.e. in case when a long subject string does not match the pattern), because the regexp engine saves performance on backtracking. However, don't hurry to put everything into atomic groups. This example demonstrates the difference between atomic and non-atomic match:

SELECT 'abcc' RLIKE 'a(?>bc|b)c' AS atomic1;
-> 1

SELECT 'abc' RLIKE 'a(?>bc|b)c' AS atomic2;
-> 0
 
SELECT 'abcc' RLIKE 'a(bc|b)c' AS non_atomic1;
-> 1

SELECT 'abc' RLIKE 'a(bc|b)c' AS non_atomic2;
-> 1

The non-atomic pattern matches both abbc and abc, while the atomic pattern matches abbc only.

The atomic group (?>bc|b) in the above example can be "translated" as "if there is bc, then don't try to match as b". So b can match only if bc is not found.

Atomic groups are not capturing. To make an atomic group capturing, put it into parentheses:

SELECT REGEXP_REPLACE('abcc','a((?>bc|b))c','\\1');
-> bc

Possessive quantifiers

An atomic group which ends with a quantifier can be rewritten using a so called "possessive quantifier" syntax by putting an additional + sign following the quantifier.

The pattern (?>\d+)foo from the previous section's example can be rewritten as \d++foo.

Absolute and Relative Numeric Backreferences

Backreferences match the same text as previously matched by a capturing group. Backreferences can be written using:

  • a backslash followed by a digit
  • the \g escape sequence followed by a positive or negative number
  • the \g escape sequence followed by a positive or negative number enclosed in braces

The following backreferences are identical and refer to the first capturing group:

  • \1
  • \g1
  • \g{1}

This example demonstrates a pattern that matches "sense and sensibility" and "response and responsibility", but not "sense and responsibility":

SELECT 'sense and sensibility' RLIKE '(sens|respons)e and \\1ibility';
-> 1

This example removes doubled words that can unintentionally creep in when you edit a text in a text editor:

SELECT REGEXP_REPLACE('using using the the regexp regexp',
 '\\b(\\w+)\\s+\\1\\b','\\1');
-> using the regexp

Note that all double words were removed, in the beginning, in the middle and in the end of the subject string.

A negative number in a \g sequence means a relative reference. Relative references can be helpful in long patterns, and also in patterns that are created by joining fragments together that contain references within themselves. The sequence \g{-1} is a reference to the most recently started capturing subpattern before \g.

In this example \g{-1} is equivalent to \2:

SELECT 'abc123def123' RLIKE '(abc(123)def)\\g{-1}';     
-> 1

SELECT 'abc123def123' RLIKE '(abc(123)def)\\2';
-> 1

Named Subpatterns and Backreferences

Using numeric backreferences for capturing groups can be hard to track in a complicated regular expression. Also, the numbers can change if an expression is modified. To overcome these difficulties, PCRE supports named subpatterns.

A subpattern can be named in one of three ways: (?<name>...) or (?'name'...) as in Perl, or (?P<name>...) as in Python. References to capturing subpatterns from other parts of the pattern, can be made by name as well as by number.

Backreferences to a named subpattern can be written using the .NET syntax \k{name}, the Perl syntax \k<name> or \k'name' or \g{name}, or the Python syntax (?P=name).

This example tests if the string is a correct HTML tag:

SELECT '<a href="../">Up</a>' RLIKE '<(?<tag>[a-z][a-z0-9]*)[^>]*>[^<]*</(?P=tag)>';
-> 1

Positive and Negative Look-Ahead and Look-Behind Assertions

Look-ahead and look-behind assertions serve to specify the context for the searched regular expression pattern. Note that the assertions only check the context, they do not capture anything themselves!

This example finds the letter which is not followed by another letter (negative look-ahead):

SELECT REGEXP_SUBSTR('ab1','[a-z](?![a-z])');
-> b

This example finds the letter which is followed by a digit (positive look-ahead):

SELECT REGEXP_SUBSTR('ab1','[a-z](?=[0-9])');
-> b

This example finds the letter which does not follow a digit character (negative look-behind):

SELECT REGEXP_SUBSTR('1ab','(?<![0-9])[a-z]');
-> b

This example finds the letter which follows another letter character (positive look-behind):

SELECT REGEXP_SUBSTR('1ab','(?<=[a-z])[a-z]');
-> b

Note that look-behind assertions can only be of fixed length; you cannot have repetition operators or alternations with different lengths:

SELECT 'aaa' RLIKE '(?<=(a|bc))a';
ERROR 1139 (42000): Got error 'lookbehind assertion is not fixed length at offset 10' from regexp

Subroutine Reference and Recursive Patterns

PCRE supports a special syntax to recourse the entire pattern or its individual subpatterns:

SyntaxDescription
(?R)Recourse the entire pattern
(?n)call subpattern by absolute number
(?+n)call subpattern by relative number
(?-n)call subpattern by relative number
(?&name)call subpattern by name (Perl)
(?P>name)call subpattern by name (Python)
\g<name>call subpattern by name (Oniguruma)
\g'name'call subpattern by name (Oniguruma)
\g<n>call subpattern by absolute number (Oniguruma)
\g'n'call subpattern by absolute number (Oniguruma)
\g<+n>call subpattern by relative number
\g<-n>call subpattern by relative number
\g'+n'call subpattern by relative number
\g'-n'call subpattern by relative number

This example checks for a correct additive arithmetic expression consisting of numbers, unary plus and minus, binary plus and minus, and parentheses:

SELECT '1+2-3+(+(4-1)+(-2)+(+1))' RLIKE  '^(([+-]?(\\d+|[(](?1)[)]))(([+-](?1))*))$';
-> 1

The recursion is done using (?1) to call for the first parenthesized subpattern, which includes everything except the leading ^ and the trailing $.

The regular expression in the above example implements the following BNF grammar:

  1. <expression> ::= <term> [(<sign> <term>)...]
  2. <term> ::= [ <sign> ] <primary>
  3. <primary> ::= <number> | <left paren> <expression> <right paren>
  4. <sign> ::= <plus sign> | <minus sign>

Defining Subpatterns For Use By Reference

Use the (?(DEFINE)...) syntax to define subpatterns that can be referenced from elsewhere.

This example defines a subpattern with the name letters that matches one or more letters, which is further reused two times:

SELECT 'abc123xyz' RLIKE '^(?(DEFINE)(?<letters>[a-z]+))(?&letters)[0-9]+(?&letters)$';
-> 1

The above example can also be rewritten to define the digit part as a subpattern as well:

SELECT 'abc123xyz' RLIKE
 '^(?(DEFINE)(?<letters>[a-z]+)(?<digits>[0-9]+))(?&letters)(?&digits)(?&letters)$';
-> 1

Conditional Subpatterns

There are two forms of conditional subpatterns:

(?(condition)yes-pattern)
(?(condition)yes-pattern|no-pattern)

The yes-pattern is used if the condition is satisfied, otherwise the no-pattern (if any) is used.

Conditions With Subpattern References

If a condition consists of a number, it makes a condition with a subpattern reference. Such a condition is true if a capturing subpattern corresponding to the number has previously matched.

This example finds an optionally parenthesized number in a string:

SELECT REGEXP_SUBSTR('a(123)b', '([(])?[0-9]+(?(1)[)])');
-> (123)

The ([(])? part makes a capturing subpattern that matches an optional opening parenthesis; the [0-9]+ part matches a number, and the (?(1)[)]) part matches a closing parenthesis, but only if the opening parenthesis has been previously found.

Other Kinds of Conditions

The other possible condition kinds are: recursion references and assertions. See the PCRE documentation for details.

Matching Zero Bytes (0x00)

PCRE correctly works with zero bytes in the subject strings:

SELECT 'a\0b' RLIKE '^a.b$';
-> 1

Zero bytes, however, are not supported literally in the pattern strings and should be escaped using the \xhh or \x{hh} syntax:

SELECT 'a\0b' RLIKE '^a\\x{00}b$';
-> 1

Other PCRE Features

PCRE provides other extended features that were not covered in this document, such as duplicate subpattern numbers, backtracking control, breaking utf-8 sequences into individual bytes, setting the match limit, setting the recursion limit, optimization control, recursion conditions, assertion conditions and more types of extended grapheme clusters. Please refer to the PCRE documentation for details.

Enhanced regex was implemented as a GSoC 2013 project by Sudheera Palihakkara.

default_regex_flags Examples

MariaDB starting with 10.0.11

The default_regex_flags variable was introduced in MariaDB 10.0.11

The default_regex_flags variable was introduced to address the remaining incompatibilities between PCRE and the old regex library. Here are some examples of its usage:

The default behaviour (multiline match is off)

SELECT 'a\nb\nc' RLIKE '^b$';
+---------------------------+
| '(?m)a\nb\nc' RLIKE '^b$' |
+---------------------------+
|                         0 |
+---------------------------+

Enabling the multiline option using the PCRE option syntax:

SELECT 'a\nb\nc' RLIKE '(?m)^b$';
+---------------------------+
| 'a\nb\nc' RLIKE '(?m)^b$' |
+---------------------------+
|                         1 |
+---------------------------+

Enabling the miltiline option using default_regex_flags

SET default_regex_flags='MULTILINE';
SELECT 'a\nb\nc' RLIKE '^b$';
+-----------------------+
| 'a\nb\nc' RLIKE '^b$' |
+-----------------------+
|                     1 |
+-----------------------+

See Also

1.2.2.1.3 NOT REGEXP

Syntax

expr NOT REGEXP pat, expr NOT RLIKE pat

Description

This is the same as NOT (expr REGEXP pat).

1.2.2.1.4 REGEXP

Syntax

expr REGEXP pat, expr RLIKE pat

Description

Performs a pattern match of a string expression expr against a pattern pat. The pattern can be an extended regular expression. See Regular Expressions Overview for details on the syntax for regular expressions (see also PCRE Regular Expressions).

Returns 1 if expr matches pat or 0 if it doesn't match. If either expr or pat are NULL, the result is NULL.

The negative form NOT REGEXP also exists, as an alias for NOT (string REGEXP pattern). RLIKE and NOT RLIKE are synonyms for REGEXP and NOT REGEXP, originally provided for mSQL compatibility.

The pattern need not be a literal string. For example, it can be specified as a string expression or table column.

Note: Because MariaDB uses the C escape syntax in strings (for example, "\n" to represent the newline character), you must double any "\" that you use in your REGEXP strings.

REGEXP is not case sensitive, except when used with binary strings.

MariaDB 10.0.5 moved to the PCRE regex library - see PCRE Regular Expressions for enhancements to REGEXP introduced in MariaDB 10.0.5.

The default_regex_flags variable addresses the remaining compatibilities between PCRE and the old regex library.

Examples

SELECT 'Monty!' REGEXP 'm%y%%';
+-------------------------+
| 'Monty!' REGEXP 'm%y%%' |
+-------------------------+
|                       0 |
+-------------------------+

SELECT 'Monty!' REGEXP '.*';
+----------------------+
| 'Monty!' REGEXP '.*' |
+----------------------+
|                    1 |
+----------------------+

SELECT 'new*\n*line' REGEXP 'new\\*.\\*line';
+---------------------------------------+
| 'new*\n*line' REGEXP 'new\\*.\\*line' |
+---------------------------------------+
|                                     1 |
+---------------------------------------+

SELECT 'a' REGEXP 'A', 'a' REGEXP BINARY 'A';
+----------------+-----------------------+
| 'a' REGEXP 'A' | 'a' REGEXP BINARY 'A' |
+----------------+-----------------------+
|              1 |                     0 |
+----------------+-----------------------+

SELECT 'a' REGEXP '^[a-d]';
+---------------------+
| 'a' REGEXP '^[a-d]' |
+---------------------+
|                   1 |
+---------------------+

default_regex_flags examples

MariaDB 10.0.11 introduced the default_regex_flags variable to address the remaining compatibilities between PCRE and the old regex library.

The default behaviour (multiline match is off)

SELECT 'a\nb\nc' RLIKE '^b$';
+---------------------------+
| '(?m)a\nb\nc' RLIKE '^b$' |
+---------------------------+
|                         0 |
+---------------------------+

Enabling the multiline option using the PCRE option syntax:

SELECT 'a\nb\nc' RLIKE '(?m)^b$';
+---------------------------+
| 'a\nb\nc' RLIKE '(?m)^b$' |
+---------------------------+
|                         1 |
+---------------------------+

Enabling the multiline option using default_regex_flags

SET default_regex_flags='MULTILINE';
SELECT 'a\nb\nc' RLIKE '^b$';
+-----------------------+
| 'a\nb\nc' RLIKE '^b$' |
+-----------------------+
|                     1 |
+-----------------------+

1.2.2.1.5 REGEXP_INSTR

Syntax

REGEXP_INSTR(subject, pattern)

Returns the position of the first occurrence of the regular expression pattern in the string subject, or 0 if pattern was not found.

The positions start with 1 and are measured in characters (i.e. not in bytes), which is important for multi-byte character sets. You can cast a multi-byte character set to BINARY to get offsets in bytes.

The function follows the case sensitivity rules of the effective collation. Matching is performed case insensitively for case insensitive collations, and case sensitively for case sensitive collations and for binary data.

The collation case sensitivity can be overwritten using the (?i) and (?-i) PCRE flags.

MariaDB uses the PCRE regular expression library for enhanced regular expression performance, and REGEXP_INSTR was introduced as part of this enhancement.

Examples

SELECT REGEXP_INSTR('abc','b');
-> 2

SELECT REGEXP_INSTR('abc','x');
-> 0

SELECT REGEXP_INSTR('BJÖRN','N');
-> 5

Casting a multi-byte character set as BINARY to get offsets in bytes:

SELECT REGEXP_INSTR(BINARY 'BJÖRN','N') AS cast_utf8_to_binary;
-> 6

Case sensitivity:

SELECT REGEXP_INSTR('ABC','b');
-> 2

SELECT REGEXP_INSTR('ABC' COLLATE utf8_bin,'b');
-> 0

SELECT REGEXP_INSTR(BINARY'ABC','b');
-> 0

SELECT REGEXP_INSTR('ABC','(?-i)b');
-> 0

SELECT REGEXP_INSTR('ABC' COLLATE utf8_bin,'(?i)b');
-> 2

1.2.2.1.6 REGEXP_REPLACE

Syntax

REGEXP_REPLACE(subject, pattern, replace)

Description

REGEXP_REPLACE returns the string subject with all occurrences of the regular expression pattern replaced by the string replace. If no occurrences are found, then subject is returned as is.

The replace string can have backreferences to the subexpressions in the form \N, where N is a number from 1 to 9.

The function follows the case sensitivity rules of the effective collation. Matching is performed case insensitively for case insensitive collations, and case sensitively for case sensitive collations and for binary data.

The collation case sensitivity can be overwritten using the (?i) and (?-i) PCRE flags.

MariaDB uses the PCRE regular expression library for enhanced regular expression performance, and REGEXP_REPLACE was introduced as part of this enhancement.

The default_regex_flags variable addresses the remaining compatibilities between PCRE and the old regex library.

Examples

SELECT REGEXP_REPLACE('ab12cd','[0-9]','') AS remove_digits;
-> abcd

SELECT REGEXP_REPLACE('<html><head><title>title</title><body>body</body></htm>', '<.+?>',' ')
AS strip_html;
-> title  body

Backreferences to the subexpressions in the form \N, where N is a number from 1 to 9:

SELECT REGEXP_REPLACE('James Bond','^(.*) (.*)$','\\2, \\1') AS reorder_name;
-> Bond, James

Case insensitive and case sensitive matches:

SELECT REGEXP_REPLACE('ABC','b','-') AS case_insensitive;
-> A-C

SELECT REGEXP_REPLACE('ABC' COLLATE utf8_bin,'b','-') AS case_sensitive;
-> ABC

SELECT REGEXP_REPLACE(BINARY 'ABC','b','-') AS binary_data;
-> ABC

Overwriting the collation case sensitivity using the (?i) and (?-i) PCRE flags.

SELECT REGEXP_REPLACE('ABC','(?-i)b','-') AS force_case_sensitive;
-> ABC

SELECT REGEXP_REPLACE(BINARY 'ABC','(?i)b','-') AS force_case_insensitive;
-> A-C

1.2.2.1.7 REGEXP_SUBSTR

Syntax

REGEXP_SUBSTR(subject,pattern)

Description

Returns the part of the string subject that matches the regular expression pattern, or an empty string if pattern was not found.

The function follows the case sensitivity rules of the effective collation. Matching is performed case insensitively for case insensitive collations, and case sensitively for case sensitive collations and for binary data.

The collation case sensitivity can be overwritten using the (?i) and (?-i) PCRE flags.

MariaDB uses the PCRE regular expression library for enhanced regular expression performance, and REGEXP_SUBSTR was introduced as part of this enhancement.

The default_regex_flags variable addresses the remaining compatibilities between PCRE and the old regex library.

Examples

SELECT REGEXP_SUBSTR('ab12cd','[0-9]+');
-> 12

SELECT REGEXP_SUBSTR(
  'See https://mariadb.org/en/foundation/ for details',
  'https?://[^/]*');
-> https://mariadb.org

SELECT REGEXP_SUBSTR('ABC','b');
-> B

SELECT REGEXP_SUBSTR('ABC' COLLATE utf8_bin,'b');
->

SELECT REGEXP_SUBSTR(BINARY'ABC','b');
->

SELECT REGEXP_SUBSTR('ABC','(?i)b');
-> B

SELECT REGEXP_SUBSTR('ABC' COLLATE utf8_bin,'(?+i)b');
-> B

1.2.2.1.8 RLIKE

Syntax

expr REGEXP pat, expr RLIKE pat

Description

RLIKE is a synonym for REGEXP.

1.2.2.2 Dynamic Columns Functions

Dynamic columns is a feature that allows one to store different sets of columns for each row in a table. It works by storing a set of columns in a blob and having a small set of functions to manipulate it.

1.2.2.2.1 COLUMN_ADD

Syntax

COLUMN_ADD(dyncol_blob, column_nr, value [as type], [column_nr, value [as type]]...);
COLUMN_ADD(dyncol_blob, column_name, value [as type], [column_name, value [as type]]...);

Description

Adds or updates dynamic columns.

  • dyncol_blob must be either a valid dynamic columns blob (for example, COLUMN_CREATE returns such blob), or an empty string.
  • column_name specifies the name of the column to be added. If dyncol_blob already has a column with this name, it will be overwritten.
  • value specifies the new value for the column. Passing a NULL value will cause the column to be deleted.
  • as type is optional. See #datatypes section for a discussion about types.

The return value is a dynamic column blob after the modifications.

Examples

UPDATE t1 SET dyncol_blob=COLUMN_ADD(dyncol_blob, "column_name", "value") WHERE id=1;

Note: COLUMN_ADD() is a regular function (just like CONCAT()), hence, in order to update the value in the table you have to use the UPDATE ... SET dynamic_col=COLUMN_ADD(dynamic_col, ....) pattern.

1.2.2.2.2 COLUMN_CHECK

Syntax

COLUMN_CHECK(dyncol_blob);

Description

Check if dyncol_blob is a valid packed dynamic columns blob. Return value of 1 means the blob is valid, return value of 0 means it is not.

Rationale: Normally, one works with valid dynamic column blobs. Functions like COLUMN_CREATE, COLUMN_ADD, COLUMN_DELETE always return valid dynamic column blobs. However, if a dynamic column blob is accidentally truncated, or transcoded from one character set to another, it will be corrupted. This function can be used to check if a value in a blob field is a valid dynamic column blob.

1.2.2.2.3 COLUMN_CREATE

Syntax

COLUMN_CREATE(column_nr, value [as type], [column_nr, value [as type]]...);
COLUMN_CREATE(column_name, value [as type], [column_name, value [as type]]...);

Description

Returns a dynamic columns blob that stores the specified columns with values.

The return value is suitable for

  • storing in a table
  • further modification with other dynamic columns functions

The as type part allows one to specify the value type. In most cases, this is redundant because MariaDB will be able to deduce the type of the value. Explicit type specification may be needed when the type of the value is not apparent. For example, a literal '2012-12-01' has a CHAR type by default, one will need to specify '2012-12-01' AS DATE to have it stored as a date. See Dynamic Columns:Datatypes for further details.

Examples

INSERT INTO tbl SET dyncol_blob=COLUMN_CREATE("column_name", "value");

1.2.2.2.4 COLUMN_DELETE

Syntax

COLUMN_DELETE(dyncol_blob, column_nr, column_nr...);
COLUMN_DELETE(dyncol_blob, column_name, column_name...);

Description

Deletes a dynamic column with the specified name. Multiple names can be given. The return value is a dynamic column blob after the modification.

1.2.2.2.5 COLUMN_EXISTS

Syntax

COLUMN_EXISTS(dyncol_blob, column_nr);
COLUMN_EXISTS(dyncol_blob, column_name);

Description

Checks if a column with name column_name exists in dyncol_blob. If yes, return 1, otherwise return 0. See dynamic columns for more information.

1.2.2.2.6 COLUMN_GET

Syntax

COLUMN_GET(dyncol_blob, column_nr as type);
COLUMN_GET(dyncol_blob, column_name as type);

Description

Gets the value of a dynamic column by its name. If no column with the given name exists, NULL will be returned.

column_name as type requires that one specify the datatype of the dynamic column they are reading.

This may seem counter-intuitive: why would one need to specify which datatype they're retrieving? Can't the dynamic columns system figure the datatype from the data being stored?

The answer is: SQL is a statically-typed language. The SQL interpreter needs to know the datatypes of all expressions before the query is run (for example, when one is using prepared statements and runs "select COLUMN_GET(...)", the prepared statement API requires the server to inform the client about the datatype of the column being read before the query is executed and the server can see what datatype the column actually has).

Lengths

If you're running queries like:

SELECT COLUMN_GET(blob, 'colname' as CHAR) ...

without specifying a maximum length (i.e. using as CHAR, not as CHAR(n)), MariaDB will report the maximum length of the resultset column to be 16,777,216. This may cause excessive memory usage in some client libraries, because they try to pre-allocate a buffer of maximum resultset width. To avoid this problem, use CHAR(n) whenever you're using COLUMN_GET in the select list.

See Dynamic Columns:Datatypes for more information about datatypes.

1.2.2.2.7 COLUMN_JSON

Syntax

COLUMN_JSON(dyncol_blob)

Description

Returns a JSON representation of data in dyncol_blob. Can also be used to display nested columns. See dynamic columns for more information.

Example

select item_name, COLUMN_JSON(dynamic_cols) from assets;
+-----------------+----------------------------------------+
| item_name       | COLUMN_JSON(dynamic_cols)              |
+-----------------+----------------------------------------+
| MariaDB T-shirt | {"size":"XL","color":"blue"}           |
| Thinkpad Laptop | {"color":"black","warranty":"3 years"} |
+-----------------+----------------------------------------+

Limitation: COLUMN_JSON will decode nested dynamic columns at a nesting level of not more than 10 levels deep. Dynamic columns that are nested deeper than 10 levels will be shown as BINARY string, without encoding.

1.2.2.2.8 COLUMN_LIST

Syntax

COLUMN_LIST(dyncol_blob);

Description

Returns a comma-separated list of column names. The names are quoted with backticks.

See dynamic columns for more information.

1.2.2.3 ASCII

Syntax

ASCII(str)

Description

Returns the numeric ASCII value of the leftmost character of the string argument. Returns 0 if the given string is empty and NULL if it is NULL.

ASCII() works for 8-bit characters.

Examples

SELECT ASCII(9);
+----------+
| ASCII(9) |
+----------+
|       57 |
+----------+

SELECT ASCII('9');
+------------+
| ASCII('9') |
+------------+
|         57 |
+------------+

SELECT ASCII('abc');
+--------------+
| ASCII('abc') |
+--------------+
|           97 |
+--------------+

1.2.2.4 BIN

Syntax

BIN(N)

Description

Returns a string representation of the binary value of the given longlong (that is, BIGINT) number. This is equivalent to CONV(N,10,2). The argument should be positive. If it is a FLOAT, it will be truncated. Returns NULL if the argument is NULL.

Examples

SELECT BIN(12);
+---------+
| BIN(12) |
+---------+
| 1100    |
+---------+

See Also

1.2.2.5 BINARY Operator

This page describes the BINARY operator. For details about the data type, see Binary Data Type.

Syntax

BINARY

Description

The BINARY operator casts the string following it to a binary string. This is an easy way to force a column comparison to be done byte by byte rather than character by character. This causes the comparison to be case sensitive even if the column isn't defined as BINARY or BLOB.

BINARY also causes trailing spaces to be significant.

Examples

SELECT 'a' = 'A';
+-----------+
| 'a' = 'A' |
+-----------+
|         1 |
+-----------+

SELECT BINARY 'a' = 'A';
+------------------+
| BINARY 'a' = 'A' |
+------------------+
|                0 |
+------------------+

SELECT 'a' = 'a ';
+------------+
| 'a' = 'a ' |
+------------+
|          1 |
+------------+

SELECT BINARY 'a' = 'a ';
+-------------------+
| BINARY 'a' = 'a ' |
+-------------------+
|                 0 |
+-------------------+

1.2.2.6 BIT_LENGTH

Syntax

BIT_LENGTH(str)

Contents

  1. Syntax
  2. Description
  3. Examples
  4. Compatibility

Description

Returns the length of the given string argument in bits. If the argument is not a string, it will be converted to string. If the argument is NULL, it returns NULL.

Examples

SELECT BIT_LENGTH('text');
+--------------------+
| BIT_LENGTH('text') |
+--------------------+
|                 32 |
+--------------------+

SELECT BIT_LENGTH('');
+----------------+
| BIT_LENGTH('') |
+----------------+
|              0 |
+----------------+

Compatibility

PostgreSQL and Sybase support BIT_LENGTH().

1.2.2.7 CAST

Syntax

CAST(expr AS type)

Contents

  1. Syntax
  2. Description
  3. Examples
  4. See Also

Description

The CAST() function takes a value of one type and produces a value of another type, similar to the CONVERT() function.

The type can be one of the following values:

The main difference between CAST and CONVERT() is that CONVERT(expr,type) is ODBC syntax while CAST(expr as type) and CONVERT(... USING ...) are SQL92 syntax.

In MariaDB 10.4 and later, you can use the CAST() function with the INTERVAL keyword.

Until MariaDB 5.5.31, X'HHHH', the standard SQL syntax for binary string literals, erroneously worked in the same way as 0xHHHH. In 5.5.31 it was intentionally changed to behave as a string in all contexts (and never as a number).

This introduced an incompatibility with previous versions of MariaDB, and all versions of MySQL (see the example below).

Examples

Simple casts:

SELECT CAST("abc" AS BINARY);
SELECT CAST("1" AS UNSIGNED INTEGER);
SELECT CAST(123 AS CHAR CHARACTER SET utf8)

Note that when one casts to CHAR without specifying the character set, the collation_connection character set collation will be used. When used with CHAR CHARACTER SET, the default collation for that character set will be used.

SELECT COLLATION(CAST(123 AS CHAR));
+------------------------------+
| COLLATION(CAST(123 AS CHAR)) |
+------------------------------+
| latin1_swedish_ci            |
+------------------------------+

SELECT COLLATION(CAST(123 AS CHAR CHARACTER SET utf8));
+-------------------------------------------------+
| COLLATION(CAST(123 AS CHAR CHARACTER SET utf8)) |
+-------------------------------------------------+
| utf8_general_ci                                 |
+-------------------------------------------------+

If you also want to change the collation, you have to use the COLLATE operator:

SELECT COLLATION(CAST(123 AS CHAR CHARACTER SET utf8) 
  COLLATE utf8_unicode_ci);
+-------------------------------------------------------------------------+
| COLLATION(CAST(123 AS CHAR CHARACTER SET utf8) COLLATE utf8_unicode_ci) |
+-------------------------------------------------------------------------+
| utf8_unicode_ci                                                         |
+-------------------------------------------------------------------------+

Using CAST() to order an ENUM field as a CHAR rather than the internal numerical value:

CREATE TABLE enum_list (enum_field enum('c','a','b'));

INSERT INTO enum_list (enum_field) 
VALUES('c'),('a'),('c'),('b');

SELECT * FROM enum_list 
ORDER BY enum_field;
+------------+
| enum_field |
+------------+
| c          |
| c          |
| a          |
| b          |
+------------+

SELECT * FROM enum_list 
ORDER BY CAST(enum_field AS CHAR);
+------------+
| enum_field |
+------------+
| a          |
| b          |
| c          |
| c          |
+------------+

From MariaDB 5.5.31, the following will trigger warnings, since x'aa' and 'X'aa' no longer behave as a number. Previously, and in all versions of MySQL, no warnings are triggered since they did erroneously behave as a number:

SELECT CAST(0xAA AS UNSIGNED), CAST(x'aa' AS UNSIGNED), CAST(X'aa' AS UNSIGNED);
+------------------------+-------------------------+-------------------------+
| CAST(0xAA AS UNSIGNED) | CAST(x'aa' AS UNSIGNED) | CAST(X'aa' AS UNSIGNED) |
+------------------------+-------------------------+-------------------------+
|                    170 |                       0 |                       0 |
+------------------------+-------------------------+-------------------------+
1 row in set, 2 warnings (0.00 sec)

Warning (Code 1292): Truncated incorrect INTEGER value: '\xAA'
Warning (Code 1292): Truncated incorrect INTEGER value: '\xAA'

Casting to intervals:

SELECT CAST(2019-01-04 INTERVAL AS DAY_SECOND(2)) AS "Cast";

+-------------+
| Cast        |
+-------------+
| 00:20:17.00 |
+-------------+

See Also

1.2.2.8 CHAR Function

Syntax

CHAR(N,... [USING charset_name])

Description

CHAR() interprets each argument as an INT and returns a string consisting of the characters given by the code values of those integers. NULL values are skipped. By default, CHAR() returns a binary string. To produce a string in a given character set, use the optional USING clause:

SELECT CHARSET(CHAR(0x65)), CHARSET(CHAR(0x65 USING utf8));
+---------------------+--------------------------------+
| CHARSET(CHAR(0x65)) | CHARSET(CHAR(0x65 USING utf8)) |
+---------------------+--------------------------------+
| binary              | utf8                           |
+---------------------+--------------------------------+

If USING is given and the result string is illegal for the given character set, a warning is issued. Also, if strict SQL mode is enabled, the result from CHAR() becomes NULL.

Examples

SELECT CHAR(77,97,114,'105',97,'68',66);
+----------------------------------+
| CHAR(77,97,114,'105',97,'68',66) |
+----------------------------------+
| MariaDB                          |
+----------------------------------+

SELECT CHAR(77,77.3,'77.3');
+----------------------+
| CHAR(77,77.3,'77.3') |
+----------------------+
| MMM                  |
+----------------------+
1 row in set, 1 warning (0.00 sec)

Warning (Code 1292): Truncated incorrect INTEGER value: '77.3'

See Also

1.2.2.9 CHAR_LENGTH

Syntax

CHAR_LENGTH(str)
CHARACTER_LENGTH(str)

Contents

  1. Syntax
  2. Description
  3. Examples
  4. See Also

Description

Returns the length of the given string argument, measured in characters. A multi-byte character counts as a single character. This means that for a string containing five two-byte characters, LENGTH() (or OCTET_LENGTH() in Oracle mode) returns 10, whereas CHAR_LENGTH() returns 5. If the argument is NULL, it returns NULL.

If the argument is not a string value, it is converted into a string.

It is synonymous with the CHARACTER_LENGTH() function.

Examples

SELECT CHAR_LENGTH('MariaDB');
+------------------------+
| CHAR_LENGTH('MariaDB') |
+------------------------+
|                      7 |
+------------------------+

When Oracle mode from MariaDB 10.3 is not set:

SELECT CHAR_LENGTH('π'), LENGTH('π'), LENGTHB('π'), OCTET_LENGTH('π');
+-------------------+--------------+---------------+--------------------+
| CHAR_LENGTH('π')  | LENGTH('π')  | LENGTHB('π')  | OCTET_LENGTH('π')  |
+-------------------+--------------+---------------+--------------------+
|                 1 |            2 |             2 |                  2 |
+-------------------+--------------+---------------+--------------------+

In Oracle mode from MariaDB 10.3:

SELECT CHAR_LENGTH('π'), LENGTH('π'), LENGTHB('π'), OCTET_LENGTH('π');
+-------------------+--------------+---------------+--------------------+
| CHAR_LENGTH('π')  | LENGTH('π')  | LENGTHB('π')  | OCTET_LENGTH('π')  |
+-------------------+--------------+---------------+--------------------+
|                 1 |            1 |             2 |                  2 |
+-------------------+--------------+---------------+--------------------+

See Also

1.2.2.10 CHARACTER_LENGTH

Syntax

CHARACTER_LENGTH(str)

Description

CHARACTER_LENGTH() is a synonym for CHAR_LENGTH().

1.2.2.11 CHR

MariaDB starting with 10.3.1

The CHR() function was introduced in MariaDB 10.3.1 to provide Oracle compatibility

Syntax

CHR(N)

Description

CHR() interprets each argument N as an integer and returns a VARCHAR(1) string consisting of the character given by the code values of the integer. The character set and collation of the string are set according to the values of the character_set_database and collation_database system variables.

CHR() is similar to the CHAR() function, but only accepts a single argument.

CHR() is available in all sql_modes.

Examples

SELECT CHR(67);
+---------+
| CHR(67) |
+---------+
| C       |
+---------+

SELECT CHR('67');
+-----------+
| CHR('67') |
+-----------+
| C         |
+-----------+

SELECT CHR('C');
+----------+
| CHR('C') |
+----------+
|          |
+----------+
1 row in set, 1 warning (0.000 sec)

SHOW WARNINGS;
+---------+------+----------------------------------------+
| Level   | Code | Message                                |
+---------+------+----------------------------------------+
| Warning | 1292 | Truncated incorrect INTEGER value: 'C' |
+---------+------+----------------------------------------+

See Also

1.2.2.12 CONCAT

Syntax

CONCAT(str1,str2,...)

Contents

  1. Syntax
  2. Description
    1. Oracle Mode
  3. Examples
  4. See Also

Description

Returns the string that results from concatenating the arguments. May have one or more arguments. If all arguments are non-binary strings, the result is a non-binary string. If the arguments include any binary strings, the result is a binary string. A numeric argument is converted to its equivalent binary string form; if you want to avoid that, you can use an explicit type cast, as in this example:

SELECT CONCAT(CAST(int_col AS CHAR), char_col);

CONCAT() returns NULL if any argument is NULL.

A NULL parameter hides all information contained in other parameters from the result. Sometimes this is not desirable; to avoid this, you can:

  • Use the CONCAT_WS() function with an empty separator, because that function is NULL-safe.
  • Use IFNULL() to turn NULLs into empty strings.

Oracle Mode

MariaDB starting with 10.3

In Oracle mode from MariaDB 10.3, CONCAT ignores NULL.

Examples

SELECT CONCAT('Ma', 'ria', 'DB');
+---------------------------+
| CONCAT('Ma', 'ria', 'DB') |
+---------------------------+
| MariaDB                   |
+---------------------------+

SELECT CONCAT('Ma', 'ria', NULL, 'DB');
+---------------------------------+
| CONCAT('Ma', 'ria', NULL, 'DB') |
+---------------------------------+
| NULL                            |
+---------------------------------+

SELECT CONCAT(42.0);
+--------------+
| CONCAT(42.0) |
+--------------+
| 42.0         |
+--------------+

Using IFNULL() to handle NULLs:

SELECT CONCAT('The value of @v is: ', IFNULL(@v, ''));
+------------------------------------------------+
| CONCAT('The value of @v is: ', IFNULL(@v, '')) |
+------------------------------------------------+
| The value of @v is:                            |
+------------------------------------------------+

In Oracle mode, from MariaDB 10.3:

SELECT CONCAT('Ma', 'ria', NULL, 'DB');
+---------------------------------+
| CONCAT('Ma', 'ria', NULL, 'DB') |
+---------------------------------+
| MariaDB                         |
+---------------------------------+

See Also

1.2.2.13 CONCAT_WS

Syntax

CONCAT_WS(separator,str1,str2,...)

Description

CONCAT_WS() stands for Concatenate With Separator and is a special form of CONCAT(). The first argument is the separator for the rest of the arguments. The separator is added between the strings to be concatenated. The separator can be a string, as can the rest of the arguments.

If the separator is NULL, the result is NULL; all other NULL values are skipped. This makes CONCAT_WS() suitable when you want to concatenate some values and avoid losing all information if one of them is NULL.

Examples

SELECT CONCAT_WS(',','First name','Second name','Last Name');
+-------------------------------------------------------+
| CONCAT_WS(',','First name','Second name','Last Name') |
+-------------------------------------------------------+
| First name,Second name,Last Name                      |
+-------------------------------------------------------+

SELECT CONCAT_WS('-','Floor',NULL,'Room');
+------------------------------------+
| CONCAT_WS('-','Floor',NULL,'Room') |
+------------------------------------+
| Floor-Room                         |
+------------------------------------+

In some cases, remember to include a space in the separator string:

SET @a = 'gnu', @b = 'penguin', @c = 'sea lion';
Query OK, 0 rows affected (0.00 sec)

SELECT CONCAT_WS(', ', @a, @b, @c);
+-----------------------------+
| CONCAT_WS(', ', @a, @b, @c) |
+-----------------------------+
| gnu, penguin, sea lion      |
+-----------------------------+

Using CONCAT_WS() to handle NULLs:

SET @a = 'a', @b = NULL, @c = 'c';

SELECT CONCAT_WS('', @a, @b, @c);
+---------------------------+
| CONCAT_WS('', @a, @b, @c) |
+---------------------------+
| ac                        |
+---------------------------+

See Also

1.2.2.14 CONVERT

Syntax

CONVERT(expr,type), CONVERT(expr USING transcoding_name)

Contents

  1. Syntax
  2. Description
  3. Examples
  4. See Also

Description

The CONVERT() and CAST() functions take a value of one type and produce a value of another type.

The type can be one of the following values:

Note that in MariaDB, INT and INTEGER are the same thing.

BINARY produces a string with the BINARY data type. If the optional length is given, BINARY(N) causes the cast to use no more than N bytes of the argument. Values shorter than the given number in bytes are padded with 0x00 bytes to make them equal the length value.

CHAR(N) causes the cast to use no more than the number of characters given in the argument.

The main difference between the CAST() and CONVERT() is that CONVERT(expr,type) is ODBC syntax while CAST(expr as type) and CONVERT(... USING ...) are SQL92 syntax.

CONVERT() with USING is used to convert data between different character sets. In MariaDB, transcoding names are the same as the corresponding character set names. For example, this statement converts the string 'abc' in the default character set to the corresponding string in the utf8 character set:

SELECT CONVERT('abc' USING utf8);

Examples

SELECT enum_col FROM tbl_name 
ORDER BY CAST(enum_col AS CHAR);

Converting a BINARY to string to permit the LOWER function to work:

SET @x = 'AardVark';

SET @x = BINARY 'AardVark';

SELECT LOWER(@x), LOWER(CONVERT (@x USING latin1));
+-----------+----------------------------------+
| LOWER(@x) | LOWER(CONVERT (@x USING latin1)) |
+-----------+----------------------------------+
| AardVark  | aardvark                         |
+-----------+----------------------------------+

See Also

1.2.2.15 ELT

Syntax

ELT(N, str1[, str2, str3,...])

Description

Takes a numeric argument and a series of string arguments. Returns the string that corresponds to the given numeric position. For instance, it returns str1 if N is 1, str2 if N is 2, and so on. If the numeric argument is a FLOAT, MariaDB rounds it to the nearest INTEGER. If the numeric argument is less than 1, greater than the total number of arguments, or not a number, ELT() returns NULL. It must have at least two arguments.

It is complementary to the FIELD() function.

Examples

SELECT ELT(1, 'ej', 'Heja', 'hej', 'foo');
+------------------------------------+
| ELT(1, 'ej', 'Heja', 'hej', 'foo') |
+------------------------------------+
| ej                                 |
+------------------------------------+

SELECT ELT(4, 'ej', 'Heja', 'hej', 'foo');
+------------------------------------+
| ELT(4, 'ej', 'Heja', 'hej', 'foo') |
+------------------------------------+
| foo                                |
+------------------------------------+

See also

  • FIND_IN_SET() function. Returns the position of a string in a set of strings.
  • FIELD() function. Returns the index position of a string in a list.

1.2.2.16 EXPORT_SET

Syntax

EXPORT_SET(bits, on, off[, separator[, number_of_bits]])

Description

Takes a minimum of three arguments. Returns a string where each bit in the given bits argument is returned, with the string values given for on and off.

Bits are examined from right to left, (from low-order to high-order bits). Strings are added to the result from left to right, separated by a separator string (defaults as ','). You can optionally limit the number of bits the EXPORT_SET() function examines using the number_of_bits option.

If any of the arguments are set as NULL, the function returns NULL.

Examples

SELECT EXPORT_SET(5,'Y','N',',',4);
+-----------------------------+
| EXPORT_SET(5,'Y','N',',',4) |
+-----------------------------+
| Y,N,Y,N                     |
+-----------------------------+

SELECT EXPORT_SET(6,'1','0',',',10);
+------------------------------+
| EXPORT_SET(6,'1','0',',',10) |
+------------------------------+
| 0,1,1,0,0,0,0,0,0,0          |
+------------------------------+

1.2.2.17 EXTRACTVALUE

Syntax

EXTRACTVALUE(xml_frag, xpath_expr)

Contents

  1. Syntax
  2. Description
    1. Invalid Arguments
    2. Explicit text() Expressions
    3. Count Matches
    4. Matches
  3. Examples

Description

The EXTRACTVALUE() function takes two string arguments: a fragment of XML markup and an XPath expression, (also known as a locator). It returns the text (That is, CDDATA), of the first text node which is a child of the element or elements matching the XPath expression.

In cases where a valid XPath expression does not match any text nodes in a valid XML fragment, (including the implicit /text() expression), the EXTRACTVALUE() function returns an empty string.

Invalid Arguments

When either the XML fragment or the XPath expression is NULL, the EXTRACTVALUE() function returns NULL. When the XML fragment is invalid, it raises a warning Code 1525:

Warning (Code 1525): Incorrect XML value: 'parse error at line 1 pos 11: unexpected END-OF-INPUT'

When the XPath value is invalid, it generates an Error 1105:

ERROR 1105 (HY000): XPATH syntax error: ')'

Explicit text() Expressions

This function is the equivalent of performing a match using the XPath expression after appending /text(). In other words:

SELECT
   EXTRACTVALUE('<cases><case>example</case></cases>', '/cases/case') AS 'Base Example',
   EXTRACTVALUE('<cases><case>example</case></cases>', '/cases/case/text()') AS 'text() Example';

+--------------+----------------+
| Base Example | text() Example |
+--------------+----------------+
| example      | example        |
+--------------+----------------+

Count Matches

When EXTRACTVALUE() returns multiple matches, it returns the content of the first child text node of each matching element, in the matched order, as a single, space-delimited string.

By design, the EXTRACTVALUE() function makes no distinction between a match on an empty element and no match at all. If you need to determine whether no matching element was found in the XML fragment or if an element was found that contained no child text nodes, use the XPath count() function.

For instance, when looking for a value that exists, but contains no child text nodes, you would get a count of the number of matching instances:

SELECT
   EXTRACTVALUE('<cases><case/></cases>', '/cases/case') AS 'Empty Example',
   EXTRACTVALUE('<cases><case/></cases>', 'count(/cases/case)') AS 'count() Example';

+---------------+-----------------+
| Empty Example | count() Example |
+---------------+-----------------+
|               |               1 |
+---------------+-----------------+

Alternatively, when looking for a value that doesn't exist, count() returns 0.

SELECT
   EXTRACTVALUE('<cases><case/></cases>', '/cases/person') AS 'No Match Example',
   EXTRACTVALUE('<cases><case/></cases>', 'count(/cases/person)') AS 'count() Example';

+------------------+-----------------+
| No Match Example | count() Example |
+------------------+-----------------+
|                  |                0|
+------------------+-----------------+

Matches

Important: The EXTRACTVALUE() function only returns CDDATA. It does not return tags that the element might contain or the text that these child elements contain.

SELECT EXTRACTVALUE('<cases><case>Person<email>x@example.com</email></case></cases>', '/cases') AS Case;

+--------+
| Case   |
+--------+
| Person |
+--------+

Note, in the above example, while the XPath expression matches to the parent <case> instance, it does not return the contained <email> tag or its content.

Examples

SELECT
    ExtractValue('<a>ccc<b>ddd</b></a>', '/a')            AS val1,
    ExtractValue('<a>ccc<b>ddd</b></a>', '/a/b')          AS val2,
    ExtractValue('<a>ccc<b>ddd</b></a>', '//b')           AS val3,
    ExtractValue('<a>ccc<b>ddd</b></a>', '/b')            AS val4,
    ExtractValue('<a>ccc<b>ddd</b><b>eee</b></a>', '//b') AS val5;
+------+------+------+------+---------+
| val1 | val2 | val3 | val4 | val5    |
+------+------+------+------+---------+
| ccc  | ddd  | ddd  |      | ddd eee |
+------+------+------+------+---------+

1.2.2.18 FIELD

Syntax

FIELD(pattern, str1[,str2,...])

Description

Returns the index position of the string or number matching the given pattern. Returns 0 in the event that none of the arguments match the pattern. Raises an Error 1582 if not given at least two arguments.

When all arguments given to the FIELD() function are strings, they are treated as case-insensitive. When all the arguments are numbers, they are treated as numbers. Otherwise, they are treated as doubles.

If the given pattern occurs more than once, the FIELD() function only returns the index of the first instance. If the given pattern is NULL, the function returns 0, as a NULL pattern always fails to match.

This function is complementary to the ELT() function.

Examples

SELECT FIELD('ej', 'Hej', 'ej', 'Heja', 'hej', 'foo') 
   AS 'Field Results';
+---------------+
| Field Results | 
+---------------+
|             2 |
+---------------+

SELECT FIELD('fo', 'Hej', 'ej', 'Heja', 'hej', 'foo')
   AS 'Field Results';
+---------------+
| Field Results | 
+---------------+
|             0 |
+---------------+

SELECT FIELD(1, 2, 3, 4, 5, 1) AS 'Field Results';
+---------------+
| Field Results |
+---------------+
|             5 |
+---------------+

SELECT FIELD(NULL, 2, 3) AS 'Field Results';
+---------------+
| Field Results |
+---------------+
|             0 |
+---------------+

SELECT FIELD('fail') AS 'Field Results';
Error 1582 (42000): Incorrect parameter count in call
to native function 'field'

See also

  • ELT() function. Returns the N'th element from a set of strings.

1.2.2.19 FIND_IN_SET

Syntax

FIND_IN_SET(pattern, strlist)

Description

Returns the index position where the given pattern occurs in a string list. The first argument is the pattern you want to search for. The second argument is a string containing comma-separated variables. If the second argument is of the SET data-type, the function is optimized to use bit arithmetic.

If the pattern does not occur in the string list or if the string list is an empty string, the function returns 0. If either argument is NULL, the function returns NULL. The function does not return the correct result if the pattern contains a comma (",") character.

Examples

SELECT FIND_IN_SET('b','a,b,c,d') AS "Found Results";
+---------------+
| Found Results |
+---------------+
|             2 |
+---------------+

See Also

  • ELT() function. Returns the N'th element from a set of strings.

1.2.2.20 FORMAT

Syntax

FORMAT(num, decimal_position[, locale])

Description

Formats the given number for display as a string, adding separators to appropriate position and rounding the results to the given decimal position. For instance, it would format 15233.345 to 15,233.35.

If the given decimal position is 0, it rounds to return no decimal point or fractional part. You can optionally specify a locale value to format numbers to the pattern appropriate for the given region.

Examples

SELECT FORMAT(1234567890.09876543210, 4) AS 'Format';
+--------------------+
| Format             |
+--------------------+
| 1,234,567,890.0988 |
+--------------------+

SELECT FORMAT(1234567.89, 4) AS 'Format';
+----------------+
| Format         |
+----------------+
| 1,234,567.8900 |
+----------------+

SELECT FORMAT(1234567.89, 0) AS 'Format';
+-----------+
| Format    |
+-----------+
| 1,234,568 |
+-----------+

SELECT FORMAT(123456789,2,'rm_CH') AS 'Format';
+----------------+
| Format         |
+----------------+
| 123'456'789,00 |
+----------------+

1.2.2.21 FROM_BASE64

Syntax

FROM_BASE64(str)

Description

Decodes the given base-64 encode string, returning the result as a binary string. Returns NULL if the given string is NULL or if it's invalid.

It is the reverse of the TO_BASE64 function.

There are numerous methods to base-64 encode a string. MariaDB uses the following:

  • It encodes alphabet value 64 as '+'.
  • It encodes alphabet value 63 as '/'.
  • It codes output in groups of four printable characters. Each three byte of data encoded uses four characters. If the final group is incomplete, it pads the difference with the '=' character.
  • It divides long output, adding a new line very 76 characters.
  • In decoding, it recognizes and ignores newlines, carriage returns, tabs and space whitespace characters. 
SELECT TO_BASE64('Maria') AS 'Input';
+-----------+
| Input     |
+-----------+
| TWFyaWE=  |
+-----------+

SELECT FROM_BASE64('TWFyaWE=') AS 'Output';
+--------+
| Output |
+--------+
| Maria  |
+--------+

1.2.2.22 HEX

Syntax

HEX(N_or_S)

Description

If N_or_S is a number, returns a string representation of the hexadecimal value of N, where N is a longlong (BIGINT) number. This is equivalent to CONV(N,10,16).

If N_or_S is a string, returns a hexadecimal string representation of N_or_S where each byte of each character in N_or_S is converted to two hexadecimal digits. If N_or_S is NULL, returns NULL. The inverse of this operation is performed by the UNHEX() function.


MariaDB starting with 10.5.0

HEX() with an INET6 argument returns a hexadecimal representation of the underlying 16-byte binary string.

Examples

SELECT HEX(255);
+----------+
| HEX(255) |
+----------+
| FF       |
+----------+

SELECT 0x4D617269614442;
+------------------+
| 0x4D617269614442 |
+------------------+
| MariaDB          |
+------------------+

SELECT HEX('MariaDB');
+----------------+
| HEX('MariaDB') |
+----------------+
| 4D617269614442 |
+----------------+

From MariaDB 10.5.0:

SELECT HEX(CAST('2001:db8::ff00:42:8329' AS INET6));
+----------------------------------------------+
| HEX(CAST('2001:db8::ff00:42:8329' AS INET6)) |
+----------------------------------------------+
| 20010DB8000000000000FF0000428329             |
+----------------------------------------------+

See Also

1.2.2.23 INSERT Function

Syntax

INSERT(str,pos,len,newstr)

Description

Returns the string str, with the substring beginning at position pos and len characters long replaced by the string newstr. Returns the original string if pos is not within the length of the string. Replaces the rest of the string from position pos if len is not within the length of the rest of the string. Returns NULL if any argument is NULL.

Examples

SELECT INSERT('Quadratic', 3, 4, 'What');
+-----------------------------------+
| INSERT('Quadratic', 3, 4, 'What') |
+-----------------------------------+
| QuWhattic                         |
+-----------------------------------+

SELECT INSERT('Quadratic', -1, 4, 'What');
+------------------------------------+
| INSERT('Quadratic', -1, 4, 'What') |
+------------------------------------+
| Quadratic                          |
+------------------------------------+

SELECT INSERT('Quadratic', 3, 100, 'What');
+-------------------------------------+
| INSERT('Quadratic', 3, 100, 'What') |
+-------------------------------------+
| QuWhat                              |
+-------------------------------------+

1.2.2.24 LENGTH

Syntax

LENGTH(str)

Contents

  1. Syntax
  2. Description
  3. Examples
  4. See Also

Description

Returns the length of the string str.

In the default mode, when Oracle mode from MariaDB 10.3 is not set, the length is measured in bytes. In this case, a multi-byte character counts as multiple bytes. This means that for a string containing five two-byte characters, LENGTH() returns 10, whereas CHAR_LENGTH() returns 5.

When running Oracle mode from MariaDB 10.3, the length is measured in characters, and LENGTH is a synonym for CHAR_LENGTH().

If str is not a string value, it is converted into a string. If str is NULL, the function returns NULL.

Examples

SELECT LENGTH('MariaDB');
+-------------------+
| LENGTH('MariaDB') |
+-------------------+
|                 7 |
+-------------------+

When Oracle mode from MariaDB 10.3 is not set:

SELECT CHAR_LENGTH('π'), LENGTH('π'), LENGTHB('π'), OCTET_LENGTH('π');
+-------------------+--------------+---------------+--------------------+
| CHAR_LENGTH('π')  | LENGTH('π')  | LENGTHB('π')  | OCTET_LENGTH('π')  |
+-------------------+--------------+---------------+--------------------+
|                 1 |            2 |             2 |                  2 |
+-------------------+--------------+---------------+--------------------+

In Oracle mode from MariaDB 10.3:

SELECT CHAR_LENGTH('π'), LENGTH('π'), LENGTHB('π'), OCTET_LENGTH('π');
+-------------------+--------------+---------------+--------------------+
| CHAR_LENGTH('π')  | LENGTH('π')  | LENGTHB('π')  | OCTET_LENGTH('π')  |
+-------------------+--------------+---------------+--------------------+
|                 1 |            1 |             2 |                  2 |
+-------------------+--------------+---------------+--------------------+

See Also

1.2.2.25 LENGTHB

MariaDB starting with 10.3.1

Introduced in MariaDB 10.3.1 as part of the Oracle compatibility enhancements.

Syntax

LENGTHB(str)

Description

LENGTHB() returns the length of the given string, in bytes. When Oracle mode is not set, this is a synonym for LENGTH.

A multi-byte character counts as multiple bytes. This means that for a string containing five two-byte characters, LENGTHB() returns 10, whereas CHAR_LENGTH() returns 5.

If str is not a string value, it is converted into a string. If str is NULL, the function returns NULL.

Examples

When Oracle mode from MariaDB 10.3 is not set:

SELECT CHAR_LENGTH('π'), LENGTH('π'), LENGTHB('π'), OCTET_LENGTH('π');
+-------------------+--------------+---------------+--------------------+
| CHAR_LENGTH('π')  | LENGTH('π')  | LENGTHB('π')  | OCTET_LENGTH('π')  |
+-------------------+--------------+---------------+--------------------+
|                 1 |            2 |             2 |                  2 |
+-------------------+--------------+---------------+--------------------+

In Oracle mode from MariaDB 10.3:

SELECT CHAR_LENGTH('π'), LENGTH('π'), LENGTHB('π'), OCTET_LENGTH('π');
+-------------------+--------------+---------------+--------------------+
| CHAR_LENGTH('π')  | LENGTH('π')  | LENGTHB('π')  | OCTET_LENGTH('π')  |
+-------------------+--------------+---------------+--------------------+
|                 1 |            1 |             2 |                  2 |
+-------------------+--------------+---------------+--------------------+

See Also

1.2.2.26 LIKE

Syntax

expr LIKE pat [ESCAPE 'escape_char']
expr NOT LIKE pat [ESCAPE 'escape_char']

Contents

  1. Syntax
  2. Description
  3. Examples
  4. Optimizing LIKE
  5. See Also

Description

Tests whether expr matches the pattern pat. Returns either 1 (TRUE) or 0 (FALSE). Both expr and pat may be any valid expression and are evaluated to strings. Patterns may use the following wildcard characters:

  • % matches any number of characters, including zero.
  • _ matches any single character.

Use NOT LIKE to test if a string does not match a pattern. This is equivalent to using the NOT operator on the entire LIKE expression.

If either the expression or the pattern is NULL, the result is NULL.

LIKE performs case-insensitive substring matches if the collation for the expression and pattern is case-insensitive. For case-sensitive matches, declare either argument to use a binary collation using COLLATE, or coerce either of them to a BINARY string using CAST. Use SHOW COLLATION to get a list of available collations. Collations ending in _bin are case-sensitive.

Numeric arguments are coerced to binary strings.

The _ wildcard matches a single character, not byte. It will only match a multi-byte character if it is valid in the expression's character set. For example, _ will match _utf8"€", but it will not match _latin1"€" because the Euro sign is not a valid latin1 character. If necessary, use CONVERT to use the expression in a different character set.

If you need to match the characters _ or %, you must escape them. By default, you can prefix the wildcard characters the backslash character \ to escape them. The backslash is used both to encode special characters like newlines when a string is parsed as well as to escape wildcards in a pattern after parsing. Thus, to match an actual backslash, you sometimes need to double-escape it as "\\\\".

To avoid difficulties with the backslash character, you can change the wildcard escape character using ESCAPE in a LIKE expression. The argument to ESCAPE must be a single-character string.

Examples

Select the days that begin with "T":

CREATE TABLE t1 (d VARCHAR(16));
INSERT INTO t1 VALUES ("Monday"), ("Tuesday"), ("Wednesday"), ("Thursday"), ("Friday"), ("Saturday"), ("Sunday");
SELECT * FROM t1 WHERE d LIKE "T%";

SELECT * FROM t1 WHERE d LIKE "T%";
+----------+
| d        |
+----------+
| Tuesday  |
| Thursday |
+----------+

Select the days that contain the substring "es":

SELECT * FROM t1 WHERE d LIKE "%es%";

SELECT * FROM t1 WHERE d LIKE "%es%";
+-----------+
| d         |
+-----------+
| Tuesday   |
| Wednesday |
+-----------+

Select the six-character day names:

SELECT * FROM t1 WHERE d like "___day";

SELECT * FROM t1 WHERE d like "___day";
+---------+
| d       |
+---------+
| Monday  |
| Friday  |
| Sunday  |
+---------+

With the default collations, LIKE is case-insensitive:

SELECT * FROM t1 where d like "t%";

SELECT * FROM t1 where d like "t%";
+----------+
| d        |
+----------+
| Tuesday  |
| Thursday |
+----------+

Use COLLATE to specify a binary collation, forcing case-sensitive matches:

SELECT * FROM t1 WHERE d like "t%" COLLATE latin1_bin;

SELECT * FROM t1 WHERE d like "t%" COLLATE latin1_bin;
Empty set (0.00 sec)

You can include functions and operators in the expression to match. Select dates based on their day name:

CREATE TABLE t2 (d DATETIME);
INSERT INTO t2 VALUES
    ("2007-01-30 21:31:07"),
    ("1983-10-15 06:42:51"),
    ("2011-04-21 12:34:56"),
    ("2011-10-30 06:31:41"),
    ("2011-01-30 14:03:25"),
    ("2004-10-07 11:19:34");
SELECT * FROM t2 WHERE DAYNAME(d) LIKE "T%";

SELECT * FROM t2 WHERE DAYNAME(d) LIKE "T%";
+------------------+
| d                |
+------------------+
| 2007-01-30 21:31 |
| 2011-04-21 12:34 |
| 2004-10-07 11:19 |
+------------------+
3 rows in set, 7 warnings (0.00 sec)

Optimizing LIKE

  • MariaDB can use indexes for LIKE on string columns in the case where the LIKE doesn't start with % or _.
  • Starting from MariaDB 10.0, one can set the optimizer_use_condition_selectivity variable to 5. If this is done, then the optimizer will read optimizer_selectivity_sampling_limit rows to calculate the selectivity of the LIKE expression before starting to calculate the query plan. This can help speed up some LIKE queries by providing the optimizer with more information about your data.

See Also

1.2.2.27 LOAD_FILE

1.2.2.28 LOCATE

Syntax

LOCATE(substr,str), LOCATE(substr,str,pos)

Description

The first syntax returns the position of the first occurrence of substring substr in string str. The second syntax returns the position of the first occurrence of substring substr in string str, starting at position pos. Returns 0 if substr is not in str.

LOCATE() performs a case-insensitive search.

If any argument is NULL, returns NULL.

INSTR() is the same as the two-argument form of LOCATE(), except that the order of the arguments is reversed.

Examples

SELECT LOCATE('bar', 'foobarbar');
+----------------------------+
| LOCATE('bar', 'foobarbar') |
+----------------------------+
|                          4 |
+----------------------------+

SELECT LOCATE('My', 'Maria');
+-----------------------+
| LOCATE('My', 'Maria') |
+-----------------------+
|                     0 |
+-----------------------+

SELECT LOCATE('bar', 'foobarbar', 5);
+-------------------------------+
| LOCATE('bar', 'foobarbar', 5) |
+-------------------------------+
|                             7 |
+-------------------------------+

See Also

  • INSTR() ; Returns the position of a string withing a string
  • SUBSTRING_INDEX() ; Returns the substring from string before count occurrences of a delimiter

1.2.2.29 LOWER

Syntax

LOWER(str)

Contents

  1. Syntax
  2. Description
  3. Examples

Description

Returns the string str with all characters changed to lowercase according to the current character set mapping. The default is latin1 (cp1252 West European).

Examples

 SELECT LOWER('QUADRATICALLY');
+------------------------+
| LOWER('QUADRATICALLY') |
+------------------------+
| quadratically          |
+------------------------+

LOWER() (and UPPER()) are ineffective when applied to binary strings (BINARY, VARBINARY, BLOB). To perform lettercase conversion, CONVERT the string to a non-binary string:

SET @str = BINARY 'North Carolina';

SELECT LOWER(@str), LOWER(CONVERT(@str USING latin1));
+----------------+-----------------------------------+
| LOWER(@str)    | LOWER(CONVERT(@str USING latin1)) |
+----------------+-----------------------------------+
| North Carolina | north carolina                    |
+----------------+-----------------------------------+

1.2.2.30 LPAD

Syntax

LPAD(str, len [,padstr])

Contents

  1. Syntax
  2. Description
  3. Examples
  4. See Also

Description

Returns the string str, left-padded with the string padstr to a length of len characters. If str is longer than len, the return value is shortened to len characters. If padstr is omitted, the LPAD function pads spaces.

Prior to MariaDB 10.3.1, the padstr parameter was mandatory.

Returns NULL if given a NULL argument. If the result is empty (zero length), returns either an empty string or, from MariaDB 10.3.6 with SQL_MODE=Oracle, NULL.

The Oracle mode version of the function can be accessed outside of Oracle mode by using LPAD_ORACLE as the function name.

Examples

SELECT LPAD('hello',10,'.');
+----------------------+
| LPAD('hello',10,'.') |
+----------------------+
| .....hello           |
+----------------------+

SELECT LPAD('hello',2,'.');
+---------------------+
| LPAD('hello',2,'.') |
+---------------------+
| he                  |
+---------------------+

From MariaDB 10.3.1, with the pad string defaulting to space.

SELECT LPAD('hello',10);
+------------------+
| LPAD('hello',10) |
+------------------+
|      hello       |
+------------------+

Oracle mode version from MariaDB 10.3.6:

SELECT LPAD('',0),LPAD_ORACLE('',0);
+------------+-------------------+
| LPAD('',0) | LPAD_ORACLE('',0) |
+------------+-------------------+
|            | NULL              |
+------------+-------------------+

See Also

  • RPAD - Right-padding instead of left-padding.

1.2.2.31 LTRIM

Syntax

LTRIM(str)

Contents

  1. Syntax
  2. Description
  3. Examples
  4. See Also

Description

Returns the string str with leading space characters removed.

Returns NULL if given a NULL argument. If the result is empty, returns either an empty string, or, from MariaDB 10.3.6 with SQL_MODE=Oracle, NULL.

The Oracle mode version of the function can be accessed outside of Oracle mode by using LTRIM_ORACLE as the function name.

Examples

SELECT QUOTE(LTRIM('   MariaDB   '));
+-------------------------------+
| QUOTE(LTRIM('   MariaDB   ')) |
+-------------------------------+
| 'MariaDB   '                  |
+-------------------------------+

Oracle mode version from MariaDB 10.3.6:

SELECT LTRIM(''),LTRIM_ORACLE('');
+-----------+------------------+
| LTRIM('') | LTRIM_ORACLE('') |
+-----------+------------------+
|           | NULL             |
+-----------+------------------+

See Also

  • RTRIM - trailing spaces removed
  • TRIM - removes all given prefixes or suffixes

1.2.2.32 MAKE_SET

Syntax

MAKE_SET(bits,str1,str2,...)

Description

Returns a set value (a string containing substrings separated by "," characters) consisting of the strings that have the corresponding bit in bits set. str1 corresponds to bit 0, str2 to bit 1, and so on. NULL values in str1, str2, ... are not appended to the result.

Examples

SELECT MAKE_SET(1,'a','b','c');
+-------------------------+
| MAKE_SET(1,'a','b','c') |
+-------------------------+
| a                       |
+-------------------------+

SELECT MAKE_SET(1 | 4,'hello','nice','world');
+----------------------------------------+
| MAKE_SET(1 | 4,'hello','nice','world') |
+----------------------------------------+
| hello,world                            |
+----------------------------------------+

SELECT MAKE_SET(1 | 4,'hello','nice',NULL,'world');
+---------------------------------------------+
| MAKE_SET(1 | 4,'hello','nice',NULL,'world') |
+---------------------------------------------+
| hello                                       |
+---------------------------------------------+

SELECT QUOTE(MAKE_SET(0,'a','b','c'));
+--------------------------------+
| QUOTE(MAKE_SET(0,'a','b','c')) |
+--------------------------------+
| ''                             |
+--------------------------------+

1.2.2.33 MATCH AGAINST

Syntax

MATCH (col1,col2,...) AGAINST (expr [search_modifier])

Description

A special construct used to perform a fulltext search on a fulltext index.

See Fulltext Index Overview for a full description, and Full-text Indexes for more articles on the topic.

Examples

CREATE TABLE ft_myisam(copy TEXT,FULLTEXT(copy)) ENGINE=MyISAM;

INSERT INTO ft_myisam(copy) VALUES ('Once upon a time'), ('There was a wicked witch'), 
 ('Who ate everybody up');

SELECT * FROM ft_myisam WHERE MATCH(copy) AGAINST('wicked');
+--------------------------+
| copy                     |
+--------------------------+
| There was a wicked witch |
+--------------------------+

SELECT id, body, MATCH (title,body) AGAINST
    ('Security implications of running MySQL as root'
    IN NATURAL LANGUAGE MODE) AS score
    FROM articles WHERE MATCH (title,body) AGAINST
    ('Security implications of running MySQL as root'
    IN NATURAL LANGUAGE MODE);
+----+-------------------------------------+-----------------+
| id | body                                | score           |
+----+-------------------------------------+-----------------+
|  4 | 1. Never run mysqld as root. 2. ... | 1.5219271183014 |
|  6 | When configured properly, MySQL ... | 1.3114095926285 |
+----+-------------------------------------+-----------------+

1.2.2.34 Full-Text Index Stopwords

1.2.2.35 MID

Syntax

MID(str,pos,len)

Description

MID(str,pos,len) is a synonym for SUBSTRING(str,pos,len).

Examples

SELECT MID('abcd',4,1);
+-----------------+
| MID('abcd',4,1) |
+-----------------+
| d               |
+-----------------+

SELECT MID('abcd',2,2);
+-----------------+
| MID('abcd',2,2) |
+-----------------+
| bc              |
+-----------------+

A negative starting position:

SELECT MID('abcd',-2,4);
+------------------+
| MID('abcd',-2,4) |
+------------------+
| cd               |
+------------------+

1.2.2.36 NOT LIKE

Syntax

expr NOT LIKE pat [ESCAPE 'escape_char']

Description

This is the same as NOT (expr LIKE pat [ESCAPE 'escape_char']).

1.2.2.37 NOT REGEXP

1.2.2.38 OCTET_LENGTH

Syntax

OCTET_LENGTH(str)

Description

OCTET_LENGTH() returns the length of the given string, in octets (bytes). This is a synonym for LENGTHB(), and, when Oracle mode from MariaDB 10.3 is not set, a synonym for LENGTH().

A multi-byte character counts as multiple bytes. This means that for a string containing five two-byte characters, OCTET_LENGTH() returns 10, whereas CHAR_LENGTH() returns 5.

If str is not a string value, it is converted into a string. If str is NULL, the function returns NULL.

Examples

When Oracle mode from MariaDB 10.3 is not set:

SELECT CHAR_LENGTH('π'), LENGTH('π'), LENGTHB('π'), OCTET_LENGTH('π');
+-------------------+--------------+---------------+--------------------+
| CHAR_LENGTH('π')  | LENGTH('π')  | LENGTHB('π')  | OCTET_LENGTH('π')  |
+-------------------+--------------+---------------+--------------------+
|                 1 |            2 |             2 |                  2 |
+-------------------+--------------+---------------+--------------------+

In Oracle mode from MariaDB 10.3:

SELECT CHAR_LENGTH('π'), LENGTH('π'), LENGTHB('π'), OCTET_LENGTH('π');
+-------------------+--------------+---------------+--------------------+
| CHAR_LENGTH('π')  | LENGTH('π')  | LENGTHB('π')  | OCTET_LENGTH('π')  |
+-------------------+--------------+---------------+--------------------+
|                 1 |            1 |             2 |                  2 |
+-------------------+--------------+---------------+--------------------+

See Also

1.2.2.39 ORD

Syntax

ORD(str)

Description

If the leftmost character of the string str is a multi-byte character, returns the code for that character, calculated from the numeric values of its constituent bytes using this formula:

  (1st byte code)
+ (2nd byte code x 256)
+ (3rd byte code x 256 x 256) ...

If the leftmost character is not a multi-byte character, ORD() returns the same value as the ASCII() function.

Examples

SELECT ORD('2');
+----------+
| ORD('2') |
+----------+
|       50 |
+----------+

See Also

  • ASCII() - Return ASCII value of first character
  • CHAR() - Create a character from an integer value

1.2.2.40 POSITION

Syntax

POSITION(substr IN str)

Description

POSITION(substr IN str) is a synonym for LOCATE(substr,str).

It's part of ODBC 3.0.

1.2.2.41 QUOTE

Syntax

QUOTE(str)

Description

Quotes a string to produce a result that can be used as a properly escaped data value in an SQL statement. The string is returned enclosed by single quotes and with each instance of single quote ("'"), backslash ("\"), ASCII NUL, and Control-Z preceded by a backslash. If the argument is NULL, the return value is the word "NULL" without enclosing single quotes.

Examples

SELECT QUOTE("Don't!");
+-----------------+
| QUOTE("Don't!") |
+-----------------+
| 'Don\'t!'       |
+-----------------+

SELECT QUOTE(NULL); 
+-------------+
| QUOTE(NULL) |
+-------------+
| NULL        |
+-------------+

1.2.2.42 REPEAT Function

Syntax

REPEAT(str,count)

Description

Returns a string consisting of the string str repeated count times. If count is less than 1, returns an empty string. Returns NULL if str or count are NULL.

Examples

SELECT QUOTE(REPEAT('MariaDB ',4));
+------------------------------------+
| QUOTE(REPEAT('MariaDB ',4))        |
+------------------------------------+
| 'MariaDB MariaDB MariaDB MariaDB ' |
+------------------------------------+

1.2.2.43 REPLACE Function

Syntax

REPLACE(str,from_str,to_str)

Description

Returns the string str with all occurrences of the string from_str replaced by the string to_str. REPLACE() performs a case-sensitive match when searching for from_str.

Examples

SELECT REPLACE('www.mariadb.org', 'w', 'Ww');
+---------------------------------------+
| REPLACE('www.mariadb.org', 'w', 'Ww') |
+---------------------------------------+
| WwWwWw.mariadb.org                    |
+---------------------------------------+

1.2.2.44 REVERSE

Syntax

REVERSE(str)

Description

Returns the string str with the order of the characters reversed.

Examples

SELECT REVERSE('desserts');
+---------------------+
| REVERSE('desserts') |
+---------------------+
| stressed            |
+---------------------+

1.2.2.45 RIGHT

Syntax

RIGHT(str,len)

Description

Returns the rightmost len characters from the string str, or NULL if any argument is NULL.

Examples

SELECT RIGHT('MariaDB', 2);
+---------------------+
| RIGHT('MariaDB', 2) |
+---------------------+
| DB                  |
+---------------------+

1.2.2.46 RPAD

Syntax

RPAD(str, len [, padstr])

Contents

  1. Syntax
  2. Description
  3. Examples
  4. See Also

Description

Returns the string str, right-padded with the string padstr to a length of len characters. If str is longer than len, the return value is shortened to len characters. If padstr is omitted, the RPAD function pads spaces.

Prior to MariaDB 10.3.1, the padstr parameter was mandatory.

Returns NULL if given a NULL argument. If the result is empty (a length of zero), returns either an empty string, or, from MariaDB 10.3.6 with SQL_MODE=Oracle, NULL.

The Oracle mode version of the function can be accessed outside of Oracle mode by using RPAD_ORACLE as the function name.

Examples

SELECT RPAD('hello',10,'.');
+----------------------+
| RPAD('hello',10,'.') |
+----------------------+
| hello.....           |
+----------------------+

SELECT RPAD('hello',2,'.');
+---------------------+
| RPAD('hello',2,'.') |
+---------------------+
| he                  |
+---------------------+

From MariaDB 10.3.1, with the pad string defaulting to space.

SELECT RPAD('hello',30);
+--------------------------------+
| RPAD('hello',30)               |
+--------------------------------+
| hello                          |
+--------------------------------+

Oracle mode version from MariaDB 10.3.6:

SELECT RPAD('',0),RPAD_ORACLE('',0);
+------------+-------------------+
| RPAD('',0) | RPAD_ORACLE('',0) |
+------------+-------------------+
|            | NULL              |
+------------+-------------------+

See Also

  • LPAD - Left-padding instead of right-padding.

1.2.2.47 RTRIM

Syntax

RTRIM(str)

Contents

  1. Syntax
  2. Description
  3. Examples
  4. See Also

Description

Returns the string str with trailing space characters removed.

Returns NULL if given a NULL argument. If the result is empty, returns either an empty string, or, from MariaDB 10.3.6 with SQL_MODE=Oracle, NULL.

The Oracle mode version of the function can be accessed outside of Oracle mode by using RTRIM_ORACLE as the function name.

Examples

SELECT QUOTE(RTRIM('MariaDB    '));
+-----------------------------+
| QUOTE(RTRIM('MariaDB    ')) |
+-----------------------------+
| 'MariaDB'                   |
+-----------------------------+

Oracle mode version from MariaDB 10.3.6:

SELECT RTRIM(''),RTRIM_ORACLE('');
+-----------+------------------+
| RTRIM('') | RTRIM_ORACLE('') |
+-----------+------------------+
|           | NULL             |
+-----------+------------------+

See Also

  • LTRIM - leading spaces removed
  • TRIM - removes all given prefixes or suffixes

1.2.2.48 SFORMAT

MariaDB starting with 10.7.0

SFORMAT was added in MariaDB 10.7.0.

Description

The SFORMAT function takes an input string and a formatting specification and returns the string formatted using the rules the user passed in the specification.

It use the fmtlib library for Python-like (as well as Rust, C++20, etc) string formatting.

Only fmtlib 7.0.0+ is supported.

There is no native support for temporal and decimal values:

  • TIME_RESULT is handled as STRING_RESULT
  • DECIMAL_RESULT as REAL_RESULT

Examples

SELECT SFORMAT("The answer is {}.", 42);
+----------------------------------+
| SFORMAT("The answer is {}.", 42) |
+----------------------------------+
| The answer is 42.                |
+----------------------------------+

CREATE TABLE test_sformat(mdb_release char(6), mdev int, feature char(20));

INSERT INTO test_sformat VALUES('10.7.0', 25015, 'Python style sformat'), 
  ('10.7.0', 4958, 'UUID');

SELECT * FROM test_sformat;
+-------------+-------+----------------------+
| mdb_release | mdev  | feature              |
+-------------+-------+----------------------+
| 10.7.0      | 25015 | Python style sformat |
| 10.7.0      |  4958 | UUID                 |
+-------------+-------+----------------------+

SELECT SFORMAT('MariaDB Server {} has a preview for MDEV-{} which is about {}', 
  mdb_release, mdev, feature) AS 'Preview Release Examples'
  FROM test_sformat;
+----------------------------------------------------------------------------------------+
| Preview Release Examples                                                               |
+----------------------------------------------------------------------------------------+
| MariaDB Server 10.7.0 has a preview for MDEV-25015 which is about Python style sformat |
| MariaDB Server 10.7.0 has a preview for MDEV-4958 which is about UUID                  |
+----------------------------------------------------------------------------------------+

See Also

1.2.2.49 SOUNDEX

Syntax

SOUNDEX(str)

Description

Returns a soundex string from str. Two strings that sound almost the same should have identical soundex strings. A standard soundex string is four characters long, but the SOUNDEX() function returns an arbitrarily long string. You can use SUBSTRING() on the result to get a standard soundex string. All non-alphabetic characters in str are ignored. All international alphabetic characters outside the A-Z range are treated as vowels.

Important: When using SOUNDEX(), you should be aware of the following details:

  • This function, as currently implemented, is intended to work well with strings that are in the English language only. Strings in other languages may not produce reasonable results.
  • This function implements the original Soundex algorithm, not the more popular enhanced version (also described by D. Knuth). The difference is that original version discards vowels first and duplicates second, whereas the enhanced version discards duplicates first and vowels second.

Examples

SOUNDEX('Hello');
+------------------+
| SOUNDEX('Hello') |
+------------------+
| H400             |
+------------------+

SELECT SOUNDEX('MariaDB');
+--------------------+
| SOUNDEX('MariaDB') |
+--------------------+
| M631               |
+--------------------+

SELECT SOUNDEX('Knowledgebase');
+--------------------------+
| SOUNDEX('Knowledgebase') |
+--------------------------+
| K543212                  |
+--------------------------+

SELECT givenname, surname FROM users WHERE SOUNDEX(givenname) = SOUNDEX("robert");
+-----------+---------+
| givenname | surname |
+-----------+---------+
| Roberto   | Castro  |
+-----------+---------+

See Also

1.2.2.50 SOUNDS LIKE

Syntax

expr1 SOUNDS LIKE expr2

Description

This is the same as SOUNDEX(expr1) = SOUNDEX(expr2).

Example

SELECT givenname, surname FROM users WHERE givenname SOUNDS LIKE "robert";
+-----------+---------+
| givenname | surname |
+-----------+---------+
| Roberto   | Castro  |
+-----------+---------+

1.2.2.51 SPACE

Syntax

SPACE(N)

Description

Returns a string consisting of N space characters. If N is NULL, returns NULL.

Examples

SELECT QUOTE(SPACE(6));
+-----------------+
| QUOTE(SPACE(6)) |
+-----------------+
| '      '        |
+-----------------+

1.2.2.52 STRCMP

Syntax

STRCMP(expr1,expr2)

Description

STRCMP() returns 0 if the strings are the same, -1 if the first argument is smaller than the second according to the current sort order, and 1 if the strings are otherwise not the same. Returns NULL is either argument is NULL.

Examples

SELECT STRCMP('text', 'text2');
+-------------------------+
| STRCMP('text', 'text2') |
+-------------------------+
|                      -1 |
+-------------------------+

SELECT STRCMP('text2', 'text');
+-------------------------+
| STRCMP('text2', 'text') |
+-------------------------+
|                       1 |
+-------------------------+

SELECT STRCMP('text', 'text');
+------------------------+
| STRCMP('text', 'text') |
+------------------------+
|                      0 |
+------------------------+

1.2.2.53 SUBSTR

Description

SUBSTR() is a synonym for SUBSTRING().

1.2.2.54 SUBSTRING

Syntax

SUBSTRING(str,pos), 
SUBSTRING(str FROM pos), 
SUBSTRING(str,pos,len),
SUBSTRING(str FROM pos FOR len)

SUBSTR(str,pos), 
SUBSTR(str FROM pos), 
SUBSTR(str,pos,len),
SUBSTR(str FROM pos FOR len)

Contents

  1. Syntax
  2. Description
  3. Examples
  4. See Also

Description

The forms without a len argument return a substring from string str starting at position pos.

The forms with a len argument return a substring len characters long from string str, starting at position pos.

The forms that use FROM are standard SQL syntax.

It is also possible to use a negative value for pos. In this case, the beginning of the substring is pos characters from the end of the string, rather than the beginning. A negative value may be used for pos in any of the forms of this function.

By default, the position of the first character in the string from which the substring is to be extracted is reckoned as 1. For Oracle-compatibility, from MariaDB 10.3.3, when sql_mode is set to 'oracle', position zero is treated as position 1 (although the first character is still reckoned as 1).

If any argument is NULL, returns NULL.

Examples

SELECT SUBSTRING('Knowledgebase',5);
+------------------------------+
| SUBSTRING('Knowledgebase',5) |
+------------------------------+
| ledgebase                    |
+------------------------------+

SELECT SUBSTRING('MariaDB' FROM 6);
+-----------------------------+
| SUBSTRING('MariaDB' FROM 6) |
+-----------------------------+
| DB                          |
+-----------------------------+

SELECT SUBSTRING('Knowledgebase',3,7);
+--------------------------------+
| SUBSTRING('Knowledgebase',3,7) |
+--------------------------------+
| owledge                        |
+--------------------------------+

SELECT SUBSTRING('Knowledgebase', -4);
+--------------------------------+
| SUBSTRING('Knowledgebase', -4) |
+--------------------------------+
| base                           |
+--------------------------------+

SELECT SUBSTRING('Knowledgebase', -8, 4);
+-----------------------------------+
| SUBSTRING('Knowledgebase', -8, 4) |
+-----------------------------------+
| edge                              |
+-----------------------------------+

SELECT SUBSTRING('Knowledgebase' FROM -8 FOR 4);
+------------------------------------------+
| SUBSTRING('Knowledgebase' FROM -8 FOR 4) |
+------------------------------------------+
| edge                                     |
+------------------------------------------+

Oracle mode from MariaDB 10.3.3:

SELECT SUBSTR('abc',0,3);
+-------------------+
| SUBSTR('abc',0,3) |
+-------------------+
|                   |
+-------------------+

SELECT SUBSTR('abc',1,2);
+-------------------+
| SUBSTR('abc',1,2) |
+-------------------+
| ab                |
+-------------------+

SET sql_mode='oracle';

SELECT SUBSTR('abc',0,3);
+-------------------+
| SUBSTR('abc',0,3) |
+-------------------+
| abc               |
+-------------------+

SELECT SUBSTR('abc',1,2);
+-------------------+
| SUBSTR('abc',1,2) |
+-------------------+
| ab                |
+-------------------+

See Also

  • INSTR() - Returns the position of a string within a string
  • LOCATE() - Returns the position of a string within a string
  • SUBSTRING_INDEX() - Returns a string based on substring

1.2.2.55 SUBSTRING_INDEX

Syntax

SUBSTRING_INDEX(str,delim,count)

Contents

  1. Syntax
  2. Description
  3. Examples
  4. See Also

Description

Returns the substring from string str before count occurrences of the delimiter delim. If count is positive, everything to the left of the final delimiter (counting from the left) is returned. If count is negative, everything to the right of the final delimiter (counting from the right) is returned. SUBSTRING_INDEX() performs a case-sensitive match when searching for delim.

If any argument is NULL, returns NULL.

For example

SUBSTRING_INDEX('www.mariadb.org', '.', 2)

means "Return all of the characters up to the 2nd occurrence of ."

Examples

SELECT SUBSTRING_INDEX('www.mariadb.org', '.', 2);
+--------------------------------------------+
| SUBSTRING_INDEX('www.mariadb.org', '.', 2) |
+--------------------------------------------+
| www.mariadb                                |
+--------------------------------------------+

SELECT SUBSTRING_INDEX('www.mariadb.org', '.', -2);
+---------------------------------------------+
| SUBSTRING_INDEX('www.mariadb.org', '.', -2) |
+---------------------------------------------+
| mariadb.org                                 |
+---------------------------------------------+

See Also

  • INSTR() - Returns the position of a string within a string
  • LOCATE() - Returns the position of a string within a string
  • SUBSTRING() - Returns a string based on position

1.2.2.56 TO_BASE64

Syntax

TO_BASE64(str)

Description

Converts the string argument str to its base-64 encoded form, returning the result as a character string in the connection character set and collation.

The argument str will be converted to string first if it is not a string. A NULL argument will return a NULL result.

The reverse function, FROM_BASE64(), decodes an encoded base-64 string.

There are a numerous different methods to base-64 encode a string. The following are used by MariaDB and MySQL:

  • Alphabet value 64 is encoded as '+'.
  • Alphabet value 63 is encoded as '/'.
  • Encoding output is made up of groups of four printable characters, with each three bytes of data encoded using four characters. If the final group is not complete, it is padded with '=' characters to make up a length of four.
  • To divide long output, a newline is added after every 76 characters.
  • Decoding will recognize and ignore newlines, carriage returns, tabs, and spaces.

Examples

SELECT TO_BASE64('Maria');
+--------------------+
| TO_BASE64('Maria') |
+--------------------+
| TWFyaWE=           |
+--------------------+

1.2.2.57 TO_CHAR

MariaDB starting with 10.6.1

The TO_CHAR function was introduced in MariaDB 10.6.1 to enhance Oracle compatibility.

Syntax

TO_CHAR(expr[, fmt])

Contents

  1. Syntax
  2. Description
  3. Examples
  4. See Also

Description

The TO_CHAR function converts an expr of type date, datetime, time or timestamp to a string. The optional fmt argument supports YYYY/YYY/YY/RRRR/RR/MM/MON/MONTH/MI/DD/DY/HH/HH12/HH24/SS and special characters. The default value is "YYYY-MM-DD HH24:MI:SS".

In Oracle, TO_CHAR can also be used to convert numbers to strings, but this is not supported in MariaDB and will give an error.

Examples

SELECT TO_CHAR('1980-01-11 04:50:39', 'YYYY-MM-DD');
+----------------------------------------------+
| TO_CHAR('1980-01-11 04:50:39', 'YYYY-MM-DD') |
+----------------------------------------------+
| 1980-01-11                                   |
+----------------------------------------------+

SELECT TO_CHAR('1980-01-11 04:50:39', 'HH24-MI-SS');
+----------------------------------------------+
| TO_CHAR('1980-01-11 04:50:39', 'HH24-MI-SS') |
+----------------------------------------------+
| 04-50-39                                     |
+----------------------------------------------+

SELECT TO_CHAR('00-01-01 00:00:00', 'YY-MM-DD HH24:MI:SS');
+-----------------------------------------------------+
| TO_CHAR('00-01-01 00:00:00', 'YY-MM-DD HH24:MI:SS') |
+-----------------------------------------------------+
| 00-01-01 00:00:00                                   |
+-----------------------------------------------------+

SELECT TO_CHAR('99-12-31 23:59:59', 'YY-MM-DD HH24:MI:SS');
+-----------------------------------------------------+
| TO_CHAR('99-12-31 23:59:59', 'YY-MM-DD HH24:MI:SS') |
+-----------------------------------------------------+
| 99-12-31 23:59:59                                   |
+-----------------------------------------------------+

SELECT TO_CHAR('9999-12-31 23:59:59', 'YY-MM-DD HH24:MI:SS');
+-------------------------------------------------------+
| TO_CHAR('9999-12-31 23:59:59', 'YY-MM-DD HH24:MI:SS') |
+-------------------------------------------------------+
| 99-12-31 23:59:59                                     |
+-------------------------------------------------------+

SELECT TO_CHAR('21-01-03 08:30:00', 'Y-MONTH-DY HH:MI:SS');
+-----------------------------------------------------+
| TO_CHAR('21-01-03 08:30:00', 'Y-MONTH-DY HH:MI:SS') |
+-----------------------------------------------------+
| 1-January  -Sun 08:30:00                            |
+-----------------------------------------------------+

See Also

1.2.2.58 TRIM

Syntax

TRIM([{BOTH | LEADING | TRAILING} [remstr] FROM] str), TRIM([remstr FROM] str)

From MariaDB 10.3.6

TRIM_ORACLE([{BOTH | LEADING | TRAILING} [remstr] FROM] str), TRIM([remstr FROM] str)

Contents

  1. Syntax
  2. Description
  3. Examples
  4. See Also

Description

Returns the string str with all remstr prefixes or suffixes removed. If none of the specifiers BOTH, LEADING, or TRAILING is given, BOTH is assumed. remstr is optional and, if not specified, spaces are removed.

Returns NULL if given a NULL argument. If the result is empty, returns either an empty string, or, from MariaDB 10.3.6 with SQL_MODE=Oracle, NULL. SQL_MODE=Oracle is not set by default.

The Oracle mode version of the function can be accessed in any mode by using TRIM_ORACLE as the function name.

Examples

SELECT TRIM('  bar   ')\G
*************************** 1. row ***************************
TRIM('  bar   '): bar

SELECT TRIM(LEADING 'x' FROM 'xxxbarxxx')\G
*************************** 1. row ***************************
TRIM(LEADING 'x' FROM 'xxxbarxxx'): barxxx

SELECT TRIM(BOTH 'x' FROM 'xxxbarxxx')\G
*************************** 1. row ***************************
TRIM(BOTH 'x' FROM 'xxxbarxxx'): bar

SELECT TRIM(TRAILING 'xyz' FROM 'barxxyz')\G
*************************** 1. row ***************************
TRIM(TRAILING 'xyz' FROM 'barxxyz'): barx

From MariaDB 10.3.6, with SQL_MODE=Oracle not set:

SELECT TRIM(''),TRIM_ORACLE('');
+----------+-----------------+
| TRIM('') | TRIM_ORACLE('') |
+----------+-----------------+
|          | NULL            |
+----------+-----------------+

From MariaDB 10.3.6, with SQL_MODE=Oracle set:

SELECT TRIM(''),TRIM_ORACLE('');
+----------+-----------------+
| TRIM('') | TRIM_ORACLE('') |
+----------+-----------------+
| NULL     | NULL            |
+----------+-----------------+

See Also

  • LTRIM - leading spaces removed
  • RTRIM - trailing spaces removed

1.2.2.59 TRIM_ORACLE

MariaDB starting with 10.3.6

TRIM_ORACLE is a synonym for the Oracle mode version of the TRIM function, and is available in all modes.

1.2.2.60 UCASE

Syntax

UCASE(str)

Description

UCASE() is a synonym for UPPER().

1.2.2.61 UNCOMPRESS

Syntax

UNCOMPRESS(string_to_uncompress)

Description

Uncompresses a string compressed by the COMPRESS() function. If the argument is not a compressed value, the result is NULL. This function requires MariaDB to have been compiled with a compression library such as zlib. Otherwise, the return value is always NULL. The have_compress server system variable indicates whether a compression library is present.

Examples

SELECT UNCOMPRESS(COMPRESS('a string'));
+----------------------------------+
| UNCOMPRESS(COMPRESS('a string')) |
+----------------------------------+
| a string                         |
+----------------------------------+

SELECT UNCOMPRESS('a string');
+------------------------+
| UNCOMPRESS('a string') |
+------------------------+
| NULL                   |
+------------------------+

1.2.2.62 UNCOMPRESSED_LENGTH

Syntax

UNCOMPRESSED_LENGTH(compressed_string)

Description

Returns the length that the compressed string had before being compressed with COMPRESS().

UNCOMPRESSED_LENGTH() returns NULL or an incorrect result if the string is not compressed.

Until MariaDB 10.3.1, returns MYSQL_TYPE_LONGLONG, or bigint(10), in all cases. From MariaDB 10.3.1, returns MYSQL_TYPE_LONG, or int(10), when the result would fit within 32-bits.

Examples

SELECT UNCOMPRESSED_LENGTH(COMPRESS(REPEAT('a',30)));
+-----------------------------------------------+
| UNCOMPRESSED_LENGTH(COMPRESS(REPEAT('a',30))) |
+-----------------------------------------------+
|                                            30 |
+-----------------------------------------------+

1.2.2.63 UNHEX

Syntax

UNHEX(str)

Description

Performs the inverse operation of HEX(str). That is, it interprets each pair of hexadecimal digits in the argument as a number and converts it to the character represented by the number. The resulting characters are returned as a binary string.

If str is NULL, UNHEX() returns NULL.

Examples

SELECT HEX('MariaDB');
+----------------+
| HEX('MariaDB') |
+----------------+
| 4D617269614442 |
+----------------+

SELECT UNHEX('4D617269614442');
+-------------------------+
| UNHEX('4D617269614442') |
+-------------------------+
| MariaDB                 |
+-------------------------+

SELECT 0x4D617269614442;
+------------------+
| 0x4D617269614442 |
+------------------+
| MariaDB          |
+------------------+

SELECT UNHEX(HEX('string'));
+----------------------+
| UNHEX(HEX('string')) |
+----------------------+
| string               |
+----------------------+

SELECT HEX(UNHEX('1267'));
+--------------------+
| HEX(UNHEX('1267')) |
+--------------------+
| 1267               |
+--------------------+

See Also

1.2.2.64 UPDATEXML

Syntax

UpdateXML(xml_target, xpath_expr, new_xml)

Description

This function replaces a single portion of a given fragment of XML markup xml_target with a new XML fragment new_xml, and then returns the changed XML. The portion of xml_target that is replaced matches an XPath expression xpath_expr supplied by the user. If no expression matching xpath_expr is found, or if multiple matches are found, the function returns the original xml_target XML fragment. All three arguments should be strings.

Examples

SELECT
    UpdateXML('<a><b>ccc</b><d></d></a>', '/a', '<e>fff</e>') AS val1,
    UpdateXML('<a><b>ccc</b><d></d></a>', '/b', '<e>fff</e>') AS val2,
    UpdateXML('<a><b>ccc</b><d></d></a>', '//b', '<e>fff</e>') AS val3,
    UpdateXML('<a><b>ccc</b><d></d></a>', '/a/d', '<e>fff</e>') AS val4,
    UpdateXML('<a><d></d><b>ccc</b><d></d></a>', '/a/d', '<e>fff</e>') AS val5
    \G
*************************** 1. row ***************************
val1: <e>fff</e>
val2: <a><b>ccc</b><d></d></a>
val3: <a><e>fff</e><d></d></a>
val4: <a><b>ccc</b><e>fff</e></a>
val5: <a><d></d><b>ccc</b><d></d></a>
1 row in set (0.00 sec)

1.2.2.65 UPPER

Syntax

UPPER(str)

Description

Returns the string str with all characters changed to uppercase according to the current character set mapping. The default is latin1 (cp1252 West European).

SELECT UPPER(surname), givenname FROM users ORDER BY surname;
+----------------+------------+
| UPPER(surname) | givenname  |
+----------------+------------+
| ABEL           | Jacinto    |
| CASTRO         | Robert     |
| COSTA          | Phestos    |
| MOSCHELLA      | Hippolytos |
+----------------+------------+

UPPER() is ineffective when applied to binary strings (BINARY, VARBINARY, BLOB). The description of LOWER() shows how to perform lettercase conversion of binary strings.

1.2.2.66 WEIGHT_STRING

Syntax

WEIGHT_STRING(str [AS {CHAR|BINARY}(N)] [LEVEL levels] [flags])
  levels: N [ASC|DESC|REVERSE] [, N [ASC|DESC|REVERSE]] ...

Description

Returns a binary string representing the string's sorting and comparison value. A string with a lower result means that for sorting purposes the string appears before a string with a higher result.

WEIGHT_STRING() is particularly useful when adding new collations, for testing purposes.

If str is a non-binary string (CHAR, VARCHAR or TEXT), WEIGHT_STRING returns the string's collation weight. If str is a binary string (BINARY, VARBINARY or BLOB), the return value is simply the input value, since the weight for each byte in a binary string is the byte value.

WEIGHT_STRING() returns NULL if given a NULL input.

The optional AS clause permits casting the input string to a binary or non-binary string, as well as to a particular length.

AS BINARY(N) measures the length in bytes rather than characters, and right pads with 0x00 bytes to the desired length.

AS CHAR(N) measures the length in characters, and right pads with spaces to the desired length.

N has a minimum value of 1, and if it is less than the length of the input string, the string is truncated without warning.

The optional LEVEL clause specifies that the return value should contain weights for specific collation levels. The levels specifier can either be a single integer, a comma-separated list of integers, or a range of integers separated by a dash (whitespace is ignored). Integers can range from 1 to a maximum of 6, dependent on the collation, and need to be listed in ascending order.

If the LEVEL clause is no provided, a default of 1 to the maximum for the collation is assumed.

If the LEVEL is specified without using a range, an optional modifier is permitted.

ASC, the default, returns the weights without any modification.

DESC returns bitwise-inverted weights.

REVERSE returns the weights in reverse order.

Examples

The examples below use the HEX() function to represent non-printable results in hexadecimal format.

SELECT HEX(WEIGHT_STRING('x'));
+-------------------------+
| HEX(WEIGHT_STRING('x')) |
+-------------------------+
| 0058                    |
+-------------------------+

SELECT HEX(WEIGHT_STRING('x' AS BINARY(4)));
+--------------------------------------+
| HEX(WEIGHT_STRING('x' AS BINARY(4))) |
+--------------------------------------+
| 78000000                             |
+--------------------------------------+

SELECT HEX(WEIGHT_STRING('x' AS CHAR(4)));
+------------------------------------+
| HEX(WEIGHT_STRING('x' AS CHAR(4))) |
+------------------------------------+
| 0058002000200020                   |
+------------------------------------+

SELECT HEX(WEIGHT_STRING(0xaa22ee LEVEL 1));
+--------------------------------------+
| HEX(WEIGHT_STRING(0xaa22ee LEVEL 1)) |
+--------------------------------------+
| AA22EE                               |
+--------------------------------------+

SELECT HEX(WEIGHT_STRING(0xaa22ee LEVEL 1 DESC));
+-------------------------------------------+
| HEX(WEIGHT_STRING(0xaa22ee LEVEL 1 DESC)) |
+-------------------------------------------+
| 55DD11                                    |
+-------------------------------------------+

SELECT HEX(WEIGHT_STRING(0xaa22ee LEVEL 1 REVERSE));
+----------------------------------------------+
| HEX(WEIGHT_STRING(0xaa22ee LEVEL 1 REVERSE)) |
+----------------------------------------------+
| EE22AA                                       |
+----------------------------------------------+

1.2.2.67 Type Conversion

Contents

  1. Rules for Conversion on Comparison
    1. Comparison Examples
  2. Rules for Conversion on Dyadic Arithmetic Operations
    1. Arithmetic Examples

Implicit type conversion takes place when MariaDB is using operands or different types, in order to make the operands compatible.

It is best practice not to rely upon implicit conversion; rather use CAST to explicitly convert types.

Rules for Conversion on Comparison

  • If either argument is NULL, the result of the comparison is NULL unless the NULL-safe <=> equality comparison operator is used.
  • If both arguments are integers, they are compared as integers.
  • If both arguments are strings, they are compared as strings.
  • If one argument is decimal and the other argument is decimal or integer, they are compared as decimals.
  • If one argument is decimal and the other argument is a floating point, they are compared as floating point values.
  • If a hexadecimal argument is not compared to a number, it is treated as a binary string.
  • If a constant is compared to a TIMESTAMP or DATETIME, the constant is converted to a timestamp, unless used as an argument to the IN function.
  • In other cases, arguments are compared as floating point, or real, numbers.

Note that if a string column is being compared with a numeric value, MariaDB will not use the index on the column, as there are numerous alternatives that may evaluate as equal (see examples below).

Comparison Examples

Converting a string to a number:

SELECT 15+'15';
+---------+
| 15+'15' |
+---------+
|      30 |
+---------+

Converting a number to a string:

SELECT CONCAT(15,'15');
+-----------------+
| CONCAT(15,'15') |
+-----------------+
| 1515            |
+-----------------+

Floating point number errors:

SELECT '9746718491924563214' = 9746718491924563213;
+---------------------------------------------+
| '9746718491924563214' = 9746718491924563213 |
+---------------------------------------------+
|                                           1 |
+---------------------------------------------+

Numeric equivalence with strings:

SELECT '5' = 5;
+---------+
| '5' = 5 |
+---------+
|       1 |
+---------+

SELECT '   5' = 5;
+------------+
| '   5' = 5 |
+------------+
|          1 |
+------------+

SELECT '   5  ' = 5;
+--------------+
| '   5  ' = 5 |
+--------------+
|            1 |
+--------------+
1 row in set, 1 warning (0.000 sec)

SHOW WARNINGS;
+-------+------+--------------------------------------------+
| Level | Code | Message                                    |
+-------+------+--------------------------------------------+
| Note  | 1292 | Truncated incorrect DOUBLE value: '   5  ' |
+-------+------+--------------------------------------------+

As a result of the above, MariaDB cannot use the index when comparing a string with a numeric value in the example below:

CREATE TABLE t (a VARCHAR(10), b VARCHAR(10), INDEX idx_a (a));

INSERT INTO t VALUES ('1', '1'), ('2', '2'), ('3', '3'), ('4', '4'), ('5', '5'), ('1', '5');

EXPLAIN SELECT * FROM t WHERE a = '3' \G
*************************** 1. row ***************************
           id: 1
  select_type: SIMPLE
        table: t
         type: ref
possible_keys: idx_a
          key: idx_a
      key_len: 13
          ref: const
         rows: 1
        Extra: Using index condition

EXPLAIN SELECT * FROM t WHERE a = 3 \G
*************************** 1. row ***************************
           id: 1
  select_type: SIMPLE
        table: t
         type: ALL
possible_keys: idx_a
          key: NULL
      key_len: NULL
          ref: NULL
         rows: 6
        Extra: Using where

Rules for Conversion on Dyadic Arithmetic Operations

Implicit type conversion also takes place on dyadic arithmetic operations (+,-,*,/). MariaDB chooses the minimum data type that is guaranteed to fit the result and converts both arguments to the result data type.

For addition (+), subtraction (-) and multiplication (*), the result data type is chosen as follows:

  • If either of the arguments is an approximate number (float, double), the result is double.
  • If either of the arguments is a string (char, varchar, text), the result is double.
  • If either of the arguments is a decimal number, the result is decimal.
  • If either of the arguments is of a temporal type with a non-zero fractional second precision (time(N), datetime(N), timestamp(N)), the result is decimal.
  • If either of the arguments is of a temporal type with a zero fractional second precision (time(0), date, datetime(0), timestamp(0)), the result may vary between int, int unsigned, bigint or bigint unsigned, depending on the exact data type combination.
  • If both arguments are integer numbers (tinyint, smallint, mediumint, bigint), the result may vary between int, int unsigned, bigint or bigint unsigned, depending of the exact data types and their signs.

For division (/), the result data type is chosen as follows:

  • If either of the arguments is an approximate number (float, double), the result is double.
  • If either of the arguments is a string (char, varchar, text), the result is double.
  • Otherwise, the result is decimal.

Arithmetic Examples

Note, the above rules mean that when an argument of a temporal data type appears in addition or subtraction, it's treated as a number by default.

SELECT TIME'10:20:30' + 1;
+--------------------+
| TIME'10:20:30' + 1 |
+--------------------+
|             102031 |
+--------------------+

In order to do temporal addition or subtraction instead, use the DATE_ADD() or DATE_SUB() functions, or an INTERVAL expression as the second argument:

SELECT TIME'10:20:30' + INTERVAL 1 SECOND;
+------------------------------------+
| TIME'10:20:30' + INTERVAL 1 SECOND |
+------------------------------------+
| 10:20:31                           |
+------------------------------------+

SELECT "2.2" + 3;
+-----------+
| "2.2" + 3 |
+-----------+
|       5.2 |
+-----------+

SELECT 2.2 + 3;
+---------+
| 2.2 + 3 |
+---------+
| 5.2     |
+---------+

SELECT 2.2 / 3;
+---------+
| 2.2 / 3 |
+---------+
| 0.73333 |
+---------+

SELECT "2.2" / 3;
+--------------------+
| "2.2" / 3          |
+--------------------+
| 0.7333333333333334 |
+--------------------+

1.2.3 Date & Time Functions

Functions for handling date and time, e.g. TIME, DATE, DAYNAME etc.

There are 3 related questions.

1.2.3.1 Microseconds in MariaDB

Contents

  1. Additional Information
  2. MySQL 5.6 Microseconds
  3. See Also

The TIME, DATETIME, and TIMESTAMP types, along with the temporal functions, CAST and dynamic columns, support microseconds. The datetime precision of a column can be specified when creating the table with CREATE TABLE, for example:

CREATE TABLE example(
  col_microsec DATETIME(6),
  col_millisec TIME(3)
);

Generally, the precision can be specified for any TIME, DATETIME, or TIMESTAMP column, in parentheses, after the type name. The datetime precision specifies number of digits after the decimal dot and can be any integer number from 0 to 6. If no precision is specified it is assumed to be 0, for backward compatibility reasons.

A datetime precision can be specified wherever a type name is used. For example:

  • when declaring arguments of stored routines.
  • when specifying a return type of a stored function.
  • when declaring variables.
  • in a CAST function:
    create function example(x datetime(5)) returns time(4)
begin
  declare y timestamp(6);
  return cast(x as time(2));
end;

%f is used as the formatting option for microseconds in the STR_TO_DATE, DATE_FORMAT and FROM_UNIXTIME functions, for example:

SELECT STR_TO_DATE('20200809 020917076','%Y%m%d %H%i%s%f');
+-----------------------------------------------------+
| STR_TO_DATE('20200809 020917076','%Y%m%d %H%i%s%f') |
+-----------------------------------------------------+
| 2020-08-09 02:09:17.076000                          |
+-----------------------------------------------------+

Additional Information

  • when comparing anything to a temporal value (DATETIME, TIME, DATE, or TIMESTAMP), both values are compared as temporal values, not as strings.
  • The INFORMATION_SCHEMA.COLUMNS table has a new column DATETIME_PRECISION
  • NOW(), CURTIME(), UTC_TIMESTAMP(), UTC_TIME(), CURRENT_TIME(), CURRENT_TIMESTAMP(), LOCALTIME() and LOCALTIMESTAMP() now accept datetime precision as an optional argument. For example:
    SELECT CURTIME(4);
--> 10:11:12.3456
  • TIME_TO_SEC() and UNIX_TIMESTAMP() preserve microseconds of the argument. These functions will return a decimal number if the result non-zero datetime precision and an integer otherwise (for backward compatibility).
    SELECT TIME_TO_SEC('10:10:10.12345');
--> 36610.12345
  • Current versions of this patch fix a bug in the following optimization: in certain queries with DISTINCT MariaDB can ignore this clause if it can prove that all result rows are unique anyway, for example, when a primary key is compared with a constant. Sometimes this optimization was applied incorrectly, though — for example, when comparing a string with a date constant. This is now fixed.
  • DATE_ADD() and DATE_SUB() functions can now take a TIME expression as an argument (not just DATETIME as before).
    SELECT TIME('10:10:10') + INTERVAL 100 MICROSECOND;
--> 10:10:10.000100
  • The event_time field in the mysql.general_log table and the start_time, query_time, and lock_time fields in the mysql.slow_log table now store values with microsecond precision.
  • This patch fixed a bug when comparing a temporal value using the BETWEEN operator and one of the operands is NULL.
  • The old syntax TIMESTAMP(N), where N is the display width, is no longer supported. It was deprecated in MySQL 4.1.0 (released on 2003-04-03).
  • when a DATETIME value is compared to a TIME value, the latter is treated as a full datetime with a zero date part, similar to comparing DATE to a DATETIME, or to comparing DECIMAL numbers. Earlier versions of MariaDB used to compare only the time part of both operands in such a case.
  • In MariaDB, an extra column TIME_MS has been added to the INFORMATION_SCHEMA.PROCESSLIST table, as well as to the output of SHOW FULL PROCESSLIST.

Note: When you convert a temporal value to a value with a smaller precision, it will be truncated, not rounded. This is done to guarantee that the date part is not changed. For example:

SELECT CAST('2009-12-31 23:59:59.998877' as DATETIME(3));
-> 2009-12-31 23:59:59.998

MySQL 5.6 Microseconds

MySQL 5.6 introduced microseconds using a slightly different implementation to MariaDB 5.3. Since MariaDB 10.1, MariaDB has defaulted to the MySQL format, by means of the --mysql56-temporal-format variable. The MySQL version requires slightly more storage but has some advantages in permitting the eventual support of negative dates, and in replication.

See Also

1.2.3.2 Date and Time Units

The INTERVAL keyword can be used to add or subtract a time interval of time to a DATETIME, DATE or TIME value.

The syntax is:

INTERVAL time_quantity time_unit

For example, the SECOND unit is used below by the DATE_ADD() function:

SELECT '2008-12-31 23:59:59' + INTERVAL 1 SECOND;
+-------------------------------------------+
| '2008-12-31 23:59:59' + INTERVAL 1 SECOND |
+-------------------------------------------+
| 2009-01-01 00:00:00                       |
+-------------------------------------------+

The following units are valid:

UnitDescription
MICROSECONDMicroseconds
SECONDSeconds
MINUTEMinutes
HOURHours
DAYDays
WEEKWeeks
MONTHMonths
QUARTERQuarters
YEARYears
SECOND_MICROSECONDSeconds.Microseconds
MINUTE_MICROSECONDMinutes.Seconds.Microseconds
MINUTE_SECONDMinutes.Seconds
HOUR_MICROSECONDHours.Minutes.Seconds.Microseconds
HOUR_SECONDHours.Minutes.Seconds
HOUR_MINUTEHours.Minutes
DAY_MICROSECONDDays Hours.Minutes.Seconds.Microseconds
DAY_SECONDDays Hours.Minutes.Seconds
DAY_MINUTEDays Hours.Minutes
DAY_HOURDays Hours
YEAR_MONTHYears-Months

The time units containing an underscore are composite; that is, they consist of multiple base time units. For base time units, time_quantity is an integer number. For composite units, the quantity must be expressed as a string with multiple integer numbers separated by any punctuation character.

Example of composite units:

INTERVAL '2:2' YEAR_MONTH
INTERVAL '1:30:30' HOUR_SECOND
INTERVAL '1!30!30' HOUR_SECOND -- same as above

Time units can be used in the following contexts:

See also

1.2.3.3 ADD_MONTHS

MariaDB starting with 10.6.1

The ADD_MONTHS function was introduced in MariaDB 10.6.1 to enhance Oracle compatibility. Similar functionality can be achieved with the DATE_ADD function.

Syntax

ADD_MONTHS(date, months)

Contents

  1. Syntax
  2. Description
  3. Examples
  4. See Also

Description

ADD_MONTHS adds an integer months to a given date (DATE, DATETIME or TIMESTAMP), returning the resulting date.

months can be positive or negative.

The resulting day component will remain the same as that specified in date, unless the resulting month has fewer days than the day component of the given date, in which case the day will be the last day of the resulting month.

Returns NULL if given an invalid date, or a NULL argument.

Examples

SELECT ADD_MONTHS('2012-01-31', 2);
+-----------------------------+
| ADD_MONTHS('2012-01-31', 2) |
+-----------------------------+
| 2012-03-31                  |
+-----------------------------+

SELECT ADD_MONTHS('2012-01-31', -5);
+------------------------------+
| ADD_MONTHS('2012-01-31', -5) |
+------------------------------+
| 2011-08-31                   |
+------------------------------+

SELECT ADD_MONTHS('2011-01-31', 1);
+-----------------------------+
| ADD_MONTHS('2011-01-31', 1) |
+-----------------------------+
| 2011-02-28                  |
+-----------------------------+

SELECT ADD_MONTHS('2012-01-31', 1);
+-----------------------------+
| ADD_MONTHS('2012-01-31', 1) |
+-----------------------------+
| 2012-02-29                  |
+-----------------------------+

SELECT ADD_MONTHS('2012-01-31', 2);
+-----------------------------+
| ADD_MONTHS('2012-01-31', 2) |
+-----------------------------+
| 2012-03-31                  |
+-----------------------------+

SELECT ADD_MONTHS('2012-01-31', 3);
+-----------------------------+
| ADD_MONTHS('2012-01-31', 3) |
+-----------------------------+
| 2012-04-30                  |
+-----------------------------+

See Also

1.2.3.4 ADDDATE

Syntax

ADDDATE(date,INTERVAL expr unit), ADDDATE(expr,days)

Description

When invoked with the INTERVAL form of the second argument, ADDDATE() is a synonym for DATE_ADD(). The related function SUBDATE() is a synonym for DATE_SUB(). For information on the INTERVAL unit argument, see the discussion for DATE_ADD().

When invoked with the days form of the second argument, MariaDB treats it as an integer number of days to be added to expr.

Examples

SELECT DATE_ADD('2008-01-02', INTERVAL 31 DAY);
+-----------------------------------------+
| DATE_ADD('2008-01-02', INTERVAL 31 DAY) |
+-----------------------------------------+
| 2008-02-02                              |
+-----------------------------------------+

SELECT ADDDATE('2008-01-02', INTERVAL 31 DAY);
+----------------------------------------+
| ADDDATE('2008-01-02', INTERVAL 31 DAY) |
+----------------------------------------+
| 2008-02-02                             |
+----------------------------------------+

SELECT ADDDATE('2008-01-02', 31);
+---------------------------+
| ADDDATE('2008-01-02', 31) |
+---------------------------+
| 2008-02-02                |
+---------------------------+

CREATE TABLE t1 (d DATETIME);
INSERT INTO t1 VALUES
    ("2007-01-30 21:31:07"),
    ("1983-10-15 06:42:51"),
    ("2011-04-21 12:34:56"),
    ("2011-10-30 06:31:41"),
    ("2011-01-30 14:03:25"),
    ("2004-10-07 11:19:34");

SELECT d, ADDDATE(d, 10) from t1;
+---------------------+---------------------+
| d                   | ADDDATE(d, 10)      |
+---------------------+---------------------+
| 2007-01-30 21:31:07 | 2007-02-09 21:31:07 |
| 1983-10-15 06:42:51 | 1983-10-25 06:42:51 |
| 2011-04-21 12:34:56 | 2011-05-01 12:34:56 |
| 2011-10-30 06:31:41 | 2011-11-09 06:31:41 |
| 2011-01-30 14:03:25 | 2011-02-09 14:03:25 |
| 2004-10-07 11:19:34 | 2004-10-17 11:19:34 |
+---------------------+---------------------+

SELECT d, ADDDATE(d, INTERVAL 10 HOUR) from t1;
+---------------------+------------------------------+
| d                   | ADDDATE(d, INTERVAL 10 HOUR) |
+---------------------+------------------------------+
| 2007-01-30 21:31:07 | 2007-01-31 07:31:07          |
| 1983-10-15 06:42:51 | 1983-10-15 16:42:51          |
| 2011-04-21 12:34:56 | 2011-04-21 22:34:56          |
| 2011-10-30 06:31:41 | 2011-10-30 16:31:41          |
| 2011-01-30 14:03:25 | 2011-01-31 00:03:25          |
| 2004-10-07 11:19:34 | 2004-10-07 21:19:34          |
+---------------------+------------------------------+

1.2.3.5 ADDTIME

Syntax

ADDTIME(expr1,expr2)

Description

ADDTIME() adds expr2 to expr1 and returns the result. expr1 is a time or datetime expression, and expr2 is a time expression.

Examples

SELECT ADDTIME('2007-12-31 23:59:59.999999', '1 1:1:1.000002');
+---------------------------------------------------------+
| ADDTIME('2007-12-31 23:59:59.999999', '1 1:1:1.000002') |
+---------------------------------------------------------+
| 2008-01-02 01:01:01.000001                              |
+---------------------------------------------------------+

SELECT ADDTIME('01:00:00.999999', '02:00:00.999998');
+-----------------------------------------------+
| ADDTIME('01:00:00.999999', '02:00:00.999998') |
+-----------------------------------------------+
| 03:00:01.999997                               |
+-----------------------------------------------+

1.2.3.6 CONVERT_TZ

Syntax

CONVERT_TZ(dt,from_tz,to_tz)

Description

CONVERT_TZ() converts a datetime value dt from the time zone given by from_tz to the time zone given by to_tz and returns the resulting value.

In order to use named time zones, such as GMT, MET or Africa/Johannesburg, the time_zone tables must be loaded (see mysql_tzinfo_to_sql).

No conversion will take place if the value falls outside of the supported TIMESTAMP range ('1970-01-01 00:00:01' to '2038-01-19 05:14:07' UTC) when converted from from_tz to UTC.

This function returns NULL if the arguments are invalid (or named time zones have not been loaded).

See time zones for more information.

Examples

SELECT CONVERT_TZ('2016-01-01 12:00:00','+00:00','+10:00');
+-----------------------------------------------------+
| CONVERT_TZ('2016-01-01 12:00:00','+00:00','+10:00') |
+-----------------------------------------------------+
| 2016-01-01 22:00:00                                 |
+-----------------------------------------------------+

Using named time zones (with the time zone tables loaded):

SELECT CONVERT_TZ('2016-01-01 12:00:00','GMT','Africa/Johannesburg');
+---------------------------------------------------------------+
| CONVERT_TZ('2016-01-01 12:00:00','GMT','Africa/Johannesburg') |
+---------------------------------------------------------------+
| 2016-01-01 14:00:00                                           |
+---------------------------------------------------------------+

The value is out of the TIMESTAMP range, so no conversion takes place:

SELECT CONVERT_TZ('1969-12-31 22:00:00','+00:00','+10:00');
+-----------------------------------------------------+
| CONVERT_TZ('1969-12-31 22:00:00','+00:00','+10:00') |
+-----------------------------------------------------+
| 1969-12-31 22:00:00                                 |
+-----------------------------------------------------+

1.2.3.7 CURDATE

Syntax

CURDATE()
CURRENT_DATE
CURRENT_DATE()

Description

CURDATE returns the current date as a value in 'YYYY-MM-DD' or YYYYMMDD format, depending on whether the function is used in a string or numeric context.

CURRENT_DATE and CURRENT_DATE() are synonyms.

Examples

SELECT CURDATE();
+------------+
| CURDATE()  |
+------------+
| 2019-03-05 |
+------------+

In a numeric context (note this is not performing date calculations):

SELECT CURDATE() +0;
+--------------+
| CURDATE() +0 |
+--------------+
|     20190305 |
+--------------+

Data calculation:

SELECT CURDATE() - INTERVAL 5 DAY;
+----------------------------+
| CURDATE() - INTERVAL 5 DAY |
+----------------------------+
| 2019-02-28                 |
+----------------------------+

1.2.3.8 CURRENT_DATE

Syntax

CURRENT_DATE, CURRENT_DATE()

Description

CURRENT_DATE and CURRENT_DATE() are synonyms for CURDATE().

1.2.3.9 CURRENT_TIME

Syntax

CURRENT_TIME
CURRENT_TIME([precision])

Description

CURRENT_TIME and CURRENT_TIME() are synonyms for CURTIME().

See Also

1.2.3.10 CURRENT_TIMESTAMP

Syntax

CURRENT_TIMESTAMP
CURRENT_TIMESTAMP([precision])

Description

CURRENT_TIMESTAMP and CURRENT_TIMESTAMP() are synonyms for NOW().

See Also

1.2.3.11 CURTIME

Syntax

CURTIME([precision])

Description

Returns the current time as a value in 'HH:MM:SS' or HHMMSS.uuuuuu format, depending on whether the function is used in a string or numeric context. The value is expressed in the current time zone.

The optional precision determines the microsecond precision. See Microseconds in MariaDB.

Examples

SELECT CURTIME();
+-----------+
| CURTIME() |
+-----------+
| 12:45:39  |
+-----------+

SELECT CURTIME() + 0;
+---------------+
| CURTIME() + 0 |
+---------------+
| 124545.000000 |
+---------------+

With precision:

SELECT CURTIME(2);
+-------------+
| CURTIME(2)  |
+-------------+
| 09:49:08.09 |
+-------------+

See Also

1.2.3.12 DATE FUNCTION

Syntax

DATE(expr)

Description

Extracts the date part of the date or datetime expression expr.

Examples

SELECT DATE('2013-07-18 12:21:32');
+-----------------------------+
| DATE('2013-07-18 12:21:32') |
+-----------------------------+
| 2013-07-18                  |
+-----------------------------+

Error Handling

Until MariaDB 5.5.32, some versions of MariaDB returned 0000-00-00 when passed an invalid date. From 5.5.32, NULL is returned.

1.2.3.13 DATEDIFF

Syntax

DATEDIFF(expr1,expr2)

Description

DATEDIFF() returns (expr1 – expr2) expressed as a value in days from one date to the other. expr1 and expr2 are date or date-and-time expressions. Only the date parts of the values are used in the calculation.

Examples

SELECT DATEDIFF('2007-12-31 23:59:59','2007-12-30');
+----------------------------------------------+
| DATEDIFF('2007-12-31 23:59:59','2007-12-30') |
+----------------------------------------------+
|                                            1 |
+----------------------------------------------+

SELECT DATEDIFF('2010-11-30 23:59:59','2010-12-31');
+----------------------------------------------+
| DATEDIFF('2010-11-30 23:59:59','2010-12-31') |
+----------------------------------------------+
|                                          -31 |
+----------------------------------------------+

CREATE TABLE t1 (d DATETIME);
INSERT INTO t1 VALUES
    ("2007-01-30 21:31:07"),
    ("1983-10-15 06:42:51"),
    ("2011-04-21 12:34:56"),
    ("2011-10-30 06:31:41"),
    ("2011-01-30 14:03:25"),
    ("2004-10-07 11:19:34");

SELECT NOW();
+---------------------+
| NOW()               |
+---------------------+
| 2011-05-23 10:56:05 |
+---------------------+

SELECT d, DATEDIFF(NOW(),d) FROM t1;
+---------------------+-------------------+
| d                   | DATEDIFF(NOW(),d) |
+---------------------+-------------------+
| 2007-01-30 21:31:07 |              1574 |
| 1983-10-15 06:42:51 |             10082 |
| 2011-04-21 12:34:56 |                32 |
| 2011-10-30 06:31:41 |              -160 |
| 2011-01-30 14:03:25 |               113 |
| 2004-10-07 11:19:34 |              2419 |
+---------------------+-------------------+

1.2.3.14 DATE_ADD

Syntax

DATE_ADD(date,INTERVAL expr unit)

Contents

  1. Syntax
  2. Description
  3. Examples
  4. See Also

Description

Performs date arithmetic. The date argument specifies the starting date or datetime value. expr is an expression specifying the interval value to be added or subtracted from the starting date. expr is a string; it may start with a "-" for negative intervals. unit is a keyword indicating the units in which the expression should be interpreted. See Date and Time Units for a complete list of permitted units.

Examples

SELECT '2008-12-31 23:59:59' + INTERVAL 1 SECOND;
+-------------------------------------------+
| '2008-12-31 23:59:59' + INTERVAL 1 SECOND |
+-------------------------------------------+
| 2009-01-01 00:00:00                       |
+-------------------------------------------+

SELECT INTERVAL 1 DAY + '2008-12-31';
+-------------------------------+
| INTERVAL 1 DAY + '2008-12-31' |
+-------------------------------+
| 2009-01-01                    |
+-------------------------------+

SELECT '2005-01-01' - INTERVAL 1 SECOND;
+----------------------------------+
| '2005-01-01' - INTERVAL 1 SECOND |
+----------------------------------+
| 2004-12-31 23:59:59              |
+----------------------------------+

SELECT DATE_ADD('2000-12-31 23:59:59', INTERVAL 1 SECOND);
+----------------------------------------------------+
| DATE_ADD('2000-12-31 23:59:59', INTERVAL 1 SECOND) |
+----------------------------------------------------+
| 2001-01-01 00:00:00                                |
+----------------------------------------------------+

SELECT DATE_ADD('2010-12-31 23:59:59', INTERVAL 1 DAY);
+-------------------------------------------------+
| DATE_ADD('2010-12-31 23:59:59', INTERVAL 1 DAY) |
+-------------------------------------------------+
| 2011-01-01 23:59:59                             |
+-------------------------------------------------+

SELECT DATE_ADD('2100-12-31 23:59:59', INTERVAL '1:1' MINUTE_SECOND);
+---------------------------------------------------------------+
| DATE_ADD('2100-12-31 23:59:59', INTERVAL '1:1' MINUTE_SECOND) |
+---------------------------------------------------------------+
| 2101-01-01 00:01:00                                           |
+---------------------------------------------------------------+

SELECT DATE_ADD('1900-01-01 00:00:00', INTERVAL '-1 10' DAY_HOUR);
+------------------------------------------------------------+
| DATE_ADD('1900-01-01 00:00:00', INTERVAL '-1 10' DAY_HOUR) |
+------------------------------------------------------------+
| 1899-12-30 14:00:00                                        |
+------------------------------------------------------------+

SELECT DATE_ADD('1992-12-31 23:59:59.000002', INTERVAL '1.999999' SECOND_MICROSECOND);
+--------------------------------------------------------------------------------+
| DATE_ADD('1992-12-31 23:59:59.000002', INTERVAL '1.999999' SECOND_MICROSECOND) |
+--------------------------------------------------------------------------------+
| 1993-01-01 00:00:01.000001                                                     |
+--------------------------------------------------------------------------------+

See Also

1.2.3.15 DATE_FORMAT

Syntax

DATE_FORMAT(date, format[, locale])

Contents

  1. Syntax
  2. Description
  3. Examples
  4. See Also

Description

Formats the date value according to the format string.

The language used for the names is controlled by the value of the lc_time_names system variable. See server locale for more on the supported locales.

The options that can be used by DATE_FORMAT(), as well as its inverse STR_TO_DATE() and the FROM_UNIXTIME() function, are:

OptionDescription
%aShort weekday name in current locale (Variable lc_time_names).
%bShort form month name in current locale. For locale en_US this is one of: Jan,Feb,Mar,Apr,May,Jun,Jul,Aug,Sep,Oct,Nov or Dec.
%cMonth with 1 or 2 digits.
%DDay with English suffix 'th', 'nd', 'st' or 'rd''. (1st, 2nd, 3rd...).
%dDay with 2 digits.
%eDay with 1 or 2 digits.
%fMicroseconds 6 digits.
%HHour with 2 digits between 00-23.
%hHour with 2 digits between 01-12.
%IHour with 2 digits between 01-12.
%iMinute with 2 digits.
%jDay of the year (001-366)
%kHour with 1 digits between 0-23.
%lHour with 1 digits between 1-12.
%MFull month name in current locale (Variable lc_time_names).
%mMonth with 2 digits.
%pAM/PM according to current locale (Variable lc_time_names).
%rTime in 12 hour format, followed by AM/PM. Short for '%I:%i:%S %p'.
%SSeconds with 2 digits.
%sSeconds with 2 digits.
%TTime in 24 hour format. Short for '%H:%i:%S'.
%UWeek number (00-53), when first day of the week is Sunday.
%uWeek number (00-53), when first day of the week is Monday.
%VWeek number (01-53), when first day of the week is Sunday. Used with %X.
%vWeek number (01-53), when first day of the week is Monday. Used with %x.
%WFull weekday name in current locale (Variable lc_time_names).
%wDay of the week. 0 = Sunday, 6 = Saturday.
%XYear with 4 digits when first day of the week is Sunday. Used with %V.
%xYear with 4 digits when first day of the week is Monday. Used with %v.
%YYear with 4 digits.
%yYear with 2 digits.
%#For str_to_date(), skip all numbers.
%.For str_to_date(), skip all punctation characters.
%@For str_to_date(), skip all alpha characters.
%%A literal % character.

To get a date in one of the standard formats, GET_FORMAT() can be used.

Examples

SELECT DATE_FORMAT('2009-10-04 22:23:00', '%W %M %Y');
+------------------------------------------------+
| DATE_FORMAT('2009-10-04 22:23:00', '%W %M %Y') |
+------------------------------------------------+
| Sunday October 2009                            |
+------------------------------------------------+

SELECT DATE_FORMAT('2007-10-04 22:23:00', '%H:%i:%s');
+------------------------------------------------+
| DATE_FORMAT('2007-10-04 22:23:00', '%H:%i:%s') |
+------------------------------------------------+
| 22:23:00                                       |
+------------------------------------------------+

SELECT DATE_FORMAT('1900-10-04 22:23:00', '%D %y %a %d %m %b %j');
+------------------------------------------------------------+
| DATE_FORMAT('1900-10-04 22:23:00', '%D %y %a %d %m %b %j') |
+------------------------------------------------------------+
| 4th 00 Thu 04 10 Oct 277                                   |
+------------------------------------------------------------+

SELECT DATE_FORMAT('1997-10-04 22:23:00', '%H %k %I %r %T %S %w');
+------------------------------------------------------------+
| DATE_FORMAT('1997-10-04 22:23:00', '%H %k %I %r %T %S %w') |
+------------------------------------------------------------+
| 22 22 10 10:23:00 PM 22:23:00 00 6                         |
+------------------------------------------------------------+

SELECT DATE_FORMAT('1999-01-01', '%X %V');
+------------------------------------+
| DATE_FORMAT('1999-01-01', '%X %V') |
+------------------------------------+
| 1998 52                            |
+------------------------------------+

SELECT DATE_FORMAT('2006-06-00', '%d');
+---------------------------------+
| DATE_FORMAT('2006-06-00', '%d') |
+---------------------------------+
| 00                              |
+---------------------------------+
MariaDB starting with 10.3.2

Optionally, the locale can be explicitly specified as the third DATE_FORMAT() argument. Doing so makes the function independent from the session settings, and the three argument version of DATE_FORMAT() can be used in virtual indexed and persistent generated-columns:

SELECT DATE_FORMAT('2006-01-01', '%W', 'el_GR');
+------------------------------------------+
| DATE_FORMAT('2006-01-01', '%W', 'el_GR') |
+------------------------------------------+
| Κυριακή                                  |
+------------------------------------------+

See Also

1.2.3.16 DATE_SUB

Syntax

DATE_SUB(date,INTERVAL expr unit)

Description

Performs date arithmetic. The date argument specifies the starting date or datetime value. expr is an expression specifying the interval value to be added or subtracted from the starting date. expr is a string; it may start with a "-" for negative intervals. unit is a keyword indicating the units in which the expression should be interpreted. See Date and Time Units for a complete list of permitted units.

See also DATE_ADD().

Examples

SELECT DATE_SUB('1998-01-02', INTERVAL 31 DAY);
+-----------------------------------------+
| DATE_SUB('1998-01-02', INTERVAL 31 DAY) |
+-----------------------------------------+
| 1997-12-02                              |
+-----------------------------------------+

SELECT DATE_SUB('2005-01-01 00:00:00', INTERVAL '1 1:1:1' DAY_SECOND);
+----------------------------------------------------------------+
| DATE_SUB('2005-01-01 00:00:00', INTERVAL '1 1:1:1' DAY_SECOND) |
+----------------------------------------------------------------+
| 2004-12-30 22:58:59                                            |
+----------------------------------------------------------------+

1.2.3.17 DAY

Syntax

DAY(date)

Description

DAY() is a synonym for DAYOFMONTH().

1.2.3.18 DAYNAME

Syntax

DAYNAME(date)

Description

Returns the name of the weekday for date. The language used for the name is controlled by the value of the lc_time_names system variable. See server locale for more on the supported locales.

Examples

SELECT DAYNAME('2007-02-03');
+-----------------------+
| DAYNAME('2007-02-03') |
+-----------------------+
| Saturday              |
+-----------------------+

CREATE TABLE t1 (d DATETIME);
INSERT INTO t1 VALUES
    ("2007-01-30 21:31:07"),
    ("1983-10-15 06:42:51"),
    ("2011-04-21 12:34:56"),
    ("2011-10-30 06:31:41"),
    ("2011-01-30 14:03:25"),
    ("2004-10-07 11:19:34");

SELECT d, DAYNAME(d) FROM t1;
+---------------------+------------+
| d                   | DAYNAME(d) |
+---------------------+------------+
| 2007-01-30 21:31:07 | Tuesday    |
| 1983-10-15 06:42:51 | Saturday   |
| 2011-04-21 12:34:56 | Thursday   |
| 2011-10-30 06:31:41 | Sunday     |
| 2011-01-30 14:03:25 | Sunday     |
| 2004-10-07 11:19:34 | Thursday   |
+---------------------+------------+

Changing the locale:

SET lc_time_names = 'fr_CA';

SELECT DAYNAME('2013-04-01');
+-----------------------+
| DAYNAME('2013-04-01') |
+-----------------------+
| lundi                 |
+-----------------------+

1.2.3.19 DAYOFMONTH

Syntax

DAYOFMONTH(date)

Description

Returns the day of the month for date, in the range 1 to 31, or 0 for dates such as '0000-00-00' or '2008-00-00' which have a zero day part.

DAY() is a synonym.

Examples

SELECT DAYOFMONTH('2007-02-03');
+--------------------------+
| DAYOFMONTH('2007-02-03') |
+--------------------------+
|                        3 |
+--------------------------+

CREATE TABLE t1 (d DATETIME);
INSERT INTO t1 VALUES
    ("2007-01-30 21:31:07"),
    ("1983-10-15 06:42:51"),
    ("2011-04-21 12:34:56"),
    ("2011-10-30 06:31:41"),
    ("2011-01-30 14:03:25"),
    ("2004-10-07 11:19:34");

SELECT d FROM t1 where DAYOFMONTH(d) = 30;
+---------------------+
| d                   |
+---------------------+
| 2007-01-30 21:31:07 |
| 2011-10-30 06:31:41 |
| 2011-01-30 14:03:25 |
+---------------------+

1.2.3.20 DAYOFWEEK

Syntax

DAYOFWEEK(date)

Description

Returns the day of the week index for the date (1 = Sunday, 2 = Monday, ..., 7 = Saturday). These index values correspond to the ODBC standard.

This contrasts with WEEKDAY() which follows a different index numbering (0 = Monday, 1 = Tuesday, ... 6 = Sunday).

Examples

SELECT DAYOFWEEK('2007-02-03');
+-------------------------+
| DAYOFWEEK('2007-02-03') |
+-------------------------+
|                       7 |
+-------------------------+

CREATE TABLE t1 (d DATETIME);
INSERT INTO t1 VALUES
    ("2007-01-30 21:31:07"),
    ("1983-10-15 06:42:51"),
    ("2011-04-21 12:34:56"),
    ("2011-10-30 06:31:41"),
    ("2011-01-30 14:03:25"),
    ("2004-10-07 11:19:34");

SELECT d, DAYNAME(d), DAYOFWEEK(d), WEEKDAY(d) from t1;
+---------------------+------------+--------------+------------+
| d                   | DAYNAME(d) | DAYOFWEEK(d) | WEEKDAY(d) |
+---------------------+------------+--------------+------------+
| 2007-01-30 21:31:07 | Tuesday    |            3 |          1 |
| 1983-10-15 06:42:51 | Saturday   |            7 |          5 |
| 2011-04-21 12:34:56 | Thursday   |            5 |          3 |
| 2011-10-30 06:31:41 | Sunday     |            1 |          6 |
| 2011-01-30 14:03:25 | Sunday     |            1 |          6 |
| 2004-10-07 11:19:34 | Thursday   |            5 |          3 |
+---------------------+------------+--------------+------------+

1.2.3.21 DAYOFYEAR

Syntax

DAYOFYEAR(date)

Description

Returns the day of the year for date, in the range 1 to 366.

Examples

SELECT DAYOFYEAR('2018-02-16');
+-------------------------+
| DAYOFYEAR('2018-02-16') |
+-------------------------+
|                      47 |
+-------------------------+

1.2.3.22 EXTRACT

Syntax

EXTRACT(unit FROM date)

Contents

  1. Syntax
  2. Description
  3. Examples
  4. See Also

Description

The EXTRACT() function extracts the required unit from the date. See Date and Time Units for a complete list of permitted units.

In MariaDB 10.0.7 and MariaDB 5.5.35, EXTRACT (HOUR FROM ...) was changed to return a value from 0 to 23, adhering to the SQL standard. Until MariaDB 10.0.6 and MariaDB 5.5.34, and in all versions of MySQL at least as of MySQL 5.7, it could return a value > 23. HOUR() is not a standard function, so continues to adhere to the old behaviour inherited from MySQL.

Examples

SELECT EXTRACT(YEAR FROM '2009-07-02');
+---------------------------------+
| EXTRACT(YEAR FROM '2009-07-02') |
+---------------------------------+
|                            2009 |
+---------------------------------+

SELECT EXTRACT(YEAR_MONTH FROM '2009-07-02 01:02:03');
+------------------------------------------------+
| EXTRACT(YEAR_MONTH FROM '2009-07-02 01:02:03') |
+------------------------------------------------+
|                                         200907 |
+------------------------------------------------+

SELECT EXTRACT(DAY_MINUTE FROM '2009-07-02 01:02:03');
+------------------------------------------------+
| EXTRACT(DAY_MINUTE FROM '2009-07-02 01:02:03') |
+------------------------------------------------+
|                                          20102 |
+------------------------------------------------+

SELECT EXTRACT(MICROSECOND FROM '2003-01-02 10:30:00.000123');
+--------------------------------------------------------+
| EXTRACT(MICROSECOND FROM '2003-01-02 10:30:00.000123') |
+--------------------------------------------------------+
|                                                    123 |
+--------------------------------------------------------+

From MariaDB 10.0.7 and MariaDB 5.5.35, EXTRACT (HOUR FROM...) returns a value from 0 to 23, as per the SQL standard. HOUR is not a standard function, so continues to adhere to the old behaviour inherited from MySQL.

SELECT EXTRACT(HOUR FROM '26:30:00'), HOUR('26:30:00');
+-------------------------------+------------------+
| EXTRACT(HOUR FROM '26:30:00') | HOUR('26:30:00') |
+-------------------------------+------------------+
|                             2 |               26 |
+-------------------------------+------------------+

See Also

1.2.3.23 FROM_DAYS

Syntax

FROM_DAYS(N)

Description

Given a day number N, returns a DATE value. The day count is based on the number of days from the start of the standard calendar (0000-00-00).

The function is not designed for use with dates before the advent of the Gregorian calendar in October 1582. Results will not be reliable since it doesn't account for the lost days when the calendar changed from the Julian calendar.

This is the converse of the TO_DAYS() function.

Examples

SELECT FROM_DAYS(730669);
+-------------------+
| FROM_DAYS(730669) |
+-------------------+
| 2000-07-03        |
+-------------------+

1.2.3.24 FROM_UNIXTIME

Syntax

FROM_UNIXTIME(unix_timestamp), FROM_UNIXTIME(unix_timestamp,format)

Contents

  1. Syntax
  2. Description
  3. Performance Considerations
  4. Examples
  5. See Also

Description

Returns a representation of the unix_timestamp argument as a value in 'YYYY-MM-DD HH:MM:SS' or YYYYMMDDHHMMSS.uuuuuu format, depending on whether the function is used in a string or numeric context. The value is expressed in the current time zone. unix_timestamp is an internal timestamp value such as is produced by the UNIX_TIMESTAMP() function.

If format is given, the result is formatted according to the format string, which is used the same way as listed in the entry for the DATE_FORMAT() function.

Timestamps in MariaDB have a maximum value of 2147483647, equivalent to 2038-01-19 05:14:07. This is due to the underlying 32-bit limitation. Using the function on a timestamp beyond this will result in NULL being returned. Use DATETIME as a storage type if you require dates beyond this.

The options that can be used by FROM_UNIXTIME(), as well as DATE_FORMAT() and STR_TO_DATE(), are:

OptionDescription
%aShort weekday name in current locale (Variable lc_time_names).
%bShort form month name in current locale. For locale en_US this is one of: Jan,Feb,Mar,Apr,May,Jun,Jul,Aug,Sep,Oct,Nov or Dec.
%cMonth with 1 or 2 digits.
%DDay with English suffix 'th', 'nd', 'st' or 'rd''. (1st, 2nd, 3rd...).
%dDay with 2 digits.
%eDay with 1 or 2 digits.
%fMicroseconds 6 digits.
%HHour with 2 digits between 00-23.
%hHour with 2 digits between 01-12.
%IHour with 2 digits between 01-12.
%iMinute with 2 digits.
%jDay of the year (001-366)
%kHour with 1 digits between 0-23.
%lHour with 1 digits between 1-12.
%MFull month name in current locale (Variable lc_time_names).
%mMonth with 2 digits.
%pAM/PM according to current locale (Variable lc_time_names).
%rTime in 12 hour format, followed by AM/PM. Short for '%I:%i:%S %p'.
%SSeconds with 2 digits.
%sSeconds with 2 digits.
%TTime in 24 hour format. Short for '%H:%i:%S'.
%UWeek number (00-53), when first day of the week is Sunday.
%uWeek number (00-53), when first day of the week is Monday.
%VWeek number (01-53), when first day of the week is Sunday. Used with %X.
%vWeek number (01-53), when first day of the week is Monday. Used with %x.
%WFull weekday name in current locale (Variable lc_time_names).
%wDay of the week. 0 = Sunday, 6 = Saturday.
%XYear with 4 digits when first day of the week is Sunday. Used with %V.
%xYear with 4 digits when first day of the week is Sunday. Used with %v.
%YYear with 4 digits.
%yYear with 2 digits.
%#For str_to_date(), skip all numbers.
%.For str_to_date(), skip all punctation characters.
%@For str_to_date(), skip all alpha characters.
%%A literal % character.

Performance Considerations

If your session time zone is set to SYSTEM (the default), FROM_UNIXTIME() will call the OS function to convert the data using the system time zone. At least on Linux, the corresponding function (localtime_r) uses a global mutex inside glibc that can cause contention under high concurrent load.

Set your time zone to a named time zone to avoid this issue. See mysql time zone tables for details on how to do this.

Examples

SELECT FROM_UNIXTIME(1196440219);
+---------------------------+
| FROM_UNIXTIME(1196440219) |
+---------------------------+
| 2007-11-30 11:30:19       |
+---------------------------+

SELECT FROM_UNIXTIME(1196440219) + 0;
+-------------------------------+
| FROM_UNIXTIME(1196440219) + 0 |
+-------------------------------+
|         20071130113019.000000 |
+-------------------------------+

SELECT FROM_UNIXTIME(UNIX_TIMESTAMP(), '%Y %D %M %h:%i:%s %x');
+---------------------------------------------------------+
| FROM_UNIXTIME(UNIX_TIMESTAMP(), '%Y %D %M %h:%i:%s %x') |
+---------------------------------------------------------+
| 2010 27th March 01:03:47 2010                           |
+---------------------------------------------------------+

See Also

1.2.3.25 GET_FORMAT

Syntax

GET_FORMAT({DATE|DATETIME|TIME}, {'EUR'|'USA'|'JIS'|'ISO'|'INTERNAL'})

Description

Returns a format string. This function is useful in combination with the DATE_FORMAT() and the STR_TO_DATE() functions.

Possible result formats are:

Function CallResult Format
GET_FORMAT(DATE,'EUR')'%d.%m.%Y'
GET_FORMAT(DATE,'USA')'%m.%d.%Y'
GET_FORMAT(DATE,'JIS')'%Y-%m-%d'
GET_FORMAT(DATE,'ISO')'%Y-%m-%d'
GET_FORMAT(DATE,'INTERNAL')'%Y%m%d'
GET_FORMAT(DATETIME,'EUR')'%Y-%m-%d %H.%i.%s'
GET_FORMAT(DATETIME,'USA')'%Y-%m-%d %H.%i.%s'
GET_FORMAT(DATETIME,'JIS')'%Y-%m-%d %H:%i:%s'
GET_FORMAT(DATETIME,'ISO')'%Y-%m-%d %H:%i:%s'
GET_FORMAT(DATETIME,'INTERNAL')'%Y%m%d%H%i%s'
GET_FORMAT(TIME,'EUR')'%H.%i.%s'
GET_FORMAT(TIME,'USA')'%h:%i:%s %p'
GET_FORMAT(TIME,'JIS')'%H:%i:%s'
GET_FORMAT(TIME,'ISO')'%H:%i:%s'
GET_FORMAT(TIME,'INTERNAL')'%H%i%s'

Examples

Obtaining the string matching to the standard European date format:

SELECT GET_FORMAT(DATE, 'EUR');
+-------------------------+
| GET_FORMAT(DATE, 'EUR') |
+-------------------------+
| %d.%m.%Y                |
+-------------------------+

Using the same string to format a date:

SELECT DATE_FORMAT('2003-10-03',GET_FORMAT(DATE,'EUR'));
+--------------------------------------------------+
| DATE_FORMAT('2003-10-03',GET_FORMAT(DATE,'EUR')) |
+--------------------------------------------------+
| 03.10.2003                                       |
+--------------------------------------------------+

SELECT STR_TO_DATE('10.31.2003',GET_FORMAT(DATE,'USA'));
+--------------------------------------------------+
| STR_TO_DATE('10.31.2003',GET_FORMAT(DATE,'USA')) |
+--------------------------------------------------+
| 2003-10-31                                       |
+--------------------------------------------------+

1.2.3.26 HOUR

Syntax

HOUR(time)

Description

Returns the hour for time. The range of the return value is 0 to 23 for time-of-day values. However, the range of TIME values actually is much larger, so HOUR can return values greater than 23.

The return value is always positive, even if a negative TIME value is provided.

Examples

SELECT HOUR('10:05:03');
+------------------+
| HOUR('10:05:03') |
+------------------+
|               10 |
+------------------+

SELECT HOUR('272:59:59');
+-------------------+
| HOUR('272:59:59') |
+-------------------+
|               272 |
+-------------------+

Difference between EXTRACT (HOUR FROM ...) (>= MariaDB 10.0.7 and MariaDB 5.5.35) and HOUR:

SELECT EXTRACT(HOUR FROM '26:30:00'), HOUR('26:30:00');
+-------------------------------+------------------+
| EXTRACT(HOUR FROM '26:30:00') | HOUR('26:30:00') |
+-------------------------------+------------------+
|                             2 |               26 |
+-------------------------------+------------------+

See Also

1.2.3.27 LAST_DAY

Syntax

LAST_DAY(date)

Description

Takes a date or datetime value and returns the corresponding value for the last day of the month. Returns NULL if the argument is invalid.

Examples

SELECT LAST_DAY('2003-02-05');
+------------------------+
| LAST_DAY('2003-02-05') |
+------------------------+
| 2003-02-28             |
+------------------------+

SELECT LAST_DAY('2004-02-05');
+------------------------+
| LAST_DAY('2004-02-05') |
+------------------------+
| 2004-02-29             |
+------------------------+

SELECT LAST_DAY('2004-01-01 01:01:01');
+---------------------------------+
| LAST_DAY('2004-01-01 01:01:01') |
+---------------------------------+
| 2004-01-31                      |
+---------------------------------+

SELECT LAST_DAY('2003-03-32');
+------------------------+
| LAST_DAY('2003-03-32') |
+------------------------+
| NULL                   |
+------------------------+
1 row in set, 1 warning (0.00 sec)

Warning (Code 1292): Incorrect datetime value: '2003-03-32'

1.2.3.28 LOCALTIME

Syntax

LOCALTIME
LOCALTIME([precision])

Description

LOCALTIME and LOCALTIME() are synonyms for NOW().

See Also

1.2.3.29 LOCALTIMESTAMP

Syntax

LOCALTIMESTAMP
LOCALTIMESTAMP([precision])

Description

LOCALTIMESTAMP and LOCALTIMESTAMP() are synonyms for NOW().

See Also

1.2.3.30 MAKEDATE

Syntax

MAKEDATE(year,dayofyear)

Description

Returns a date, given year and day-of-year values. dayofyear must be greater than 0 or the result is NULL.

Examples

SELECT MAKEDATE(2011,31), MAKEDATE(2011,32);
+-------------------+-------------------+
| MAKEDATE(2011,31) | MAKEDATE(2011,32) |
+-------------------+-------------------+
| 2011-01-31        | 2011-02-01        |
+-------------------+-------------------+

SELECT MAKEDATE(2011,365), MAKEDATE(2014,365);
+--------------------+--------------------+
| MAKEDATE(2011,365) | MAKEDATE(2014,365) |
+--------------------+--------------------+
| 2011-12-31         | 2014-12-31         |
+--------------------+--------------------+

SELECT MAKEDATE(2011,0);
+------------------+
| MAKEDATE(2011,0) |
+------------------+
| NULL             |
+------------------+

1.2.3.31 MAKETIME

Syntax

MAKETIME(hour,minute,second)

Description

Returns a time value calculated from the hour, minute, and second arguments.

If minute or second are out of the range 0 to 60, NULL is returned. The hour can be in the range -838 to 838, outside of which the value is truncated with a warning.

Examples

SELECT MAKETIME(13,57,33);
+--------------------+
| MAKETIME(13,57,33) |
+--------------------+
| 13:57:33           |
+--------------------+

SELECT MAKETIME(-13,57,33);
+---------------------+
| MAKETIME(-13,57,33) |
+---------------------+
| -13:57:33           |
+---------------------+

SELECT MAKETIME(13,67,33);
+--------------------+
| MAKETIME(13,67,33) |
+--------------------+
| NULL               |
+--------------------+

SELECT MAKETIME(-1000,57,33);
+-----------------------+
| MAKETIME(-1000,57,33) |
+-----------------------+
| -838:59:59            |
+-----------------------+
1 row in set, 1 warning (0.00 sec)

SHOW WARNINGS;
+---------+------+-----------------------------------------------+
| Level   | Code | Message                                       |
+---------+------+-----------------------------------------------+
| Warning | 1292 | Truncated incorrect time value: '-1000:57:33' |
+---------+------+-----------------------------------------------+

1.2.3.32 MICROSECOND

Syntax

MICROSECOND(expr)

Contents

  1. Syntax
  2. Description
  3. Examples
  4. See Also

Description

Returns the microseconds from the time or datetime expression expr as a number in the range from 0 to 999999.

If expr is a time with no microseconds, zero is returned, while if expr is a date with no time, zero with a warning is returned.

Examples

SELECT MICROSECOND('12:00:00.123456');
+--------------------------------+
| MICROSECOND('12:00:00.123456') |
+--------------------------------+
|                         123456 |
+--------------------------------+

SELECT MICROSECOND('2009-12-31 23:59:59.000010');
+-------------------------------------------+
| MICROSECOND('2009-12-31 23:59:59.000010') |
+-------------------------------------------+
|                                        10 |
+-------------------------------------------+

SELECT MICROSECOND('2013-08-07 12:13:14');
+------------------------------------+
| MICROSECOND('2013-08-07 12:13:14') |
+------------------------------------+
|                                  0 |
+------------------------------------+

SELECT MICROSECOND('2013-08-07');
+---------------------------+
| MICROSECOND('2013-08-07') |
+---------------------------+
|                         0 |
+---------------------------+
1 row in set, 1 warning (0.00 sec)

SHOW WARNINGS;
+---------+------+----------------------------------------------+
| Level   | Code | Message                                      |
+---------+------+----------------------------------------------+
| Warning | 1292 | Truncated incorrect time value: '2013-08-07' |
+---------+------+----------------------------------------------+

See Also

1.2.3.33 MINUTE

Syntax

MINUTE(time)

Description

Returns the minute for time, in the range 0 to 59.

Examples

SELECT MINUTE('2013-08-03 11:04:03');
+-------------------------------+
| MINUTE('2013-08-03 11:04:03') |
+-------------------------------+
|                             4 |
+-------------------------------+

 SELECT MINUTE ('23:12:50');
+---------------------+
| MINUTE ('23:12:50') |
+---------------------+
|                  12 |
+---------------------+

1.2.3.34 MONTH

Syntax

MONTH(date)

Description

Returns the month for date in the range 1 to 12 for January to December, or 0 for dates such as '0000-00-00' or '2008-00-00' that have a zero month part.

Examples

SELECT MONTH('2019-01-03');
+---------------------+
| MONTH('2019-01-03') |
+---------------------+
|                   1 |
+---------------------+

SELECT MONTH('2019-00-03');
+---------------------+
| MONTH('2019-00-03') |
+---------------------+
|                   0 |
+---------------------+

1.2.3.35 MONTHNAME

Syntax

MONTHNAME(date)

Description

Returns the full name of the month for date. The language used for the name is controlled by the value of the lc_time_names system variable. See server locale for more on the supported locales.

Examples

SELECT MONTHNAME('2019-02-03');
+-------------------------+
| MONTHNAME('2019-02-03') |
+-------------------------+
| February                |
+-------------------------+

Changing the locale:

SET lc_time_names = 'fr_CA';

SELECT MONTHNAME('2019-05-21');
+-------------------------+
| MONTHNAME('2019-05-21') |
+-------------------------+
| mai                     |
+-------------------------+

1.2.3.36 NOW

Syntax

NOW([precision])
CURRENT_TIMESTAMP
CURRENT_TIMESTAMP([precision])
LOCALTIME, LOCALTIME([precision])
LOCALTIMESTAMP
LOCALTIMESTAMP([precision])

Contents

  1. Syntax
  2. Description
  3. Examples
  4. See Also

Description

Returns the current date and time as a value in 'YYYY-MM-DD HH:MM:SS' or YYYYMMDDHHMMSS.uuuuuu format, depending on whether the function is used in a string or numeric context. The value is expressed in the current time zone.

The optional precision determines the microsecond precision. See Microseconds in MariaDB.

NOW() (or its synonyms) can be used as the default value for TIMESTAMP columns as well as, since MariaDB 10.0.1, DATETIME columns. Before MariaDB 10.0.1, it was only possible for a single TIMESTAMP column per table to contain the CURRENT_TIMESTAMP as its default.

When displayed in the INFORMATION_SCHEMA.COLUMNS table, a default CURRENT TIMESTAMP is displayed as CURRENT_TIMESTAMP up until MariaDB 10.2.2, and as current_timestamp() from MariaDB 10.2.3, due to to MariaDB 10.2 accepting expressions in the DEFAULT clause.

Examples

SELECT NOW();
+---------------------+
| NOW()               |
+---------------------+
| 2010-03-27 13:13:25 |
+---------------------+

SELECT NOW() + 0;
+-----------------------+
| NOW() + 0             |
+-----------------------+
| 20100327131329.000000 |
+-----------------------+

With precision:

SELECT CURRENT_TIMESTAMP(2);
+------------------------+
| CURRENT_TIMESTAMP(2)   |
+------------------------+
| 2018-07-10 09:47:26.24 |
+------------------------+

Used as a default TIMESTAMP:

CREATE TABLE t (createdTS TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP);

From MariaDB 10.2.2:

SELECT * FROM INFORMATION_SCHEMA.COLUMNS WHERE TABLE_SCHEMA='test'
  AND COLUMN_NAME LIKE '%ts%'\G
*************************** 1. row ***************************
           TABLE_CATALOG: def
            TABLE_SCHEMA: test
              TABLE_NAME: t
             COLUMN_NAME: ts
        ORDINAL_POSITION: 1
          COLUMN_DEFAULT: current_timestamp()
...

<= MariaDB 10.2.1

SELECT * FROM INFORMATION_SCHEMA.COLUMNS WHERE TABLE_SCHEMA='test'
  AND COLUMN_NAME LIKE '%ts%'\G
*************************** 1. row ***************************
           TABLE_CATALOG: def
            TABLE_SCHEMA: test
              TABLE_NAME: t
             COLUMN_NAME: createdTS
        ORDINAL_POSITION: 1
          COLUMN_DEFAULT: CURRENT_TIMESTAMP
...

See Also

1.2.3.37 PERIOD_ADD

Syntax

PERIOD_ADD(P,N)

Description

Adds N months to period P. P is in the format YYMM or YYYYMM, and is not a date value. If P contains a two-digit year, values from 00 to 69 are converted to from 2000 to 2069, while values from 70 are converted to 1970 upwards.

Returns a value in the format YYYYMM.

Examples

SELECT PERIOD_ADD(200801,2);
+----------------------+
| PERIOD_ADD(200801,2) |
+----------------------+
|               200803 |
+----------------------+

SELECT PERIOD_ADD(6910,2);
+--------------------+
| PERIOD_ADD(6910,2) |
+--------------------+
|             206912 |
+--------------------+

SELECT PERIOD_ADD(7010,2);
+--------------------+
| PERIOD_ADD(7010,2) |
+--------------------+
|             197012 |
+--------------------+

1.2.3.38 PERIOD_DIFF

Syntax

PERIOD_DIFF(P1,P2)

Description

Returns the number of months between periods P1 and P2. P1 and P2 can be in the format YYMM or YYYYMM, and are not date values.

If P1 or P2 contains a two-digit year, values from 00 to 69 are converted to from 2000 to 2069, while values from 70 are converted to 1970 upwards.

Examples

SELECT PERIOD_DIFF(200802,200703);
+----------------------------+
| PERIOD_DIFF(200802,200703) |
+----------------------------+
|                         11 |
+----------------------------+

SELECT PERIOD_DIFF(6902,6803);
+------------------------+
| PERIOD_DIFF(6902,6803) |
+------------------------+
|                     11 |
+------------------------+

SELECT PERIOD_DIFF(7002,6803);
+------------------------+
| PERIOD_DIFF(7002,6803) |
+------------------------+
|                  -1177 |
+------------------------+

1.2.3.39 QUARTER

Syntax

QUARTER(date)

Description

Returns the quarter of the year for date, in the range 1 to 4. Returns 0 if month contains a zero value, or NULL if the given value is not otherwise a valid date (zero values are accepted).

Examples

SELECT QUARTER('2008-04-01');
+-----------------------+
| QUARTER('2008-04-01') |
+-----------------------+
|                     2 |
+-----------------------+

SELECT QUARTER('2019-00-01');
+-----------------------+
| QUARTER('2019-00-01') |
+-----------------------+
|                     0 |
+-----------------------+

1.2.3.40 SECOND

Syntax

SECOND(time)

Description

Returns the second for a given time (which can include microseconds), in the range 0 to 59, or NULL if not given a valid time value.

Examples

SELECT SECOND('10:05:03');
+--------------------+
| SECOND('10:05:03') |
+--------------------+
|                  3 |
+--------------------+

SELECT SECOND('10:05:01.999999');
+---------------------------+
| SECOND('10:05:01.999999') |
+---------------------------+
|                         1 |
+---------------------------+

1.2.3.41 SEC_TO_TIME

Syntax

SEC_TO_TIME(seconds)

Description

Returns the seconds argument, converted to hours, minutes, and seconds, as a TIME value. The range of the result is constrained to that of the TIME data type. A warning occurs if the argument corresponds to a value outside that range.

The time will be returned in the format hh:mm:ss, or hhmmss if used in a numeric calculation.

Examples

SELECT SEC_TO_TIME(12414);
+--------------------+
| SEC_TO_TIME(12414) |
+--------------------+
| 03:26:54           |
+--------------------+

SELECT SEC_TO_TIME(12414)+0;
+----------------------+
| SEC_TO_TIME(12414)+0 |
+----------------------+
|                32654 |
+----------------------+

SELECT SEC_TO_TIME(9999999);
+----------------------+
| SEC_TO_TIME(9999999) |
+----------------------+
| 838:59:59            |
+----------------------+
1 row in set, 1 warning (0.00 sec)

SHOW WARNINGS;
+---------+------+-------------------------------------------+
| Level   | Code | Message                                   |
+---------+------+-------------------------------------------+
| Warning | 1292 | Truncated incorrect time value: '9999999' |
+---------+------+-------------------------------------------+

1.2.3.42 STR_TO_DATE

Syntax

STR_TO_DATE(str,format)

Contents

  1. Syntax
  2. Description
  3. Examples
  4. See Also

Description

This is the inverse of the DATE_FORMAT() function. It takes a string str and a format string format. STR_TO_DATE() returns a DATETIME value if the format string contains both date and time parts, or a DATE or TIME value if the string contains only date or time parts.

The date, time, or datetime values contained in str should be given in the format indicated by format. If str contains an illegal date, time, or datetime value, STR_TO_DATE() returns NULL. An illegal value also produces a warning.

The options that can be used by STR_TO_DATE(), as well as its inverse DATE_FORMAT() and the FROM_UNIXTIME() function, are:

OptionDescription
%aShort weekday name in current locale (Variable lc_time_names).
%bShort form month name in current locale. For locale en_US this is one of: Jan,Feb,Mar,Apr,May,Jun,Jul,Aug,Sep,Oct,Nov or Dec.
%cMonth with 1 or 2 digits.
%DDay with English suffix 'th', 'nd', 'st' or 'rd''. (1st, 2nd, 3rd...).
%dDay with 2 digits.
%eDay with 1 or 2 digits.
%fMicroseconds 6 digits.
%HHour with 2 digits between 00-23.
%hHour with 2 digits between 01-12.
%IHour with 2 digits between 01-12.
%iMinute with 2 digits.
%jDay of the year (001-366)
%kHour with 1 digits between 0-23.
%lHour with 1 digits between 1-12.
%MFull month name in current locale (Variable lc_time_names).
%mMonth with 2 digits.
%pAM/PM according to current locale (Variable lc_time_names).
%rTime in 12 hour format, followed by AM/PM. Short for '%I:%i:%S %p'.
%SSeconds with 2 digits.
%sSeconds with 2 digits.
%TTime in 24 hour format. Short for '%H:%i:%S'.
%UWeek number (00-53), when first day of the week is Sunday.
%uWeek number (00-53), when first day of the week is Monday.
%VWeek number (01-53), when first day of the week is Sunday. Used with %X.
%vWeek number (01-53), when first day of the week is Monday. Used with %x.
%WFull weekday name in current locale (Variable lc_time_names).
%wDay of the week. 0 = Sunday, 6 = Saturday.
%XYear with 4 digits when first day of the week is Sunday. Used with %V.
%xYear with 4 digits when first day of the week is Monday. Used with %v.
%YYear with 4 digits.
%yYear with 2 digits.
%#For str_to_date(), skip all numbers.
%.For str_to_date(), skip all punctation characters.
%@For str_to_date(), skip all alpha characters.
%%A literal % character.

Examples

SELECT STR_TO_DATE('Wednesday, June 2, 2014', '%W, %M %e, %Y');
+---------------------------------------------------------+
| STR_TO_DATE('Wednesday, June 2, 2014', '%W, %M %e, %Y') |
+---------------------------------------------------------+
| 2014-06-02                                              |
+---------------------------------------------------------+


SELECT STR_TO_DATE('Wednesday23423, June 2, 2014', '%W, %M %e, %Y');
+--------------------------------------------------------------+
| STR_TO_DATE('Wednesday23423, June 2, 2014', '%W, %M %e, %Y') |
+--------------------------------------------------------------+
| NULL                                                         |
+--------------------------------------------------------------+
1 row in set, 1 warning (0.00 sec)

SHOW WARNINGS;
+---------+------+-----------------------------------------------------------------------------------+
| Level   | Code | Message                                                                           |
+---------+------+-----------------------------------------------------------------------------------+
| Warning | 1411 | Incorrect datetime value: 'Wednesday23423, June 2, 2014' for function str_to_date |
+---------+------+-----------------------------------------------------------------------------------+

SELECT STR_TO_DATE('Wednesday23423, June 2, 2014', '%W%#, %M %e, %Y');
+----------------------------------------------------------------+
| STR_TO_DATE('Wednesday23423, June 2, 2014', '%W%#, %M %e, %Y') |
+----------------------------------------------------------------+
| 2014-06-02                                                     |
+----------------------------------------------------------------+

See Also

1.2.3.43 SUBDATE

Syntax

SUBDATE(date,INTERVAL expr unit), SUBDATE(expr,days)

Description

When invoked with the INTERVAL form of the second argument, SUBDATE() is a synonym for DATE_SUB(). See Date and Time Units for a complete list of permitted units.

The second form allows the use of an integer value for days. In such cases, it is interpreted as the number of days to be subtracted from the date or datetime expression expr.

Examples

SELECT DATE_SUB('2008-01-02', INTERVAL 31 DAY);
+-----------------------------------------+
| DATE_SUB('2008-01-02', INTERVAL 31 DAY) |
+-----------------------------------------+
| 2007-12-02                              |
+-----------------------------------------+

SELECT SUBDATE('2008-01-02', INTERVAL 31 DAY);
+----------------------------------------+
| SUBDATE('2008-01-02', INTERVAL 31 DAY) |
+----------------------------------------+
| 2007-12-02                             |
+----------------------------------------+

SELECT SUBDATE('2008-01-02 12:00:00', 31);
+------------------------------------+
| SUBDATE('2008-01-02 12:00:00', 31) |
+------------------------------------+
| 2007-12-02 12:00:00                |
+------------------------------------+

CREATE TABLE t1 (d DATETIME);
INSERT INTO t1 VALUES
    ("2007-01-30 21:31:07"),
    ("1983-10-15 06:42:51"),
    ("2011-04-21 12:34:56"),
    ("2011-10-30 06:31:41"),
    ("2011-01-30 14:03:25"),
    ("2004-10-07 11:19:34");

SELECT d, SUBDATE(d, 10) from t1;
+---------------------+---------------------+
| d                   | SUBDATE(d, 10)      |
+---------------------+---------------------+
| 2007-01-30 21:31:07 | 2007-01-20 21:31:07 |
| 1983-10-15 06:42:51 | 1983-10-05 06:42:51 |
| 2011-04-21 12:34:56 | 2011-04-11 12:34:56 |
| 2011-10-30 06:31:41 | 2011-10-20 06:31:41 |
| 2011-01-30 14:03:25 | 2011-01-20 14:03:25 |
| 2004-10-07 11:19:34 | 2004-09-27 11:19:34 |
+---------------------+---------------------+

SELECT d, SUBDATE(d, INTERVAL 10 MINUTE) from t1;
+---------------------+--------------------------------+
| d                   | SUBDATE(d, INTERVAL 10 MINUTE) |
+---------------------+--------------------------------+
| 2007-01-30 21:31:07 | 2007-01-30 21:21:07            |
| 1983-10-15 06:42:51 | 1983-10-15 06:32:51            |
| 2011-04-21 12:34:56 | 2011-04-21 12:24:56            |
| 2011-10-30 06:31:41 | 2011-10-30 06:21:41            |
| 2011-01-30 14:03:25 | 2011-01-30 13:53:25            |
| 2004-10-07 11:19:34 | 2004-10-07 11:09:34            |
+---------------------+--------------------------------+

1.2.3.44 SUBTIME

Syntax

SUBTIME(expr1,expr2)

Description

SUBTIME() returns expr1 - expr2 expressed as a value in the same format as expr1. expr1 is a time or datetime expression, and expr2 is a time expression.

Examples

SELECT SUBTIME('2007-12-31 23:59:59.999999','1 1:1:1.000002');
+--------------------------------------------------------+
| SUBTIME('2007-12-31 23:59:59.999999','1 1:1:1.000002') |
+--------------------------------------------------------+
| 2007-12-30 22:58:58.999997                             |
+--------------------------------------------------------+

SELECT SUBTIME('01:00:00.999999', '02:00:00.999998');
+-----------------------------------------------+
| SUBTIME('01:00:00.999999', '02:00:00.999998') |
+-----------------------------------------------+
| -00:59:59.999999                              |
+-----------------------------------------------+

1.2.3.45 SYSDATE

Syntax

SYSDATE([precision])

Contents

  1. Syntax
  2. Description
  3. Examples
  4. See Also

Description

Returns the current date and time as a value in 'YYYY-MM-DD HH:MM:SS' or YYYYMMDDHHMMSS.uuuuuu format, depending on whether the function is used in a string or numeric context.

The optional precision determines the microsecond precision. See Microseconds in MariaDB.

SYSDATE() returns the time at which it executes. This differs from the behavior for NOW(), which returns a constant time that indicates the time at which the statement began to execute. (Within a stored routine or trigger, NOW() returns the time at which the routine or triggering statement began to execute.)

In addition, changing the timestamp system variable with a SET timestamp statement affects the value returned by NOW() but not by SYSDATE(). This means that timestamp settings in the binary log have no effect on invocations of SYSDATE().

Because SYSDATE() can return different values even within the same statement, and is not affected by SET TIMESTAMP, it is non-deterministic and therefore unsafe for replication if statement-based binary logging is used. If that is a problem, you can use row-based logging, or start the server with the mysqld option --sysdate-is-now to cause SYSDATE() to be an alias for NOW(). The non-deterministic nature of SYSDATE() also means that indexes cannot be used for evaluating expressions that refer to it, and that statements using the SYSDATE() function are unsafe for statement-based replication.

Examples

Difference between NOW() and SYSDATE():

SELECT NOW(), SLEEP(2), NOW();
+---------------------+----------+---------------------+
| NOW()               | SLEEP(2) | NOW()               |
+---------------------+----------+---------------------+
| 2010-03-27 13:23:40 |        0 | 2010-03-27 13:23:40 |
+---------------------+----------+---------------------+

SELECT SYSDATE(), SLEEP(2), SYSDATE();
+---------------------+----------+---------------------+
| SYSDATE()           | SLEEP(2) | SYSDATE()           |
+---------------------+----------+---------------------+
| 2010-03-27 13:23:52 |        0 | 2010-03-27 13:23:54 |
+---------------------+----------+---------------------+

With precision:

SELECT SYSDATE(4);
+--------------------------+
| SYSDATE(4)               |
+--------------------------+
| 2018-07-10 10:17:13.1689 |
+--------------------------+

See Also

1.2.3.46 TIME Function

Syntax

TIME(expr)

Description

Extracts the time part of the time or datetime expression expr and returns it as a string.

Examples

SELECT TIME('2003-12-31 01:02:03');
+-----------------------------+
| TIME('2003-12-31 01:02:03') |
+-----------------------------+
| 01:02:03                    |
+-----------------------------+

SELECT TIME('2003-12-31 01:02:03.000123');
+------------------------------------+
| TIME('2003-12-31 01:02:03.000123') |
+------------------------------------+
| 01:02:03.000123                    |
+------------------------------------+

1.2.3.47 TIMEDIFF

Syntax

TIMEDIFF(expr1,expr2)

Description

TIMEDIFF() returns expr1 - expr2 expressed as a time value. expr1 and expr2 are time or date-and-time expressions, but both must be of the same type.

Examples

SELECT TIMEDIFF('2000:01:01 00:00:00', '2000:01:01 00:00:00.000001');
+---------------------------------------------------------------+
| TIMEDIFF('2000:01:01 00:00:00', '2000:01:01 00:00:00.000001') |
+---------------------------------------------------------------+
| -00:00:00.000001                                              |
+---------------------------------------------------------------+

SELECT TIMEDIFF('2008-12-31 23:59:59.000001', '2008-12-30 01:01:01.000002');
+----------------------------------------------------------------------+
| TIMEDIFF('2008-12-31 23:59:59.000001', '2008-12-30 01:01:01.000002') |
+----------------------------------------------------------------------+
| 46:58:57.999999                                                      |
+----------------------------------------------------------------------+

1.2.3.48 TIMESTAMP FUNCTION

Syntax

TIMESTAMP(expr), TIMESTAMP(expr1,expr2)

Description

With a single argument, this function returns the date or datetime expression expr as a datetime value. With two arguments, it adds the time expression expr2 to the date or datetime expression expr1 and returns the result as a datetime value.

Examples

SELECT TIMESTAMP('2003-12-31');
+-------------------------+
| TIMESTAMP('2003-12-31') |
+-------------------------+
| 2003-12-31 00:00:00     |
+-------------------------+

SELECT TIMESTAMP('2003-12-31 12:00:00','6:30:00');
+--------------------------------------------+
| TIMESTAMP('2003-12-31 12:00:00','6:30:00') |
+--------------------------------------------+
| 2003-12-31 18:30:00                        |
+--------------------------------------------+

1.2.3.49 TIMESTAMPADD

Syntax

TIMESTAMPADD(unit,interval,datetime_expr)

Description

Adds the integer expression interval to the date or datetime expression datetime_expr. The unit for interval is given by the unit argument, which should be one of the following values: MICROSECOND, SECOND, MINUTE, HOUR, DAY, WEEK, MONTH, QUARTER, or YEAR.

The unit value may be specified using one of keywords as shown, or with a prefix of SQL_TSI_. For example, DAY and SQL_TSI_DAY both are legal.

Before MariaDB 5.5, FRAC_SECOND was permitted as a synonym for MICROSECOND.

Examples

SELECT TIMESTAMPADD(MINUTE,1,'2003-01-02');
+-------------------------------------+
| TIMESTAMPADD(MINUTE,1,'2003-01-02') |
+-------------------------------------+
| 2003-01-02 00:01:00                 |
+-------------------------------------+

SELECT TIMESTAMPADD(WEEK,1,'2003-01-02');
+-----------------------------------+
| TIMESTAMPADD(WEEK,1,'2003-01-02') |
+-----------------------------------+
| 2003-01-09                        |
+-----------------------------------+

1.2.3.50 TIMESTAMPDIFF

Syntax

TIMESTAMPDIFF(unit,datetime_expr1,datetime_expr2)

Description

Returns datetime_expr2 - datetime_expr1, where datetime_expr1 and datetime_expr2 are date or datetime expressions. One expression may be a date and the other a datetime; a date value is treated as a datetime having the time part '00:00:00' where necessary. The unit for the result (an integer) is given by the unit argument. The legal values for unit are the same as those listed in the description of the TIMESTAMPADD() function, i.e MICROSECOND, SECOND, MINUTE, HOUR, DAY, WEEK, MONTH, QUARTER, or YEAR.

TIMESTAMPDIFF can also be used to calculate age.

Examples

SELECT TIMESTAMPDIFF(MONTH,'2003-02-01','2003-05-01');
+------------------------------------------------+
| TIMESTAMPDIFF(MONTH,'2003-02-01','2003-05-01') |
+------------------------------------------------+
|                                              3 |
+------------------------------------------------+

SELECT TIMESTAMPDIFF(YEAR,'2002-05-01','2001-01-01');
+-----------------------------------------------+
| TIMESTAMPDIFF(YEAR,'2002-05-01','2001-01-01') |
+-----------------------------------------------+
|                                            -1 |
+-----------------------------------------------+

SELECT TIMESTAMPDIFF(MINUTE,'2003-02-01','2003-05-01 12:05:55');
+----------------------------------------------------------+
| TIMESTAMPDIFF(MINUTE,'2003-02-01','2003-05-01 12:05:55') |
+----------------------------------------------------------+
|                                                   128885 |
+----------------------------------------------------------+

Calculating age:

SELECT CURDATE();
+------------+
| CURDATE()  |
+------------+
| 2019-05-27 |
+------------+

SELECT TIMESTAMPDIFF(YEAR, '1971-06-06', CURDATE()) AS age;
+------+
| age  |
+------+
|   47 |
+------+

SELECT TIMESTAMPDIFF(YEAR, '1971-05-06', CURDATE()) AS age;
+------+
| age  |
+------+
|   48 |
+------+

Age as of 2014-08-02:

SELECT name, date_of_birth, TIMESTAMPDIFF(YEAR,date_of_birth,'2014-08-02') AS age 
  FROM student_details;
+---------+---------------+------+
| name    | date_of_birth | age  |
+---------+---------------+------+
| Chun    | 1993-12-31    |   20 |
| Esben   | 1946-01-01    |   68 |
| Kaolin  | 1996-07-16    |   18 |
| Tatiana | 1988-04-13    |   26 |
+---------+---------------+------+

1.2.3.51 TIME_FORMAT

Syntax

TIME_FORMAT(time,format)

Description

This is used like the DATE_FORMAT() function, but the format string may contain format specifiers only for hours, minutes, and seconds. Other specifiers produce a NULL value or 0.

Examples

SELECT TIME_FORMAT('100:00:00', '%H %k %h %I %l');
+--------------------------------------------+
| TIME_FORMAT('100:00:00', '%H %k %h %I %l') |
+--------------------------------------------+
| 100 100 04 04 4                            |
+--------------------------------------------+

1.2.3.52 TIME_TO_SEC

Syntax

TIME_TO_SEC(time)

Description

Returns the time argument, converted to seconds.

The value returned by TIME_TO_SEC is of type DOUBLE. Before MariaDB 5.3 (and MySQL 5.6), the type was INT. The returned value preserves microseconds of the argument. See also Microseconds in MariaDB.

Examples

SELECT TIME_TO_SEC('22:23:00');
+-------------------------+
| TIME_TO_SEC('22:23:00') |
+-------------------------+
|                   80580 |
+-------------------------+

SELECT TIME_TO_SEC('00:39:38');
+-------------------------+
| TIME_TO_SEC('00:39:38') |
+-------------------------+
|                    2378 |
+-------------------------+

SELECT TIME_TO_SEC('09:12:55.2355');
+------------------------------+
| TIME_TO_SEC('09:12:55.2355') |
+------------------------------+
|                   33175.2355 |
+------------------------------+
1 row in set (0.000 sec)

1.2.3.53 TO_DAYS

Syntax

TO_DAYS(date)

Description

Given a date date, returns the number of days since the start of the current calendar (0000-00-00).

The function is not designed for use with dates before the advent of the Gregorian calendar in October 1582. Results will not be reliable since it doesn't account for the lost days when the calendar changed from the Julian calendar.

This is the converse of the FROM_DAYS() function.

Examples

SELECT TO_DAYS('2007-10-07');
+-----------------------+
| TO_DAYS('2007-10-07') |
+-----------------------+
|                733321 |
+-----------------------+

SELECT TO_DAYS('0000-01-01');
+-----------------------+
| TO_DAYS('0000-01-01') |
+-----------------------+
|                     1 |
+-----------------------+

SELECT TO_DAYS(950501);
+-----------------+
| TO_DAYS(950501) |
+-----------------+
|          728779 |
+-----------------+

1.2.3.54 TO_SECONDS

Syntax

TO_SECONDS(expr)

Description

Returns the number of seconds from year 0 till expr, or NULL if expr is not a valid date or datetime.

Examples

SELECT TO_SECONDS('2013-06-13');
+--------------------------+
| TO_SECONDS('2013-06-13') |
+--------------------------+
|              63538300800 |
+--------------------------+

SELECT TO_SECONDS('2013-06-13 21:45:13');
+-----------------------------------+
| TO_SECONDS('2013-06-13 21:45:13') |
+-----------------------------------+
|                       63538379113 |
+-----------------------------------+

SELECT TO_SECONDS(NOW());
+-------------------+
| TO_SECONDS(NOW()) |
+-------------------+
|       63543530875 |
+-------------------+

SELECT TO_SECONDS(20130513);
+----------------------+
| TO_SECONDS(20130513) |
+----------------------+
|          63535622400 |
+----------------------+
1 row in set (0.00 sec)

SELECT TO_SECONDS(130513);
+--------------------+
| TO_SECONDS(130513) |
+--------------------+
|        63535622400 |
+--------------------+

1.2.3.55 UNIX_TIMESTAMP

Contents

  1. Syntax
  2. Description
    1. Error Handling
    2. Compatibility
  3. Examples
  4. See Also

Syntax

UNIX_TIMESTAMP()
UNIX_TIMESTAMP(date)

Description

If called with no argument, returns a Unix timestamp (seconds since '1970-01-01 00:00:00' UTC) as an unsigned integer. If UNIX_TIMESTAMP() is called with a date argument, it returns the value of the argument as seconds since '1970-01-01 00:00:00' UTC. date may be a DATE string, a DATETIME string, a TIMESTAMP, or a number in the format YYMMDD or YYYYMMDD. The server interprets date as a value in the current time zone and converts it to an internal value in UTC. Clients can set their time zone as described in time zones.

The inverse function of UNIX_TIMESTAMP() is FROM_UNIXTIME()

UNIX_TIMESTAMP() supports microseconds.

Timestamps in MariaDB have a maximum value of 2147483647, equivalent to 2038-01-19 05:14:07. This is due to the underlying 32-bit limitation. Using the function on a date beyond this will result in NULL being returned. Use DATETIME as a storage type if you require dates beyond this.

Error Handling

Returns NULL for wrong arguments to UNIX_TIMESTAMP(). In MySQL and MariaDB before 5.3 wrong arguments to UNIX_TIMESTAMP() returned 0.

Compatibility

As you can see in the examples above, UNIX_TIMESTAMP(constant-date-string) returns a timestamp with 6 decimals while MariaDB 5.2 and before returns it without decimals. This can cause a problem if you are using UNIX_TIMESTAMP() as a partitioning function. You can fix this by using FLOOR(UNIX_TIMESTAMP(..)) or changing the date string to a date number, like 20080101000000.

Examples

SELECT UNIX_TIMESTAMP();
+------------------+
| UNIX_TIMESTAMP() |
+------------------+
|       1269711082 |
+------------------+

SELECT UNIX_TIMESTAMP('2007-11-30 10:30:19');
+---------------------------------------+
| UNIX_TIMESTAMP('2007-11-30 10:30:19') |
+---------------------------------------+
|                     1196436619.000000 |
+---------------------------------------+

SELECT UNIX_TIMESTAMP("2007-11-30 10:30:19.123456");
+----------------------------------------------+
| unix_timestamp("2007-11-30 10:30:19.123456") |
+----------------------------------------------+
|                            1196411419.123456 |
+----------------------------------------------+

SELECT FROM_UNIXTIME(UNIX_TIMESTAMP('2007-11-30 10:30:19'));
+------------------------------------------------------+
| FROM_UNIXTIME(UNIX_TIMESTAMP('2007-11-30 10:30:19')) |
+------------------------------------------------------+
| 2007-11-30 10:30:19.000000                           |
+------------------------------------------------------+

SELECT FROM_UNIXTIME(FLOOR(UNIX_TIMESTAMP('2007-11-30 10:30:19')));
+-------------------------------------------------------------+
| FROM_UNIXTIME(FLOOR(UNIX_TIMESTAMP('2007-11-30 10:30:19'))) |
+-------------------------------------------------------------+
| 2007-11-30 10:30:19                                         |
+-------------------------------------------------------------+

See Also

1.2.3.56 UTC_DATE

Syntax

UTC_DATE, UTC_DATE()

Description

Returns the current UTC date as a value in 'YYYY-MM-DD' or YYYYMMDD format, depending on whether the function is used in a string or numeric context.

Examples

SELECT UTC_DATE(), UTC_DATE() + 0;
+------------+----------------+
| UTC_DATE() | UTC_DATE() + 0 |
+------------+----------------+
| 2010-03-27 |       20100327 |
+------------+----------------+

1.2.3.57 UTC_TIME

Syntax

UTC_TIME
UTC_TIME([precision])

Description

Returns the current UTC time as a value in 'HH:MM:SS' or HHMMSS.uuuuuu format, depending on whether the function is used in a string or numeric context.

The optional precision determines the microsecond precision. See Microseconds in MariaDB.

Examples

SELECT UTC_TIME(), UTC_TIME() + 0;
+------------+----------------+
| UTC_TIME() | UTC_TIME() + 0 |
+------------+----------------+
| 17:32:34   |  173234.000000 |
+------------+----------------+

With precision:

SELECT UTC_TIME(5);
+----------------+
| UTC_TIME(5)    |
+----------------+
| 07:52:50.78369 |
+----------------+

See Also

1.2.3.58 UTC_TIMESTAMP

Syntax

UTC_TIMESTAMP
UTC_TIMESTAMP([precision])

Description

Returns the current UTC date and time as a value in 'YYYY-MM-DD HH:MM:SS' or YYYYMMDDHHMMSS.uuuuuu format, depending on whether the function is used in a string or numeric context.

The optional precision determines the microsecond precision. See Microseconds in MariaDB.

Examples

SELECT UTC_TIMESTAMP(), UTC_TIMESTAMP() + 0;
+---------------------+-----------------------+
| UTC_TIMESTAMP()     | UTC_TIMESTAMP() + 0   |
+---------------------+-----------------------+
| 2010-03-27 17:33:16 | 20100327173316.000000 |
+---------------------+-----------------------+

With precision:

SELECT UTC_TIMESTAMP(4);
+--------------------------+
| UTC_TIMESTAMP(4)         |
+--------------------------+
| 2018-07-10 07:51:09.1019 |
+--------------------------+

See Also

1.2.3.59 WEEK

Syntax

WEEK(date[,mode])

Description

This function returns the week number for date. The two-argument form of WEEK() allows you to specify whether the week starts on Sunday or Monday and whether the return value should be in the range from 0 to 53 or from 1 to 53. If the mode argument is omitted, the value of the default_week_format system variable is used.

Modes

Mode1st day of weekRangeWeek 1 is the 1st week with
0Sunday0-53a Sunday in this year
1Monday0-53more than 3 days this year
2Sunday1-53a Sunday in this year
3Monday1-53more than 3 days this year
4Sunday0-53more than 3 days this year
5Monday0-53a Monday in this year
6Sunday1-53more than 3 days this year
7Monday1-53a Monday in this year

With the mode value of 3, which means “more than 3 days this year”, weeks are numbered according to ISO 8601:1988.

Examples

SELECT WEEK('2008-02-20');
+--------------------+
| WEEK('2008-02-20') |
+--------------------+
|                  7 |
+--------------------+

SELECT WEEK('2008-02-20',0);
+----------------------+
| WEEK('2008-02-20',0) |
+----------------------+
|                    7 |
+----------------------+

SELECT WEEK('2008-02-20',1);
+----------------------+
| WEEK('2008-02-20',1) |
+----------------------+
|                    8 |
+----------------------+

SELECT WEEK('2008-12-31',0);
+----------------------+
| WEEK('2008-12-31',0) |
+----------------------+
|                   52 |
+----------------------+

SELECT WEEK('2008-12-31',1);
+----------------------+
| WEEK('2008-12-31',1) |
+----------------------+
|                   53 |
+----------------------+

 SELECT WEEK('2019-12-30',3);
+----------------------+
| WEEK('2019-12-30',3) |
+----------------------+
|                    1 |
+----------------------+

CREATE TABLE t1 (d DATETIME);
INSERT INTO t1 VALUES
    ("2007-01-30 21:31:07"),
    ("1983-10-15 06:42:51"),
    ("2011-04-21 12:34:56"),
    ("2011-10-30 06:31:41"),
    ("2011-01-30 14:03:25"),
    ("2004-10-07 11:19:34");

SELECT d, WEEK(d,0), WEEK(d,1) from t1;
+---------------------+-----------+-----------+
| d                   | WEEK(d,0) | WEEK(d,1) |
+---------------------+-----------+-----------+
| 2007-01-30 21:31:07 |         4 |         5 |
| 1983-10-15 06:42:51 |        41 |        41 |
| 2011-04-21 12:34:56 |        16 |        16 |
| 2011-10-30 06:31:41 |        44 |        43 |
| 2011-01-30 14:03:25 |         5 |         4 |
| 2004-10-07 11:19:34 |        40 |        41 |
+---------------------+-----------+-----------+

1.2.3.60 WEEKDAY

Syntax

WEEKDAY(date)

Description

Returns the weekday index for date (0 = Monday, 1 = Tuesday, ... 6 = Sunday).

This contrasts with DAYOFWEEK() which follows the ODBC standard (1 = Sunday, 2 = Monday, ..., 7 = Saturday).

Examples

SELECT WEEKDAY('2008-02-03 22:23:00');
+--------------------------------+
| WEEKDAY('2008-02-03 22:23:00') |
+--------------------------------+
|                              6 |
+--------------------------------+

SELECT WEEKDAY('2007-11-06');
+-----------------------+
| WEEKDAY('2007-11-06') |
+-----------------------+
|                     1 |
+-----------------------+

CREATE TABLE t1 (d DATETIME);
INSERT INTO t1 VALUES
    ("2007-01-30 21:31:07"),
    ("1983-10-15 06:42:51"),
    ("2011-04-21 12:34:56"),
    ("2011-10-30 06:31:41"),
    ("2011-01-30 14:03:25"),
    ("2004-10-07 11:19:34");

SELECT d FROM t1 where WEEKDAY(d) = 6;
+---------------------+
| d                   |
+---------------------+
| 2011-10-30 06:31:41 |
| 2011-01-30 14:03:25 |
+---------------------+

1.2.3.61 WEEKOFYEAR

Syntax

WEEKOFYEAR(date)

Description

Returns the calendar week of the date as a number in the range from 1 to 53. WEEKOFYEAR() is a compatibility function that is equivalent to WEEK(date,3).

Examples

SELECT WEEKOFYEAR('2008-02-20');
+--------------------------+
| WEEKOFYEAR('2008-02-20') |
+--------------------------+
|                        8 |
+--------------------------+

CREATE TABLE t1 (d DATETIME);
INSERT INTO t1 VALUES
    ("2007-01-30 21:31:07"),
    ("1983-10-15 06:42:51"),
    ("2011-04-21 12:34:56"),
    ("2011-10-30 06:31:41"),
    ("2011-01-30 14:03:25"),
    ("2004-10-07 11:19:34");

 select * from t1;
+---------------------+
| d                   |
+---------------------+
| 2007-01-30 21:31:07 |
| 1983-10-15 06:42:51 |
| 2011-04-21 12:34:56 |
| 2011-10-30 06:31:41 |
| 2011-01-30 14:03:25 |
| 2004-10-07 11:19:34 |
+---------------------+

SELECT d, WEEKOFYEAR(d), WEEK(d,3) from t1;
+---------------------+---------------+-----------+
| d                   | WEEKOFYEAR(d) | WEEK(d,3) |
+---------------------+---------------+-----------+
| 2007-01-30 21:31:07 |             5 |         5 |
| 1983-10-15 06:42:51 |            41 |        41 |
| 2011-04-21 12:34:56 |            16 |        16 |
| 2011-10-30 06:31:41 |            43 |        43 |
| 2011-01-30 14:03:25 |             4 |         4 |
| 2004-10-07 11:19:34 |            41 |        41 |
+---------------------+---------------+-----------+

1.2.3.62 YEAR

Syntax

YEAR(date)

Description

Returns the year for the given date, in the range 1000 to 9999, or 0 for the "zero" date.

Examples

CREATE TABLE t1 (d DATETIME);
INSERT INTO t1 VALUES
    ("2007-01-30 21:31:07"),
    ("1983-10-15 06:42:51"),
    ("2011-04-21 12:34:56"),
    ("2011-10-30 06:31:41"),
    ("2011-01-30 14:03:25"),
    ("2004-10-07 11:19:34");

SELECT * FROM t1;
+---------------------+
| d                   |
+---------------------+
| 2007-01-30 21:31:07 |
| 1983-10-15 06:42:51 |
| 2011-04-21 12:34:56 |
| 2011-10-30 06:31:41 |
| 2011-01-30 14:03:25 |
| 2004-10-07 11:19:34 |
+---------------------+

SELECT * FROM t1 WHERE YEAR(d) = 2011;
+---------------------+
| d                   |
+---------------------+
| 2011-04-21 12:34:56 |
| 2011-10-30 06:31:41 |
| 2011-01-30 14:03:25 |
+---------------------+

SELECT YEAR('1987-01-01');
+--------------------+
| YEAR('1987-01-01') |
+--------------------+
|               1987 |
+--------------------+

See Also

1.2.3.63 YEARWEEK

Syntax

YEARWEEK(date), YEARWEEK(date,mode)

Description

Returns year and week for a date. The mode argument works exactly like the mode argument to WEEK(). The year in the result may be different from the year in the date argument for the first and the last week of the year.

Examples

SELECT YEARWEEK('1987-01-01');
+------------------------+
| YEARWEEK('1987-01-01') |
+------------------------+
|                 198652 |
+------------------------+

CREATE TABLE t1 (d DATETIME);
INSERT INTO t1 VALUES
    ("2007-01-30 21:31:07"),
    ("1983-10-15 06:42:51"),
    ("2011-04-21 12:34:56"),
    ("2011-10-30 06:31:41"),
    ("2011-01-30 14:03:25"),
    ("2004-10-07 11:19:34");

SELECT * FROM t1;
+---------------------+
| d                   |
+---------------------+
| 2007-01-30 21:31:07 |
| 1983-10-15 06:42:51 |
| 2011-04-21 12:34:56 |
| 2011-10-30 06:31:41 |
| 2011-01-30 14:03:25 |
| 2004-10-07 11:19:34 |
+---------------------+
6 rows in set (0.02 sec)

SELECT YEARWEEK(d) FROM t1 WHERE YEAR(d) = 2011;
+-------------+
| YEARWEEK(d) |
+-------------+
|      201116 |
|      201144 |
|      201105 |
+-------------+
3 rows in set (0.03 sec)

1.2.4 Aggregate Functions

The following functions (also called aggregate functions) can be used with the GROUP BY clause:

1.2.4.1 Stored Aggregate Functions

MariaDB starting with 10.3.3

The ability to create stored aggregate functions was added in MariaDB 10.3.3.

Contents

  1. Standard Syntax
    1. Using SQL/PL
  2. Examples
    1. SQL/PL Example
  3. See Also

Aggregate functions are functions that are computed over a sequence of rows and return one result for the sequence of rows.

Creating a custom aggregate function is done using the CREATE FUNCTION statement with two main differences:

  • The addition of the AGGREGATE keyword, so CREATE AGGREGATE FUNCTION
  • The FETCH GROUP NEXT ROW instruction inside the loop
  • Oracle PL/SQL compatibility using SQL/PL is provided

Standard Syntax

CREATE AGGREGATE FUNCTION function_name (parameters) RETURNS return_type
BEGIN
      All types of declarations
      DECLARE CONTINUE HANDLER FOR NOT FOUND RETURN return_val;
      LOOP
           FETCH GROUP NEXT ROW; // fetches next row from table
           other instructions
      END LOOP;
END

Stored aggregate functions were a 2016 Google Summer of Code project by Varun Gupta.

Using SQL/PL

SET sql_mode=Oracle;
DELIMITER //

CREATE AGGREGATE FUNCTION function_name (parameters) RETURN return_type
   declarations
BEGIN
   LOOP
      FETCH GROUP NEXT ROW; -- fetches next row from table
      -- other instructions

   END LOOP;
EXCEPTION
   WHEN NO_DATA_FOUND THEN
      RETURN return_val;
END //

DELIMITER ;

Examples

First a simplified example:

CREATE TABLE marks(stud_id INT, grade_count INT);

INSERT INTO marks VALUES (1,6), (2,4), (3,7), (4,5), (5,8);

SELECT * FROM marks;
+---------+-------------+
| stud_id | grade_count |
+---------+-------------+
|       1 |           6 |
|       2 |           4 |
|       3 |           7 |
|       4 |           5 |
|       5 |           8 |
+---------+-------------+

DELIMITER //
CREATE AGGREGATE FUNCTION IF NOT EXISTS aggregate_count(x INT) RETURNS INT
BEGIN
 DECLARE count_students INT DEFAULT 0;
 DECLARE CONTINUE HANDLER FOR NOT FOUND
 RETURN count_students;
      LOOP
          FETCH GROUP NEXT ROW;
          IF x  THEN
            SET count_students = count_students+1;
          END IF;
      END LOOP;
END //
DELIMITER ;

A non-trivial example that cannot easily be rewritten using existing functions:

DELIMITER //
CREATE AGGREGATE FUNCTION medi_int(x INT) RETURNS DOUBLE
BEGIN
  DECLARE CONTINUE HANDLER FOR NOT FOUND
    BEGIN
      DECLARE res DOUBLE;
      DECLARE cnt INT DEFAULT (SELECT COUNT(*) FROM tt);
      DECLARE lim INT DEFAULT (cnt-1) DIV 2;
      IF cnt % 2 = 0 THEN
        SET res = (SELECT AVG(a) FROM (SELECT a FROM tt ORDER BY a LIMIT lim,2) ttt);
      ELSE
        SET res = (SELECT a FROM tt ORDER BY a LIMIT lim,1);
      END IF;
      DROP TEMPORARY TABLE tt;
      RETURN res;
    END;
  CREATE TEMPORARY TABLE tt (a INT);
  LOOP
    FETCH GROUP NEXT ROW;
    INSERT INTO tt VALUES (x);
  END LOOP;
END //
DELIMITER ;

SQL/PL Example

This uses the same marks table as created above.

SET sql_mode=Oracle;
DELIMITER //

CREATE AGGREGATE FUNCTION aggregate_count(x INT) RETURN INT AS count_students INT DEFAULT 0;
BEGIN
   LOOP
      FETCH GROUP NEXT ROW;
      IF x  THEN
        SET count_students := count_students+1;
      END IF;
   END LOOP;
EXCEPTION
   WHEN NO_DATA_FOUND THEN
      RETURN count_students;
END aggregate_count //
DELIMITER ;

SELECT aggregate_count(stud_id) FROM marks;

See Also

1.2.4.2 AVG

Syntax

AVG([DISTINCT] expr)

Contents

  1. Syntax
  2. Description
  3. Examples
  4. See Also

Description

Returns the average value of expr. The DISTINCT option can be used to return the average of the distinct values of expr. NULL values are ignored. It is an aggregate function, and so can be used with the GROUP BY clause.

AVG() returns NULL if there were no matching rows.

From MariaDB 10.2.0, AVG() can be used as a window function.

Examples

CREATE TABLE sales (sales_value INT);

INSERT INTO sales VALUES(10),(20),(20),(40);

SELECT AVG(sales_value) FROM sales;
+------------------+
| AVG(sales_value) |
+------------------+
|          22.5000 |
+------------------+

SELECT AVG(DISTINCT(sales_value)) FROM sales;
+----------------------------+
| AVG(DISTINCT(sales_value)) |
+----------------------------+
|                    23.3333 |
+----------------------------+

Commonly, AVG() is used with a GROUP BY clause:

CREATE TABLE student (name CHAR(10), test CHAR(10), score TINYINT); 

INSERT INTO student VALUES 
  ('Chun', 'SQL', 75), ('Chun', 'Tuning', 73), 
  ('Esben', 'SQL', 43), ('Esben', 'Tuning', 31), 
  ('Kaolin', 'SQL', 56), ('Kaolin', 'Tuning', 88), 
  ('Tatiana', 'SQL', 87), ('Tatiana', 'Tuning', 83);

SELECT name, AVG(score) FROM student GROUP BY name;
+---------+------------+
| name    | AVG(score) |
+---------+------------+
| Chun    |    74.0000 |
| Esben   |    37.0000 |
| Kaolin  |    72.0000 |
| Tatiana |    85.0000 |
+---------+------------+

Be careful to avoid this common mistake, not grouping correctly and returning mismatched data: 

SELECT name,test,AVG(score) FROM student;
+------+------+------------+
| name | test | MIN(score) |
+------+------+------------+
| Chun | SQL  |         31 |
+------+------+------------+

As a window function:

CREATE TABLE student_test (name CHAR(10), test CHAR(10), score TINYINT); 

INSERT INTO student_test VALUES 
    ('Chun', 'SQL', 75), ('Chun', 'Tuning', 73), 
    ('Esben', 'SQL', 43), ('Esben', 'Tuning', 31), 
    ('Kaolin', 'SQL', 56), ('Kaolin', 'Tuning', 88), 
    ('Tatiana', 'SQL', 87), ('Tatiana', 'Tuning', 83);

SELECT name, test, score, AVG(score) OVER (PARTITION BY test) 
    AS average_by_test FROM student_test;
+---------+--------+-------+-----------------+
| name    | test   | score | average_by_test |
+---------+--------+-------+-----------------+
| Chun    | SQL    |    75 |         65.2500 |
| Chun    | Tuning |    73 |         68.7500 |
| Esben   | SQL    |    43 |         65.2500 |
| Esben   | Tuning |    31 |         68.7500 |
| Kaolin  | SQL    |    56 |         65.2500 |
| Kaolin  | Tuning |    88 |         68.7500 |
| Tatiana | SQL    |    87 |         65.2500 |
| Tatiana | Tuning |    83 |         68.7500 |
+---------+--------+-------+-----------------+

See Also

1.2.4.3 BIT_AND

Syntax

BIT_AND(expr) [over_clause]

Description

Returns the bitwise AND of all bits in expr. The calculation is performed with 64-bit (BIGINT) precision. It is an aggregate function, and so can be used with the GROUP BY clause.

If no rows match, BIT_AND will return a value with all bits set to 1. NULL values have no effect on the result unless all results are NULL, which is treated as no match.

From MariaDB 10.2.0, BIT_AND can be used as a window function with the addition of the over_clause.

Examples

CREATE TABLE vals (x INT);

INSERT INTO vals VALUES(111),(110),(100);

SELECT BIT_AND(x), BIT_OR(x), BIT_XOR(x) FROM vals;
+------------+-----------+------------+
| BIT_AND(x) | BIT_OR(x) | BIT_XOR(x) |
+------------+-----------+------------+
|        100 |       111 |        101 |
+------------+-----------+------------+

As an aggregate function:

CREATE TABLE vals2 (category VARCHAR(1), x INT);

INSERT INTO vals2 VALUES
  ('a',111),('a',110),('a',100),
  ('b','000'),('b',001),('b',011);

SELECT category, BIT_AND(x), BIT_OR(x), BIT_XOR(x) 
  FROM vals GROUP BY category;
+----------+------------+-----------+------------+
| category | BIT_AND(x) | BIT_OR(x) | BIT_XOR(x) |
+----------+------------+-----------+------------+
| a        |        100 |       111 |        101 |
| b        |          0 |        11 |         10 |
+----------+------------+-----------+------------+

No match:

SELECT BIT_AND(NULL);
+----------------------+
| BIT_AND(NULL)        |
+----------------------+
| 18446744073709551615 |
+----------------------+

See Also

1.2.4.4 BIT_OR

Syntax

BIT_OR(expr) [over_clause]

Contents

  1. Syntax
  2. Description
  3. Examples
  4. See Also

Description

Returns the bitwise OR of all bits in expr. The calculation is performed with 64-bit (BIGINT) precision. It is an aggregate function, and so can be used with the GROUP BY clause.

If no rows match, BIT_OR will return a value with all bits set to 0. NULL values have no effect on the result unless all results are NULL, which is treated as no match.

From MariaDB 10.2.0, BIT_OR can be used as a window function with the addition of the over_clause.

Examples

CREATE TABLE vals (x INT);

INSERT INTO vals VALUES(111),(110),(100);

SELECT BIT_AND(x), BIT_OR(x), BIT_XOR(x) FROM vals;
+------------+-----------+------------+
| BIT_AND(x) | BIT_OR(x) | BIT_XOR(x) |
+------------+-----------+------------+
|        100 |       111 |        101 |
+------------+-----------+------------+

As an aggregate function:

CREATE TABLE vals2 (category VARCHAR(1), x INT);

INSERT INTO vals2 VALUES
  ('a',111),('a',110),('a',100),
  ('b','000'),('b',001),('b',011);

SELECT category, BIT_AND(x), BIT_OR(x), BIT_XOR(x) 
  FROM vals GROUP BY category;
+----------+------------+-----------+------------+
| category | BIT_AND(x) | BIT_OR(x) | BIT_XOR(x) |
+----------+------------+-----------+------------+
| a        |        100 |       111 |        101 |
| b        |          0 |        11 |         10 |
+----------+------------+-----------+------------+

No match:

SELECT BIT_OR(NULL);
+--------------+
| BIT_OR(NULL) |
+--------------+
|            0 |
+--------------+

See Also

1.2.4.5 BIT_XOR

Syntax

BIT_XOR(expr) [over_clause]

Contents

  1. Syntax
  2. Description
  3. Examples
  4. See Also

Description

Returns the bitwise XOR of all bits in expr. The calculation is performed with 64-bit (BIGINT) precision. It is an aggregate function, and so can be used with the GROUP BY clause.

If no rows match, BIT_XOR will return a value with all bits set to 0. NULL values have no effect on the result unless all results are NULL, which is treated as no match.

From MariaDB 10.2.0, BIT_XOR can be used as a window function with the addition of the over_clause.

Examples

CREATE TABLE vals (x INT);

INSERT INTO vals VALUES(111),(110),(100);

SELECT BIT_AND(x), BIT_OR(x), BIT_XOR(x) FROM vals;
+------------+-----------+------------+
| BIT_AND(x) | BIT_OR(x) | BIT_XOR(x) |
+------------+-----------+------------+
|        100 |       111 |        101 |
+------------+-----------+------------+

As an aggregate function:

CREATE TABLE vals2 (category VARCHAR(1), x INT);

INSERT INTO vals2 VALUES
  ('a',111),('a',110),('a',100),
  ('b','000'),('b',001),('b',011);

SELECT category, BIT_AND(x), BIT_OR(x), BIT_XOR(x) 
  FROM vals GROUP BY category;
+----------+------------+-----------+------------+
| category | BIT_AND(x) | BIT_OR(x) | BIT_XOR(x) |
+----------+------------+-----------+------------+
| a        |        100 |       111 |        101 |
| b        |          0 |        11 |         10 |
+----------+------------+-----------+------------+

No match:

SELECT BIT_XOR(NULL);
+---------------+
| BIT_XOR(NULL) |
+---------------+
|             0 |
+---------------+

See Also

1.2.4.6 COUNT

Syntax

COUNT(expr)

Contents

  1. Syntax
  2. Description
  3. Examples
  4. See Also

Description

Returns a count of the number of non-NULL values of expr in the rows retrieved by a SELECT statement. The result is a BIGINT value. It is an aggregate function, and so can be used with the GROUP BY clause.

COUNT(*) counts the total number of rows in a table.

COUNT() returns 0 if there were no matching rows.

From MariaDB 10.2.0, COUNT() can be used as a window function.

Examples

CREATE TABLE student (name CHAR(10), test CHAR(10), score TINYINT); 

INSERT INTO student VALUES 
  ('Chun', 'SQL', 75), ('Chun', 'Tuning', 73), 
  ('Esben', 'SQL', 43), ('Esben', 'Tuning', 31), 
  ('Kaolin', 'SQL', 56), ('Kaolin', 'Tuning', 88), 
  ('Tatiana', 'SQL', 87), ('Tatiana', 'Tuning', 83);

SELECT COUNT(*) FROM student;
+----------+
| COUNT(*) |
+----------+
|        8 |
+----------+

COUNT(DISTINCT) example:

SELECT COUNT(DISTINCT (name)) FROM student;
+------------------------+
| COUNT(DISTINCT (name)) |
+------------------------+
|                      4 |
+------------------------+

As a window function

CREATE OR REPLACE TABLE student_test (name CHAR(10), test CHAR(10), score TINYINT);

INSERT INTO student_test VALUES 
    ('Chun', 'SQL', 75), ('Chun', 'Tuning', 73), 
    ('Esben', 'SQL', 43), ('Esben', 'Tuning', 31), 
    ('Kaolin', 'SQL', 56), ('Kaolin', 'Tuning', 88), 
    ('Tatiana', 'SQL', 87);

SELECT name, test, score, COUNT(score) OVER (PARTITION BY name) 
    AS tests_written FROM student_test;
+---------+--------+-------+---------------+
| name    | test   | score | tests_written |
+---------+--------+-------+---------------+
| Chun    | SQL    |    75 |             2 |
| Chun    | Tuning |    73 |             2 |
| Esben   | SQL    |    43 |             2 |
| Esben   | Tuning |    31 |             2 |
| Kaolin  | SQL    |    56 |             2 |
| Kaolin  | Tuning |    88 |             2 |
| Tatiana | SQL    |    87 |             1 |
+---------+--------+-------+---------------+

See Also

1.2.4.7 COUNT DISTINCT

Syntax

COUNT(DISTINCT expr,[expr...])

Contents

  1. Syntax
  2. Description
  3. Examples
  4. See Also

Description

Returns a count of the number of different non-NULL values.

COUNT(DISTINCT) returns 0 if there were no matching rows.

Although, from MariaDB 10.2.0, COUNT can be used as a window function, COUNT DISTINCT cannot be.

Examples

CREATE TABLE student (name CHAR(10), test CHAR(10), score TINYINT); 

INSERT INTO student VALUES 
  ('Chun', 'SQL', 75), ('Chun', 'Tuning', 73), 
  ('Esben', 'SQL', 43), ('Esben', 'Tuning', 31), 
  ('Kaolin', 'SQL', 56), ('Kaolin', 'Tuning', 88), 
  ('Tatiana', 'SQL', 87), ('Tatiana', 'Tuning', 83);

SELECT COUNT(*) FROM student;
+----------+
| COUNT(*) |
+----------+
|        8 |
+----------+

SELECT COUNT(DISTINCT (name)) FROM student;
+------------------------+
| COUNT(DISTINCT (name)) |
+------------------------+
|                      4 |
+------------------------+

See Also

1.2.4.8 GROUP_CONCAT

Syntax

GROUP_CONCAT(expr)

Contents

  1. Syntax
  2. Description
    1. LIMIT
  3. Examples
  4. See Also

Description

This function returns a string result with the concatenated non-NULL values from a group. It returns NULL if there are no non-NULL values.

The maximum returned length in bytes is determined by the group_concat_max_len server system variable, which defaults to 1M (>= MariaDB 10.2.4) or 1K (<= MariaDB 10.2.3).

If group_concat_max_len <= 512, the return type is VARBINARY or VARCHAR; otherwise, the return type is BLOB or TEXT. The choice between binary or non-binary types depends from the input.

The full syntax is as follows:

GROUP_CONCAT([DISTINCT] expr [,expr ...]
             [ORDER BY {unsigned_integer | col_name | expr}
                 [ASC | DESC] [,col_name ...]]
             [SEPARATOR str_val]
             [LIMIT {[offset,] row_count | row_count OFFSET offset}])

DISTINCT eliminates duplicate values from the output string.

ORDER BY determines the order of returned values.

SEPARATOR specifies a separator between the values. The default separator is a comma (,). It is possible to avoid using a separator by specifying an empty string.

LIMIT

MariaDB starting with 10.3.3

Until MariaDB 10.3.2, it was not possible to use the LIMIT clause with GROUP_CONCAT. This restriction was lifted in MariaDB 10.3.3.

Examples

SELECT student_name,
       GROUP_CONCAT(test_score)
       FROM student
       GROUP BY student_name;

Get a readable list of MariaDB users from the mysql.user table:

SELECT GROUP_CONCAT(DISTINCT User ORDER BY User SEPARATOR '\n')
   FROM mysql.user;

In the former example, DISTINCT is used because the same user may occur more than once. The new line (\n) used as a SEPARATOR makes the results easier to read.

Get a readable list of hosts from which each user can connect:

SELECT User, GROUP_CONCAT(Host ORDER BY Host SEPARATOR ', ') 
   FROM mysql.user GROUP BY User ORDER BY User;

The former example shows the difference between the GROUP_CONCAT's ORDER BY (which sorts the concatenated hosts), and the SELECT's ORDER BY (which sorts the rows).

From MariaDB 10.3.3, LIMIT can be used with GROUP_CONCAT, so, for example, given the following table:

CREATE TABLE d (dd DATE, cc INT);

INSERT INTO d VALUES ('2017-01-01',1);
INSERT INTO d VALUES ('2017-01-02',2);
INSERT INTO d VALUES ('2017-01-04',3);

the following query:

SELECT SUBSTRING_INDEX(GROUP_CONCAT(CONCAT_WS(":",dd,cc) ORDER BY cc DESC),",",1) FROM d;
+----------------------------------------------------------------------------+
| SUBSTRING_INDEX(GROUP_CONCAT(CONCAT_WS(":",dd,cc) ORDER BY cc DESC),",",1) |
+----------------------------------------------------------------------------+
| 2017-01-04:3                                                               |
+----------------------------------------------------------------------------+

can be more simply rewritten as:

SELECT GROUP_CONCAT(CONCAT_WS(":",dd,cc) ORDER BY cc DESC LIMIT 1) FROM d;
+-------------------------------------------------------------+
| GROUP_CONCAT(CONCAT_WS(":",dd,cc) ORDER BY cc DESC LIMIT 1) |
+-------------------------------------------------------------+
| 2017-01-04:3                                                |
+-------------------------------------------------------------+

See Also

1.2.4.9 JSON_ARRAYAGG

MariaDB starting with 10.5.0

JSON_ARRAYAGG was added in MariaDB 10.5.0.

Syntax

JSON_ARRAYAGG(column_or_expression)

Description

JSON_ARRAYAGG returns a JSON array containing an element for each value in a given set of JSON or SQL values. It acts on a column or an expression that evaluates to a single value.

Returns NULL in the case of an error, or if the result contains no rows.

JSON_ARRAYAGG cannot currently be used as a window function.

The full syntax is as follows:

JSON_ARRAYAGG([DISTINCT] expr [,expr ...]
             [ORDER BY {unsigned_integer | col_name | expr}
                 [ASC | DESC] [,col_name ...]]
             [LIMIT {[offset,] row_count | row_count OFFSET offset}])

Examples

CREATE TABLE t1 (a INT, b INT);

INSERT INTO t1 VALUES (1, 1),(2, 1), (1, 1),(2, 1), (3, 2),(2, 2),(2, 2),(2, 2);

SELECT JSON_ARRAYAGG(a), JSON_ARRAYAGG(b) FROM t1;
+-------------------+-------------------+
| JSON_ARRAYAGG(a)  | JSON_ARRAYAGG(b)  |
+-------------------+-------------------+
| [1,2,1,2,3,2,2,2] | [1,1,1,1,2,2,2,2] |
+-------------------+-------------------+

SELECT JSON_ARRAYAGG(a), JSON_ARRAYAGG(b) FROM t1 GROUP BY b;
+------------------+------------------+
| JSON_ARRAYAGG(a) | JSON_ARRAYAGG(b) |
+------------------+------------------+
| [1,2,1,2]        | [1,1,1,1]        |
| [3,2,2,2]        | [2,2,2,2]        |
+------------------+------------------+

1.2.4.10 JSON_OBJECTAGG

MariaDB starting with 10.5.0

JSON_OBJECTAGG was added in MariaDB 10.5.0.

Syntax

JSON_OBJECTAGG(key, value)

Description

JSON_OBJECTAGG returns a JSON object containing key-value pairs. It takes two expressions that evaluate to a single value, or two column names, as arguments, the first used as a key, and the second as a value.

Returns NULL in the case of an error, or if the result contains no rows.

JSON_OBJECTAGG cannot currently be used as a window function.

Examples

select * from t1;
+------+-------+
| a    | b     |
+------+-------+
|    1 | Hello |
|    1 | World |
|    2 | This  |
+------+-------+

SELECT JSON_OBJECTAGG(a, b) FROM t1;
+----------------------------------------+
| JSON_OBJECTAGG(a, b)                   |
+----------------------------------------+
| {"1":"Hello", "1":"World", "2":"This"} |
+----------------------------------------+

1.2.4.11 MAX

Syntax

MAX([DISTINCT] expr)

Contents

  1. Syntax
  2. Description
  3. Examples
  4. See Also

Description

Returns the largest, or maximum, value of expr. MAX() can also take a string argument in which case it returns the maximum string value. The DISTINCT keyword can be used to find the maximum of the distinct values of expr, however, this produces the same result as omitting DISTINCT.

Note that SET and ENUM fields are currently compared by their string value rather than their relative position in the set, so MAX() may produce a different highest result than ORDER BY DESC.

It is an aggregate function, and so can be used with the GROUP BY clause.

From MariaDB 10.2.2, MAX() can be used as a window function.

MAX() returns NULL if there were no matching rows.

Examples

CREATE TABLE student (name CHAR(10), test CHAR(10), score TINYINT); 

INSERT INTO student VALUES 
  ('Chun', 'SQL', 75), ('Chun', 'Tuning', 73), 
  ('Esben', 'SQL', 43), ('Esben', 'Tuning', 31), 
  ('Kaolin', 'SQL', 56), ('Kaolin', 'Tuning', 88), 
  ('Tatiana', 'SQL', 87), ('Tatiana', 'Tuning', 83);

SELECT name, MAX(score) FROM student GROUP BY name;
+---------+------------+
| name    | MAX(score) |
+---------+------------+
| Chun    |         75 |
| Esben   |         43 |
| Kaolin  |         88 |
| Tatiana |         87 |
+---------+------------+

MAX string:

SELECT MAX(name) FROM student;
+-----------+
| MAX(name) |
+-----------+
| Tatiana   |
+-----------+

Be careful to avoid this common mistake, not grouping correctly and returning mismatched data: 

SELECT name,test,MAX(SCORE) FROM student;
+------+------+------------+
| name | test | MAX(SCORE) |
+------+------+------------+
| Chun | SQL  |         88 |
+------+------+------------+

Difference between ORDER BY DESC and MAX():

CREATE TABLE student2(name CHAR(10),grade ENUM('b','c','a'));

INSERT INTO student2 VALUES('Chun','b'),('Esben','c'),('Kaolin','a');

SELECT MAX(grade) FROM student2;
+------------+
| MAX(grade) |
+------------+
| c          |
+------------+

SELECT grade FROM student2 ORDER BY grade DESC LIMIT 1;
+-------+
| grade |
+-------+
| a     |
+-------+

As a window function:

CREATE OR REPLACE TABLE student_test (name CHAR(10), test CHAR(10), score TINYINT);
INSERT INTO student_test VALUES 
    ('Chun', 'SQL', 75), ('Chun', 'Tuning', 73), 
    ('Esben', 'SQL', 43), ('Esben', 'Tuning', 31), 
    ('Kaolin', 'SQL', 56), ('Kaolin', 'Tuning', 88), 
    ('Tatiana', 'SQL', 87);

SELECT name, test, score, MAX(score) 
  OVER (PARTITION BY name) AS highest_score FROM student_test;
+---------+--------+-------+---------------+
| name    | test   | score | highest_score |
+---------+--------+-------+---------------+
| Chun    | SQL    |    75 |            75 |
| Chun    | Tuning |    73 |            75 |
| Esben   | SQL    |    43 |            43 |
| Esben   | Tuning |    31 |            43 |
| Kaolin  | SQL    |    56 |            88 |
| Kaolin  | Tuning |    88 |            88 |
| Tatiana | SQL    |    87 |            87 |
+---------+--------+-------+---------------+

See Also

1.2.4.12 MIN

Syntax

MIN([DISTINCT] expr)

Contents

  1. Syntax
  2. Description
  3. Examples
  4. See Also

Description

Returns the minimum value of expr. MIN() may take a string argument, in which case it returns the minimum string value. The DISTINCT keyword can be used to find the minimum of the distinct values of expr, however, this produces the same result as omitting DISTINCT.

Note that SET and ENUM fields are currently compared by their string value rather than their relative position in the set, so MIN() may produce a different lowest result than ORDER BY ASC.

It is an aggregate function, and so can be used with the GROUP BY clause.

From MariaDB 10.2.2, MIN() can be used as a window function.

MIN() returns NULL if there were no matching rows.

Examples

CREATE TABLE student (name CHAR(10), test CHAR(10), score TINYINT); 

INSERT INTO student VALUES 
  ('Chun', 'SQL', 75), ('Chun', 'Tuning', 73), 
  ('Esben', 'SQL', 43), ('Esben', 'Tuning', 31), 
  ('Kaolin', 'SQL', 56), ('Kaolin', 'Tuning', 88), 
  ('Tatiana', 'SQL', 87), ('Tatiana', 'Tuning', 83);

SELECT name, MIN(score) FROM student GROUP BY name;
+---------+------------+
| name    | MIN(score) |
+---------+------------+
| Chun    |         73 |
| Esben   |         31 |
| Kaolin  |         56 |
| Tatiana |         83 |
+---------+------------+

MIN() with a string:

SELECT MIN(name) FROM student;
+-----------+
| MIN(name) |
+-----------+
| Chun      |
+-----------+

Be careful to avoid this common mistake, not grouping correctly and returning mismatched data: 

SELECT name,test,MIN(score) FROM student;
+------+------+------------+
| name | test | MIN(score) |
+------+------+------------+
| Chun | SQL  |         31 |
+------+------+------------+

Difference between ORDER BY ASC and MIN():

CREATE TABLE student2(name CHAR(10),grade ENUM('b','c','a'));

INSERT INTO student2 VALUES('Chun','b'),('Esben','c'),('Kaolin','a');

SELECT MIN(grade) FROM student2;
+------------+
| MIN(grade) |
+------------+
| a          |
+------------+

SELECT grade FROM student2 ORDER BY grade ASC LIMIT 1;
+-------+
| grade |
+-------+
| b     |
+-------+

As a window function:

CREATE OR REPLACE TABLE student_test (name CHAR(10), test CHAR(10), score TINYINT);
INSERT INTO student_test VALUES 
    ('Chun', 'SQL', 75), ('Chun', 'Tuning', 73), 
    ('Esben', 'SQL', 43), ('Esben', 'Tuning', 31), 
    ('Kaolin', 'SQL', 56), ('Kaolin', 'Tuning', 88), 
    ('Tatiana', 'SQL', 87);


SELECT name, test, score, MIN(score) 
  OVER (PARTITION BY name) AS lowest_score FROM student_test;
+---------+--------+-------+--------------+
| name    | test   | score | lowest_score |
+---------+--------+-------+--------------+
| Chun    | SQL    |    75 |           73 |
| Chun    | Tuning |    73 |           73 |
| Esben   | SQL    |    43 |           31 |
| Esben   | Tuning |    31 |           31 |
| Kaolin  | SQL    |    56 |           56 |
| Kaolin  | Tuning |    88 |           56 |
| Tatiana | SQL    |    87 |           87 |
+---------+--------+-------+--------------+

See Also

1.2.4.13 STD

Syntax

STD(expr)

Description

Returns the population standard deviation of expr. This is an extension to standard SQL. The standard SQL function STDDEV_POP() can be used instead.

It is an aggregate function, and so can be used with the GROUP BY clause.

From MariaDB 10.2.2, STD() can be used as a window function.

This function returns NULL if there were no matching rows.

Examples

As an aggregate function:

CREATE OR REPLACE TABLE stats (category VARCHAR(2), x INT);

INSERT INTO stats VALUES 
  ('a',1),('a',2),('a',3),
  ('b',11),('b',12),('b',20),('b',30),('b',60);

SELECT category, STDDEV_POP(x), STDDEV_SAMP(x), VAR_POP(x) 
  FROM stats GROUP BY category;
+----------+---------------+----------------+------------+
| category | STDDEV_POP(x) | STDDEV_SAMP(x) | VAR_POP(x) |
+----------+---------------+----------------+------------+
| a        |        0.8165 |         1.0000 |     0.6667 |
| b        |       18.0400 |        20.1693 |   325.4400 |
+----------+---------------+----------------+------------+

As a window function:

CREATE OR REPLACE TABLE student_test (name CHAR(10), test CHAR(10), score TINYINT);

INSERT INTO student_test VALUES 
    ('Chun', 'SQL', 75), ('Chun', 'Tuning', 73), 
    ('Esben', 'SQL', 43), ('Esben', 'Tuning', 31), 
    ('Kaolin', 'SQL', 56), ('Kaolin', 'Tuning', 88), 
    ('Tatiana', 'SQL', 87);

SELECT name, test, score, STDDEV_POP(score) 
  OVER (PARTITION BY test) AS stddev_results FROM student_test;
+---------+--------+-------+----------------+
| name    | test   | score | stddev_results |
+---------+--------+-------+----------------+
| Chun    | SQL    |    75 |        16.9466 |
| Chun    | Tuning |    73 |        24.1247 |
| Esben   | SQL    |    43 |        16.9466 |
| Esben   | Tuning |    31 |        24.1247 |
| Kaolin  | SQL    |    56 |        16.9466 |
| Kaolin  | Tuning |    88 |        24.1247 |
| Tatiana | SQL    |    87 |        16.9466 |
+---------+--------+-------+----------------+

See Also

1.2.4.14 STDDEV

Syntax

STDDEV(expr)

Contents

  1. Syntax
  2. Description
  3. Examples
  4. See Also

Description

Returns the population standard deviation of expr. This function is provided for compatibility with Oracle. The standard SQL function STDDEV_POP() can be used instead.

It is an aggregate function, and so can be used with the GROUP BY clause.

From MariaDB 10.2.2, STDDEV() can be used as a window function.

This function returns NULL if there were no matching rows.

Examples

As an aggregate function:

CREATE OR REPLACE TABLE stats (category VARCHAR(2), x INT);

INSERT INTO stats VALUES 
  ('a',1),('a',2),('a',3),
  ('b',11),('b',12),('b',20),('b',30),('b',60);

SELECT category, STDDEV_POP(x), STDDEV_SAMP(x), VAR_POP(x) 
  FROM stats GROUP BY category;
+----------+---------------+----------------+------------+
| category | STDDEV_POP(x) | STDDEV_SAMP(x) | VAR_POP(x) |
+----------+---------------+----------------+------------+
| a        |        0.8165 |         1.0000 |     0.6667 |
| b        |       18.0400 |        20.1693 |   325.4400 |
+----------+---------------+----------------+------------+

As a window function:

CREATE OR REPLACE TABLE student_test (name CHAR(10), test CHAR(10), score TINYINT);

INSERT INTO student_test VALUES 
    ('Chun', 'SQL', 75), ('Chun', 'Tuning', 73), 
    ('Esben', 'SQL', 43), ('Esben', 'Tuning', 31), 
    ('Kaolin', 'SQL', 56), ('Kaolin', 'Tuning', 88), 
    ('Tatiana', 'SQL', 87);

SELECT name, test, score, STDDEV_POP(score) 
  OVER (PARTITION BY test) AS stddev_results FROM student_test;
+---------+--------+-------+----------------+
| name    | test   | score | stddev_results |
+---------+--------+-------+----------------+
| Chun    | SQL    |    75 |        16.9466 |
| Chun    | Tuning |    73 |        24.1247 |
| Esben   | SQL    |    43 |        16.9466 |
| Esben   | Tuning |    31 |        24.1247 |
| Kaolin  | SQL    |    56 |        16.9466 |
| Kaolin  | Tuning |    88 |        24.1247 |
| Tatiana | SQL    |    87 |        16.9466 |
+---------+--------+-------+----------------+

See Also

1.2.4.15 STDDEV_POP

Syntax

STDDEV_POP(expr)

Contents

  1. Syntax
  2. Description
  3. Examples
  4. See Also

Description

Returns the population standard deviation of expr (the square root of VAR_POP()). You can also use STD() or STDDEV(), which are equivalent but not standard SQL.

It is an aggregate function, and so can be used with the GROUP BY clause.

From MariaDB 10.2.2, STDDEV_POP() can be used as a window function.

STDDEV_POP() returns NULL if there were no matching rows.

Examples

As an aggregate function:

CREATE OR REPLACE TABLE stats (category VARCHAR(2), x INT);

INSERT INTO stats VALUES 
  ('a',1),('a',2),('a',3),
  ('b',11),('b',12),('b',20),('b',30),('b',60);

SELECT category, STDDEV_POP(x), STDDEV_SAMP(x), VAR_POP(x) 
  FROM stats GROUP BY category;
+----------+---------------+----------------+------------+
| category | STDDEV_POP(x) | STDDEV_SAMP(x) | VAR_POP(x) |
+----------+---------------+----------------+------------+
| a        |        0.8165 |         1.0000 |     0.6667 |
| b        |       18.0400 |        20.1693 |   325.4400 |
+----------+---------------+----------------+------------+

As a window function:

CREATE OR REPLACE TABLE student_test (name CHAR(10), test CHAR(10), score TINYINT);

INSERT INTO student_test VALUES 
    ('Chun', 'SQL', 75), ('Chun', 'Tuning', 73), 
    ('Esben', 'SQL', 43), ('Esben', 'Tuning', 31), 
    ('Kaolin', 'SQL', 56), ('Kaolin', 'Tuning', 88), 
    ('Tatiana', 'SQL', 87);

SELECT name, test, score, STDDEV_POP(score) 
  OVER (PARTITION BY test) AS stddev_results FROM student_test;
+---------+--------+-------+----------------+
| name    | test   | score | stddev_results |
+---------+--------+-------+----------------+
| Chun    | SQL    |    75 |        16.9466 |
| Chun    | Tuning |    73 |        24.1247 |
| Esben   | SQL    |    43 |        16.9466 |
| Esben   | Tuning |    31 |        24.1247 |
| Kaolin  | SQL    |    56 |        16.9466 |
| Kaolin  | Tuning |    88 |        24.1247 |
| Tatiana | SQL    |    87 |        16.9466 |
+---------+--------+-------+----------------+

See Also

  • STD (equivalent, non-standard SQL)
  • STDDEV (equivalent, Oracle-compatible non-standard SQL)
  • VAR_POP (variance)
  • STDDEV_SAMP (sample standard deviation)

1.2.4.16 STDDEV_SAMP

Syntax

STDDEV_SAMP(expr)

Description

Returns the sample standard deviation of expr (the square root of VAR_SAMP()).

It is an aggregate function, and so can be used with the GROUP BY clause.

From MariaDB 10.2.2, STDDEV_SAMP() can be used as a window function.

STDDEV_SAMP() returns NULL if there were no matching rows.

1.2.4.17 SUM

Syntax

SUM([DISTINCT] expr)

Contents

  1. Syntax
  2. Description
  3. Examples
  4. See Also

Description

Returns the sum of expr. If the return set has no rows, SUM() returns NULL. The DISTINCT keyword can be used to sum only the distinct values of expr.

From MariaDB 10.2.0, SUM() can be used as a window function, although not with the DISTINCT specifier.

Examples

CREATE TABLE sales (sales_value INT);
INSERT INTO sales VALUES(10),(20),(20),(40);

SELECT SUM(sales_value) FROM sales;
+------------------+
| SUM(sales_value) |
+------------------+
|               90 |
+------------------+

SELECT SUM(DISTINCT(sales_value)) FROM sales;
+----------------------------+
| SUM(DISTINCT(sales_value)) |
+----------------------------+
|                         70 |
+----------------------------+

Commonly, SUM is used with a GROUP BY clause:

CREATE TABLE sales (name CHAR(10), month CHAR(10), units INT);

INSERT INTO sales VALUES 
  ('Chun', 'Jan', 75), ('Chun', 'Feb', 73),
  ('Esben', 'Jan', 43), ('Esben', 'Feb', 31),
  ('Kaolin', 'Jan', 56), ('Kaolin', 'Feb', 88),
  ('Tatiana', 'Jan', 87), ('Tatiana', 'Feb', 83);

SELECT name, SUM(units) FROM sales GROUP BY name;
+---------+------------+
| name    | SUM(units) |
+---------+------------+
| Chun    |        148 |
| Esben   |         74 |
| Kaolin  |        144 |
| Tatiana |        170 |
+---------+------------+

The GROUP BY clause is required when using an aggregate function along with regular column data, otherwise the result will be a mismatch, as in the following common type of mistake:

SELECT name,SUM(units) FROM sales
;+------+------------+
| name | SUM(units) |
+------+------------+
| Chun |        536 |
+------+------------+

As a window function:

CREATE OR REPLACE TABLE student_test (name CHAR(10), test CHAR(10), score TINYINT);
INSERT INTO student_test VALUES 
    ('Chun', 'SQL', 75), ('Chun', 'Tuning', 73), 
    ('Esben', 'SQL', 43), ('Esben', 'Tuning', 31), 
    ('Kaolin', 'SQL', 56), ('Kaolin', 'Tuning', 88), 
    ('Tatiana', 'SQL', 87);

SELECT name, test, score, SUM(score) OVER (PARTITION BY name) AS total_score FROM student_test;
+---------+--------+-------+-------------+
| name    | test   | score | total_score |
+---------+--------+-------+-------------+
| Chun    | SQL    |    75 |         148 |
| Chun    | Tuning |    73 |         148 |
| Esben   | SQL    |    43 |          74 |
| Esben   | Tuning |    31 |          74 |
| Kaolin  | SQL    |    56 |         144 |
| Kaolin  | Tuning |    88 |         144 |
| Tatiana | SQL    |    87 |          87 |
+---------+--------+-------+-------------+

See Also

1.2.4.18 VARIANCE

Syntax

VARIANCE(expr)

Contents

  1. Syntax
  2. Description
  3. Examples
  4. See Also

Description

Returns the population standard variance of expr. This is an extension to standard SQL. The standard SQL function VAR_POP() can be used instead.

Variance is calculated by

  • working out the mean for the set
  • for each number, subtracting the mean and squaring the result
  • calculate the average of the resulting differences

It is an aggregate function, and so can be used with the GROUP BY clause.

From MariaDB 10.2.2, VARIANCE() can be used as a window function.

VARIANCE() returns NULL if there were no matching rows.

Examples

CREATE TABLE v(i tinyint);

INSERT INTO v VALUES(101),(99);

SELECT VARIANCE(i) FROM v;
+-------------+
| VARIANCE(i) |
+-------------+
|      1.0000 |
+-------------+

INSERT INTO v VALUES(120),(80);

SELECT VARIANCE(i) FROM v;
+-------------+
| VARIANCE(i) |
+-------------+
|    200.5000 |
+-------------+

As an aggregate function:

CREATE OR REPLACE TABLE stats (category VARCHAR(2), x INT);

INSERT INTO stats VALUES 
  ('a',1),('a',2),('a',3),
  ('b',11),('b',12),('b',20),('b',30),('b',60);

SELECT category, STDDEV_POP(x), STDDEV_SAMP(x), VAR_POP(x) 
  FROM stats GROUP BY category;
+----------+---------------+----------------+------------+
| category | STDDEV_POP(x) | STDDEV_SAMP(x) | VAR_POP(x) |
+----------+---------------+----------------+------------+
| a        |        0.8165 |         1.0000 |     0.6667 |
| b        |       18.0400 |        20.1693 |   325.4400 |
+----------+---------------+----------------+------------+

As a window function:

CREATE OR REPLACE TABLE student_test (name CHAR(10), test CHAR(10), score TINYINT);

INSERT INTO student_test VALUES 
    ('Chun', 'SQL', 75), ('Chun', 'Tuning', 73), 
    ('Esben', 'SQL', 43), ('Esben', 'Tuning', 31), 
    ('Kaolin', 'SQL', 56), ('Kaolin', 'Tuning', 88), 
    ('Tatiana', 'SQL', 87);

SELECT name, test, score, VAR_POP(score) 
  OVER (PARTITION BY test) AS variance_results FROM student_test;
+---------+--------+-------+------------------+
| name    | test   | score | variance_results |
+---------+--------+-------+------------------+
| Chun    | SQL    |    75 |         287.1875 |
| Chun    | Tuning |    73 |         582.0000 |
| Esben   | SQL    |    43 |         287.1875 |
| Esben   | Tuning |    31 |         582.0000 |
| Kaolin  | SQL    |    56 |         287.1875 |
| Kaolin  | Tuning |    88 |         582.0000 |
| Tatiana | SQL    |    87 |         287.1875 |
+---------+--------+-------+------------------+

See Also

1.2.4.19 VAR_POP

Syntax

VAR_POP(expr)

Contents

  1. Syntax
  2. Description
  3. Examples
  4. See Also

Description

Returns the population standard variance of expr. It considers rows as the whole population, not as a sample, so it has the number of rows as the denominator. You can also use VARIANCE(), which is equivalent but is not standard SQL.

Variance is calculated by

  • working out the mean for the set
  • for each number, subtracting the mean and squaring the result
  • calculate the average of the resulting differences

It is an aggregate function, and so can be used with the GROUP BY clause.

From MariaDB 10.2.2, VAR_POP() can be used as a window function.

VAR_POP() returns NULL if there were no matching rows.

Examples

CREATE TABLE v(i tinyint);

INSERT INTO v VALUES(101),(99);

SELECT VAR_POP(i) FROM v;
+------------+
| VAR_POP(i) |
+------------+
|     1.0000 |
+------------+

INSERT INTO v VALUES(120),(80);

SELECT VAR_POP(i) FROM v;
+------------+
| VAR_POP(i) |
+------------+
|   200.5000 |
+------------+

As an aggregate function:

CREATE OR REPLACE TABLE stats (category VARCHAR(2), x INT);

INSERT INTO stats VALUES 
  ('a',1),('a',2),('a',3),
  ('b',11),('b',12),('b',20),('b',30),('b',60);

SELECT category, STDDEV_POP(x), STDDEV_SAMP(x), VAR_POP(x) 
  FROM stats GROUP BY category;
+----------+---------------+----------------+------------+
| category | STDDEV_POP(x) | STDDEV_SAMP(x) | VAR_POP(x) |
+----------+---------------+----------------+------------+
| a        |        0.8165 |         1.0000 |     0.6667 |
| b        |       18.0400 |        20.1693 |   325.4400 |
+----------+---------------+----------------+------------+

As a window function:

CREATE OR REPLACE TABLE student_test (name CHAR(10), test CHAR(10), score TINYINT);

INSERT INTO student_test VALUES 
    ('Chun', 'SQL', 75), ('Chun', 'Tuning', 73), 
    ('Esben', 'SQL', 43), ('Esben', 'Tuning', 31), 
    ('Kaolin', 'SQL', 56), ('Kaolin', 'Tuning', 88), 
    ('Tatiana', 'SQL', 87);

SELECT name, test, score, VAR_POP(score) 
  OVER (PARTITION BY test) AS variance_results FROM student_test;
+---------+--------+-------+------------------+
| name    | test   | score | variance_results |
+---------+--------+-------+------------------+
| Chun    | SQL    |    75 |         287.1875 |
| Esben   | SQL    |    43 |         287.1875 |
| Kaolin  | SQL    |    56 |         287.1875 |
| Tatiana | SQL    |    87 |         287.1875 |
| Chun    | Tuning |    73 |         582.0000 |
| Esben   | Tuning |    31 |         582.0000 |
| Kaolin  | Tuning |    88 |         582.0000 |
+---------+--------+-------+------------------+

See Also

1.2.4.20 VAR_SAMP

Syntax

VAR_SAMP(expr)

Contents

  1. Syntax
  2. Description
  3. Examples
  4. See Also

Description

Returns the sample variance of expr. That is, the denominator is the number of rows minus one.

It is an aggregate function, and so can be used with the GROUP BY clause.

From MariaDB 10.2.2, VAR_SAMP() can be used as a window function.

VAR_SAMP() returns NULL if there were no matching rows.

Examples

As an aggregate function:

CREATE OR REPLACE TABLE stats (category VARCHAR(2), x INT);

INSERT INTO stats VALUES 
  ('a',1),('a',2),('a',3),
  ('b',11),('b',12),('b',20),('b',30),('b',60);

SELECT category, STDDEV_POP(x), STDDEV_SAMP(x), VAR_POP(x) 
  FROM stats GROUP BY category;
+----------+---------------+----------------+------------+
| category | STDDEV_POP(x) | STDDEV_SAMP(x) | VAR_POP(x) |
+----------+---------------+----------------+------------+
| a        |        0.8165 |         1.0000 |     0.6667 |
| b        |       18.0400 |        20.1693 |   325.4400 |
+----------+---------------+----------------+------------+

As a window function:

CREATE OR REPLACE TABLE student_test (name CHAR(10), test CHAR(10), score TINYINT);

INSERT INTO student_test VALUES 
    ('Chun', 'SQL', 75), ('Chun', 'Tuning', 73), 
    ('Esben', 'SQL', 43), ('Esben', 'Tuning', 31), 
    ('Kaolin', 'SQL', 56), ('Kaolin', 'Tuning', 88), 
    ('Tatiana', 'SQL', 87);

SELECT name, test, score, VAR_SAMP(score) 
  OVER (PARTITION BY test) AS variance_results FROM student_test;
+---------+--------+-------+------------------+
| name    | test   | score | variance_results |
+---------+--------+-------+------------------+
| Chun    | SQL    |    75 |         382.9167 |
| Chun    | Tuning |    73 |         873.0000 |
| Esben   | SQL    |    43 |         382.9167 |
| Esben   | Tuning |    31 |         873.0000 |
| Kaolin  | SQL    |    56 |         382.9167 |
| Kaolin  | Tuning |    88 |         873.0000 |
| Tatiana | SQL    |    87 |         382.9167 |
+---------+--------+-------+------------------+

See Also

1.2.5 Numeric Functions

Functions dealing with numerals, including ABS, CEIL, DIV, EXP, PI, SIN, etc.

1.2.5.1 Addition Operator (+)

Syntax

+

Contents

  1. Syntax
  2. Description
  3. Examples
  4. See Also

Description

Addition.

If both operands are integers, the result is calculated with BIGINT precision. If either integer is unsigned, the result is also an unsigned integer.

For real or string operands, the operand with the highest precision determines the result precision.

Examples

SELECT 3+5;
+-----+
| 3+5 |
+-----+
|   8 |
+-----+

See Also

1.2.5.2 Subtraction Operator (-)

Syntax

-

Description

Subtraction. The operator is also used as the unary minus for changing sign.

If both operands are integers, the result is calculated with BIGINT precision. If either integer is unsigned, the result is also an unsigned integer, unless the NO_UNSIGNED_SUBTRACTION SQL_MODE is enabled, in which case the result is always signed.

For real or string operands, the operand with the highest precision determines the result precision.

Examples

SELECT 96-9;
+------+
| 96-9 |
+------+
|   87 |
+------+

SELECT 15-17;
+-------+
| 15-17 |
+-------+
|    -2 |
+-------+

SELECT 3.66 + 1.333;
+--------------+
| 3.66 + 1.333 |
+--------------+
|        4.993 |
+--------------+

Unary minus:

 SELECT - (3+5);
+---------+
| - (3+5) |
+---------+
|      -8 |
+---------+

See Also

1.2.5.3 Division Operator (/)

Syntax

/

Contents

  1. Syntax
  2. Description
  3. Examples
  4. See Also

Description

Division operator. Dividing by zero will return NULL. By default, returns four digits after the decimal. This is determined by the server system variable div_precision_increment which by default is four. It can be set from 0 to 30.

Dividing by zero returns NULL. If the ERROR_ON_DIVISION_BY_ZERO SQL_MODE is used (the default since MariaDB 10.2.4), a division by zero also produces a warning.

Examples

SELECT 4/5;
+--------+
| 4/5    |
+--------+
| 0.8000 |
+--------+

SELECT 300/(2-2);
+-----------+
| 300/(2-2) |
+-----------+
|      NULL |
+-----------+

SELECT 300/7;
+---------+
| 300/7   |
+---------+
| 42.8571 |
+---------+

Changing div_precision_increment for the session from the default of four to six:

SET div_precision_increment = 6;

SELECT 300/7;
+-----------+
| 300/7     |
+-----------+
| 42.857143 |
+-----------+

SELECT 300/7;
+-----------+
| 300/7     |
+-----------+
| 42.857143 |
+-----------+

See Also

1.2.5.4 Multiplication Operator (*)

Syntax

*

Contents

  1. Syntax
  2. Description
  3. Examples
  4. See Also

Description

Multiplication operator.

Examples

SELECT 7*6;
+-----+
| 7*6 |
+-----+
|  42 |
+-----+

SELECT 1234567890*9876543210;
+-----------------------+
| 1234567890*9876543210 |
+-----------------------+
|  -6253480962446024716 |
+-----------------------+

SELECT 18014398509481984*18014398509481984.0;
+---------------------------------------+
| 18014398509481984*18014398509481984.0 |
+---------------------------------------+
|   324518553658426726783156020576256.0 |
+---------------------------------------+

SELECT 18014398509481984*18014398509481984;
+-------------------------------------+
| 18014398509481984*18014398509481984 |
+-------------------------------------+
|                                   0 |
+-------------------------------------+

See Also

1.2.5.5 Modulo Operator (%)

Syntax

N % M

Description

Modulo operator. Returns the remainder of N divided by M. See also MOD.

Examples

SELECT 1042 % 50;
+-----------+
| 1042 % 50 |
+-----------+
|        42 |
+-----------+

1.2.5.6 DIV

Syntax

DIV

Description

Integer division. Similar to FLOOR(), but is safe with BIGINT values. Incorrect results may occur for non-integer operands that exceed BIGINT range.

If the ERROR_ON_DIVISION_BY_ZERO SQL_MODE is used, a division by zero produces an error. Otherwise, it returns NULL.

The remainder of a division can be obtained using the MOD operator.

Examples

SELECT 300 DIV 7;
+-----------+
| 300 DIV 7 |
+-----------+
|        42 |
+-----------+

SELECT 300 DIV 0;
+-----------+
| 300 DIV 0 |
+-----------+
|      NULL |
+-----------+

1.2.5.7 ABS

Syntax

ABS(X)

Contents

  1. Syntax
  2. Description
  3. Examples
  4. See Also

Description

Returns the absolute (non-negative) value of X. If X is not a number, it is converted to a numeric type.

Examples

SELECT ABS(42);
+---------+
| ABS(42) |
+---------+
|      42 |
+---------+

SELECT ABS(-42);
+----------+
| ABS(-42) |
+----------+
|       42 |
+----------+

SELECT ABS(DATE '1994-01-01');
+------------------------+
| ABS(DATE '1994-01-01') |
+------------------------+
|               19940101 |
+------------------------+

See Also

1.2.5.8 ACOS

Syntax

ACOS(X)

Contents

  1. Syntax
  2. Description
  3. Examples

Description

Returns the arc cosine of X, that is, the value whose cosine is X. Returns NULL if X is not in the range -1 to 1.

Examples

SELECT ACOS(1);
+---------+
| ACOS(1) |
+---------+
|       0 |
+---------+

SELECT ACOS(1.0001);
+--------------+
| ACOS(1.0001) |
+--------------+
|         NULL |
+--------------+

SELECT ACOS(0);
+-----------------+
| ACOS(0)         |
+-----------------+
| 1.5707963267949 |
+-----------------+

SELECT ACOS(0.234);
+------------------+
| ACOS(0.234)      |
+------------------+
| 1.33460644244679 |
+------------------+

1.2.5.9 ASIN

Syntax

ASIN(X)

Contents

  1. Syntax
  2. Description
  3. Examples

Description

Returns the arc sine of X, that is, the value whose sine is X. Returns NULL if X is not in the range -1 to 1.

Examples

SELECT ASIN(0.2);
+--------------------+
| ASIN(0.2)          |
+--------------------+
| 0.2013579207903308 |
+--------------------+

SELECT ASIN('foo');
+-------------+
| ASIN('foo') |
+-------------+
|           0 |
+-------------+

SHOW WARNINGS;
+---------+------+-----------------------------------------+
| Level   | Code | Message                                 |
+---------+------+-----------------------------------------+
| Warning | 1292 | Truncated incorrect DOUBLE value: 'foo' |
+---------+------+-----------------------------------------+

1.2.5.10 ATAN

Syntax

ATAN(X)

Contents

  1. Syntax
  2. Description
  3. Examples

Description

Returns the arc tangent of X, that is, the value whose tangent is X.

Examples

SELECT ATAN(2);
+--------------------+
| ATAN(2)            |
+--------------------+
| 1.1071487177940904 |
+--------------------+

SELECT ATAN(-2);
+---------------------+
| ATAN(-2)            |
+---------------------+
| -1.1071487177940904 |
+---------------------+

1.2.5.11 ATAN2

Syntax

ATAN(Y,X), ATAN2(Y,X)

Description

Returns the arc tangent of the two variables X and Y. It is similar to calculating the arc tangent of Y / X, except that the signs of both arguments are used to determine the quadrant of the result.

Examples

SELECT ATAN(-2,2);
+---------------------+
| ATAN(-2,2)          |
+---------------------+
| -0.7853981633974483 |
+---------------------+

SELECT ATAN2(PI(),0);
+--------------------+
| ATAN2(PI(),0)      |
+--------------------+
| 1.5707963267948966 |
+--------------------+

1.2.5.12 CEIL

Syntax

CEIL(X)

Description

CEIL() is a synonym for CEILING().

1.2.5.13 CEILING

Syntax

CEILING(X)

Description

Returns the smallest integer value not less than X.

Examples

SELECT CEILING(1.23);
+---------------+
| CEILING(1.23) |
+---------------+
|             2 |
+---------------+

SELECT CEILING(-1.23);
+----------------+
| CEILING(-1.23) |
+----------------+
|             -1 |
+----------------+

1.2.5.14 CONV

Syntax

CONV(N,from_base,to_base)

Description

Converts numbers between different number bases. Returns a string representation of the number N, converted from base from_base to base to_base.

Returns NULL if any argument is NULL, or if the second or third argument are not in the allowed range.

The argument N is interpreted as an integer, but may be specified as an integer or a string. The minimum base is 2 and the maximum base is 36. If to_base is a negative number, N is regarded as a signed number. Otherwise, N is treated as unsigned. CONV() works with 64-bit precision.

Some shortcuts for this function are also available: BIN(), OCT(), HEX(), UNHEX(). Also, MariaDB allows binary literal values and hexadecimal literal values.

Examples

SELECT CONV('a',16,2);
+----------------+
| CONV('a',16,2) |
+----------------+
| 1010           |
+----------------+

SELECT CONV('6E',18,8);
+-----------------+
| CONV('6E',18,8) |
+-----------------+
| 172             |
+-----------------+

SELECT CONV(-17,10,-18);
+------------------+
| CONV(-17,10,-18) |
+------------------+
| -H               |
+------------------+

SELECT CONV(12+'10'+'10'+0xa,10,10);
+------------------------------+
| CONV(12+'10'+'10'+0xa,10,10) |
+------------------------------+
| 42                           |
+------------------------------+

1.2.5.15 COS

Syntax

COS(X)

Description

Returns the cosine of X, where X is given in radians.

Examples

SELECT COS(PI());
+-----------+
| COS(PI()) |
+-----------+
|        -1 |
+-----------

1.2.5.16 COT

Syntax

COT(X)

Description

Returns the cotangent of X.

Examples

SELECT COT(42);
+--------------------+
| COT(42)            |
+--------------------+
| 0.4364167060752729 |
+--------------------+

SELECT COT(12);
+---------------------+
| COT(12)             |
+---------------------+
| -1.5726734063976893 |
+---------------------+

SELECT COT(0);
ERROR 1690 (22003): DOUBLE value is out of range in 'cot(0)'

1.2.5.17 CRC32

Syntax

<= MariaDB 10.7

CRC32(expr)

From MariaDB 10.8

CRC32([par,]expr)

Description

Computes a cyclic redundancy check (CRC) value and returns a 32-bit unsigned value. The result is NULL if the argument is NULL. The argument is expected to be a string and (if possible) is treated as one if it is not.

Uses the ISO 3309 polynomial that used by zlib and many others. MariaDB 10.8 introduced the CRC32C() function, which uses the alternate Castagnoli polynomia.

MariaDB starting with 10.8

Often, CRC is computed in pieces. To facilitate this, MariaDB 10.8.0 introduced an optional parameter: CRC32('MariaDB')=CRC32(CRC32('Maria'),'DB').

Examples

SELECT CRC32('MariaDB');
+------------------+
| CRC32('MariaDB') |
+------------------+
|       4227209140 |
+------------------+

SELECT CRC32('mariadb');
+------------------+
| CRC32('mariadb') |
+------------------+
|       2594253378 |
+------------------+

From MariaDB 10.8.0

SELECT CRC32(CRC32('Maria'),'DB');
+----------------------------+
| CRC32(CRC32('Maria'),'DB') |
+----------------------------+
|                 4227209140 |
+----------------------------+

See Also

1.2.5.18 CRC32C

MariaDB starting with 10.8

Introduced in MariaDB 10.8.0 to compute a cyclic redundancy check (CRC) value using the Castagnoli polynomial.

Syntax

CRC32C([par,]expr)

Description

MariaDB has always included a native unary function CRC32() that computes the CRC-32 of a string using the ISO 3309 polynomial that used by zlib and many others.

InnoDB and MyRocks use a different polynomial, which was implemented in SSE4.2 instructions that were introduced in the Intel Nehalem microarchitecture. This is commonly called CRC-32C (Castagnoli).

The CRC32C function uses the Castagnoli polynomial.

This allows SELECT…INTO DUMPFILE to be used for the creation of files with valid checksums, such as a logically empty InnoDB redo log file ib_logfile0 corresponding to a particular log sequence number.

The optional parameter allows the checksum to be computed in pieces: CRC32C('MariaDB')=CRC32C(CRC32C('Maria'),'DB').

Examples

SELECT CRC32C('MariaDB');
+-------------------+
| CRC32C('MariaDB') |
+-------------------+
|         809606978 |
+-------------------+

SELECT CRC32C(CRC32C('Maria'),'DB');
+------------------------------+
| CRC32C(CRC32C('Maria'),'DB') |
+------------------------------+
|                    809606978 |
+------------------------------+

1.2.5.19 DEGREES

Syntax

DEGREES(X)

Description

Returns the argument X, converted from radians to degrees.

This is the converse of the RADIANS() function.

Examples

SELECT DEGREES(PI());
+---------------+
| DEGREES(PI()) |
+---------------+
|           180 |
+---------------+

SELECT DEGREES(PI() / 2);
+-------------------+
| DEGREES(PI() / 2) |
+-------------------+
|                90 |
+-------------------+

SELECT DEGREES(45);
+-----------------+
| DEGREES(45)     |
+-----------------+
| 2578.3100780887 |
+-----------------+

1.2.5.20 EXP

Syntax

EXP(X)

Description

Returns the value of e (the base of natural logarithms) raised to the power of X. The inverse of this function is LOG() (using a single argument only) or LN().

If X is NULL, this function returns NULL.

Examples

SELECT EXP(2);
+------------------+
| EXP(2)           |
+------------------+
| 7.38905609893065 |
+------------------+

SELECT EXP(-2);
+--------------------+
| EXP(-2)            |
+--------------------+
| 0.1353352832366127 |
+--------------------+

SELECT EXP(0);
+--------+
| EXP(0) |
+--------+
|      1 |
+--------+

SELECT EXP(NULL);
+-----------+
| EXP(NULL) |
+-----------+
|      NULL |
+-----------+

1.2.5.21 FLOOR

Syntax

FLOOR(X)

Description

Returns the largest integer value not greater than X.

Examples

SELECT FLOOR(1.23);
+-------------+
| FLOOR(1.23) |
+-------------+
|           1 |
+-------------+

SELECT FLOOR(-1.23);
+--------------+
| FLOOR(-1.23) |
+--------------+
|           -2 |
+--------------+

1.2.5.22 GREATEST

1.2.5.23 LEAST

1.2.5.24 LN

Syntax

LN(X)

Description

Returns the natural logarithm of X; that is, the base-e logarithm of X. If X is less than or equal to 0, or NULL, then NULL is returned.

The inverse of this function is EXP().

Examples

SELECT LN(2);
+-------------------+
| LN(2)             |
+-------------------+
| 0.693147180559945 |
+-------------------+

SELECT LN(-2);
+--------+
| LN(-2) |
+--------+
|   NULL |
+--------+

1.2.5.25 LOG

Syntax

LOG(X), LOG(B,X)

Description

If called with one parameter, this function returns the natural logarithm of X. If X is less than or equal to 0, then NULL is returned.

If called with two parameters, it returns the logarithm of X to the base B. If B is <= 1 or X <= 0, the function returns NULL.

If any argument is NULL, the function returns NULL.

The inverse of this function (when called with a single argument) is the EXP() function.

Examples

LOG(X):

SELECT LOG(2);
+-------------------+
| LOG(2)            |
+-------------------+
| 0.693147180559945 |
+-------------------+

SELECT LOG(-2);
+---------+
| LOG(-2) |
+---------+
|    NULL |
+---------+

LOG(B,X)

SELECT LOG(2,16);
+-----------+
| LOG(2,16) |
+-----------+
|         4 |
+-----------+

SELECT LOG(3,27);
+-----------+
| LOG(3,27) |
+-----------+
|         3 |
+-----------+

SELECT LOG(3,1);
+----------+
| LOG(3,1) |
+----------+
|        0 |
+----------+

SELECT LOG(3,0);
+----------+
| LOG(3,0) |
+----------+
|     NULL |
+----------+

1.2.5.26 LOG10

Syntax

LOG10(X)

Description

Returns the base-10 logarithm of X.

Examples

SELECT LOG10(2);
+-------------------+
| LOG10(2)          |
+-------------------+
| 0.301029995663981 |
+-------------------+

SELECT LOG10(100);
+------------+
| LOG10(100) |
+------------+
|          2 |
+------------+

SELECT LOG10(-100);
+-------------+
| LOG10(-100) |
+-------------+
|        NULL |
+-------------+

1.2.5.27 LOG2

Syntax

LOG2(X)

Description

Returns the base-2 logarithm of X.

Examples

SELECT LOG2(4398046511104);
+---------------------+
| LOG2(4398046511104) |
+---------------------+
|                  42 |
+---------------------+

SELECT LOG2(65536);
+-------------+
| LOG2(65536) |
+-------------+
|          16 |
+-------------+

SELECT LOG2(-100);
+------------+
| LOG2(-100) |
+------------+
|       NULL |
+------------+

1.2.5.28 MOD

Syntax

MOD(N,M), N % M, N MOD M

Description

Modulo operation. Returns the remainder of N divided by M. See also Modulo Operator.

If the ERROR_ON_DIVISION_BY_ZERO SQL_MODE is used, any number modulus zero produces an error. Otherwise, it returns NULL.

The integer part of a division can be obtained using DIV.

Examples

SELECT 1042 % 50;
+-----------+
| 1042 % 50 |
+-----------+
|        42 |
+-----------+

SELECT MOD(234, 10);
+--------------+
| MOD(234, 10) |
+--------------+
|            4 |
+--------------+

SELECT 253 % 7;
+---------+
| 253 % 7 |
+---------+
|       1 |
+---------+

SELECT MOD(29,9);
+-----------+
| MOD(29,9) |
+-----------+
|         2 |
+-----------+

SELECT 29 MOD 9;
+----------+
| 29 MOD 9 |
+----------+
|        2 |
+----------+

1.2.5.29 OCT

Syntax

OCT(N)

Contents

  1. Syntax
  2. Description
  3. Examples
  4. See Also

Description

Returns a string representation of the octal value of N, where N is a longlong (BIGINT) number. This is equivalent to CONV(N,10,8). Returns NULL if N is NULL.

Examples

SELECT OCT(34);
+---------+
| OCT(34) |
+---------+
| 42      |
+---------+

SELECT OCT(12);
+---------+
| OCT(12) |
+---------+
| 14      |
+---------+

See Also

1.2.5.30 PI

Syntax

PI()

Description

Returns the value of π (pi). The default number of decimal places displayed is six, but MariaDB uses the full double-precision value internally.

Examples

SELECT PI();
+----------+
| PI()     |
+----------+
| 3.141593 |
+----------+

SELECT PI()+0.0000000000000000000000;
+-------------------------------+
| PI()+0.0000000000000000000000 |
+-------------------------------+
|      3.1415926535897931159980 |
+-------------------------------+

1.2.5.31 POW

Syntax

POW(X,Y)

Description

Returns the value of X raised to the power of Y.

POWER() is a synonym.

Examples

SELECT POW(2,3);
+----------+
| POW(2,3) |
+----------+
|        8 |
+----------+

SELECT POW(2,-2);
+-----------+
| POW(2,-2) |
+-----------+
|      0.25 |
+-----------+

1.2.5.32 POWER

Syntax

POWER(X,Y)

Description

This is a synonym for POW(), which returns the value of X raised to the power of Y.

1.2.5.33 RADIANS

Syntax

RADIANS(X)

Description

Returns the argument X, converted from degrees to radians. Note that π radians equals 180 degrees.

This is the converse of the DEGREES() function.

Examples

SELECT RADIANS(45);
+-------------------+
| RADIANS(45)       |
+-------------------+
| 0.785398163397448 |
+-------------------+

SELECT RADIANS(90);
+-----------------+
| RADIANS(90)     |
+-----------------+
| 1.5707963267949 |
+-----------------+

SELECT RADIANS(PI());
+--------------------+
| RADIANS(PI())      |
+--------------------+
| 0.0548311355616075 |
+--------------------+

SELECT RADIANS(180);
+------------------+
| RADIANS(180)     |
+------------------+
| 3.14159265358979 |
+------------------+

1.2.5.34 RAND

Contents

  1. Syntax
  2. Description
  3. Practical uses
  4. Examples
  5. See Also

Syntax

RAND(), RAND(N)

Description

Returns a random DOUBLE precision floating point value v in the range 0 <= v < 1.0. If a constant integer argument N is specified, it is used as the seed value, which produces a repeatable sequence of column values. In the example below, note that the sequences of values produced by RAND(3) is the same both places where it occurs.

In a WHERE clause, RAND() is evaluated each time the WHERE is executed.

Statements using the RAND() function are not safe for statement-based replication.

Practical uses

The expression to get a random integer from a given range is the following:

FLOOR(min_value + RAND() * (max_value - min_value +1))

RAND() is often used to read random rows from a table, as follows:

SELECT * FROM my_table ORDER BY RAND() LIMIT 10;

Note, however, that this technique should never be used on a large table as it will be extremely slow. MariaDB will read all rows in the table, generate a random value for each of them, order them, and finally will apply the LIMIT clause.

Examples

CREATE TABLE t (i INT);

INSERT INTO t VALUES(1),(2),(3);

SELECT i, RAND() FROM t;
+------+-------------------+
| i    | RAND()            |
+------+-------------------+
|    1 | 0.255651095188829 |
|    2 | 0.833920199269355 |
|    3 |  0.40264774151393 |
+------+-------------------+

SELECT i, RAND(3) FROM t;
+------+-------------------+
| i    | RAND(3)           |
+------+-------------------+
|    1 |  0.90576975597606 |
|    2 | 0.373079058130345 |
|    3 | 0.148086053457191 |
+------+-------------------+

SELECT i, RAND() FROM t;
+------+-------------------+
| i    | RAND()            |
+------+-------------------+
|    1 | 0.511478140495232 |
|    2 | 0.349447508668012 |
|    3 | 0.212803152588013 |
+------+-------------------+

Using the same seed, the same sequence will be returned:

SELECT i, RAND(3) FROM t;
+------+-------------------+
| i    | RAND(3)           |
+------+-------------------+
|    1 |  0.90576975597606 |
|    2 | 0.373079058130345 |
|    3 | 0.148086053457191 |
+------+-------------------+

Generating a random number from 5 to 15:

SELECT FLOOR(5 + (RAND() * 11));

See Also

1.2.5.35 ROUND

Syntax

ROUND(X), ROUND(X,D)

Description

Rounds the argument X to D decimal places. The rounding algorithm depends on the data type of X. D defaults to 0 if not specified. D can be negative to cause D digits left of the decimal point of the value X to become zero.

Examples

SELECT ROUND(-1.23);
+--------------+
| ROUND(-1.23) |
+--------------+
|           -1 |
+--------------+

SELECT ROUND(-1.58);
+--------------+
| ROUND(-1.58) |
+--------------+
|           -2 |
+--------------+

SELECT ROUND(1.58); 
+-------------+
| ROUND(1.58) |
+-------------+
|           2 |
+-------------+

SELECT ROUND(1.298, 1);
+-----------------+
| ROUND(1.298, 1) |
+-----------------+
|             1.3 |
+-----------------+

SELECT ROUND(1.298, 0);
+-----------------+
| ROUND(1.298, 0) |
+-----------------+
|               1 |
+-----------------+

SELECT ROUND(23.298, -1);
+-------------------+
| ROUND(23.298, -1) |
+-------------------+
|                20 |
+-------------------+

1.2.5.36 SIGN

Syntax

SIGN(X)

Description

Returns the sign of the argument as -1, 0, or 1, depending on whether X is negative, zero, or positive.

Examples

SELECT SIGN(-32);
+-----------+
| SIGN(-32) |
+-----------+
|        -1 |
+-----------+

SELECT SIGN(0);
+---------+
| SIGN(0) |
+---------+
|       0 |
+---------+

SELECT SIGN(234);
+-----------+
| SIGN(234) |
+-----------+
|         1 |
+-----------+

See Also

1.2.5.37 SIN

Syntax

SIN(X)

Description

Returns the sine of X, where X is given in radians.

Examples

SELECT SIN(1.5707963267948966);
+-------------------------+
| SIN(1.5707963267948966) |
+-------------------------+
|                       1 |
+-------------------------+

SELECT SIN(PI());
+----------------------+
| SIN(PI())            |
+----------------------+
| 1.22460635382238e-16 |
+----------------------+

SELECT ROUND(SIN(PI()));
+------------------+
| ROUND(SIN(PI())) |
+------------------+
|                0 |
+------------------+

1.2.5.38 SQRT

Syntax

SQRT(X)

Description

Returns the square root of X. If X is negative, NULL is returned.

Examples

SELECT SQRT(4);
+---------+
| SQRT(4) |
+---------+
|       2 |
+---------+

SELECT SQRT(20);
+------------------+
| SQRT(20)         |
+------------------+
| 4.47213595499958 |
+------------------+

SELECT SQRT(-16);
+-----------+
| SQRT(-16) |
+-----------+
|      NULL |
+-----------+

SELECT SQRT(1764);
+------------+
| SQRT(1764) |
+------------+
|         42 |
+------------+

1.2.5.39 TAN

Syntax

TAN(X)

Description

Returns the tangent of X, where X is given in radians.

Examples

SELECT TAN(0.7853981633974483);
+-------------------------+
| TAN(0.7853981633974483) |
+-------------------------+
|      0.9999999999999999 |
+-------------------------+

SELECT TAN(PI());
+-----------------------+
| TAN(PI())             |
+-----------------------+
| -1.22460635382238e-16 |
+-----------------------+

SELECT TAN(PI()+1);
+-----------------+
| TAN(PI()+1)     |
+-----------------+
| 1.5574077246549 |
+-----------------+

SELECT TAN(RADIANS(PI()));
+--------------------+
| TAN(RADIANS(PI())) |
+--------------------+
| 0.0548861508080033 |
+--------------------+

1.2.5.40 TRUNCATE

This page documents the TRUNCATE function. See TRUNCATE TABLE for the DDL statement.

Syntax

TRUNCATE(X,D)

Contents

  1. Syntax
  2. Description
  3. Examples
  4. See Also

Description

Returns the number X, truncated to D decimal places. If D is 0, the result has no decimal point or fractional part. D can be negative to cause D digits left of the decimal point of the value X to become zero.

Examples

SELECT TRUNCATE(1.223,1);
+-------------------+
| TRUNCATE(1.223,1) |
+-------------------+
|               1.2 |
+-------------------+

SELECT TRUNCATE(1.999,1);
+-------------------+
| TRUNCATE(1.999,1) |
+-------------------+
|               1.9 |
+-------------------+

SELECT TRUNCATE(1.999,0); 
+-------------------+
| TRUNCATE(1.999,0) |
+-------------------+
|                 1 |
+-------------------+

SELECT TRUNCATE(-1.999,1);
+--------------------+
| TRUNCATE(-1.999,1) |
+--------------------+
|               -1.9 |
+--------------------+

SELECT TRUNCATE(122,-2);
+------------------+
| TRUNCATE(122,-2) |
+------------------+
|              100 |
+------------------+

SELECT TRUNCATE(10.28*100,0);
+-----------------------+
| TRUNCATE(10.28*100,0) |
+-----------------------+
|                  1028 |
+-----------------------+

See Also

1.2.6 Control Flow Functions

Built-In functions for assessing data to determine what results to return.

There are 1 related questions.

1.2.6.1 CASE OPERATOR

Syntax

CASE value WHEN [compare_value] THEN result [WHEN [compare_value] THEN
result ...] [ELSE result] END

CASE WHEN [condition] THEN result [WHEN [condition] THEN result ...]
[ELSE result] END

Contents

  1. Syntax
  2. Description
  3. Examples

Description

The first version returns the result where value=compare_value. The second version returns the result for the first condition that is true. If there was no matching result value, the result after ELSE is returned, or NULL if there is no ELSE part.

There is also a CASE statement, which differs from the CASE operator described here.

Examples

SELECT CASE 1 WHEN 1 THEN 'one' WHEN 2 THEN 'two' ELSE 'more' END;
+------------------------------------------------------------+
| CASE 1 WHEN 1 THEN 'one' WHEN 2 THEN 'two' ELSE 'more' END |
+------------------------------------------------------------+
| one                                                        |
+------------------------------------------------------------+

SELECT CASE WHEN 1>0 THEN 'true' ELSE 'false' END;
+--------------------------------------------+
| CASE WHEN 1>0 THEN 'true' ELSE 'false' END |
+--------------------------------------------+
| true                                       |
+--------------------------------------------+


SELECT CASE BINARY 'B' WHEN 'a' THEN 1 WHEN 'b' THEN 2 END;
+-----------------------------------------------------+
| CASE BINARY 'B' WHEN 'a' THEN 1 WHEN 'b' THEN 2 END |
+-----------------------------------------------------+
|                                                NULL |
+-----------------------------------------------------+

1.2.6.2 DECODE

Syntax

DECODE(crypt_str,pass_str)

In Oracle mode from MariaDB 10.3.2:

DECODE(expr, search_expr, result_expr [, search_expr2, result_expr2 ...] [default_expr])

In all modes from MariaDB 10.3.2:

DECODE_ORACLE(expr, search_expr, result_expr [, search_expr2, result_expr2 ...] [default_expr])

Description

In the default mode, DECODE decrypts the encrypted string crypt_str using pass_str as the password. crypt_str should be a string returned from ENCODE(). The resulting string will be the original string only if pass_str is the same.

In Oracle mode from MariaDB 10.3.2, DECODE compares expr to the search expressions, in order. If it finds a match, the corresponding result expression is returned. If no matches are found, the default expression is returned, or NULL if no default is provided.

NULLs are treated as equivalent.

DECODE_ORACLE is a synonym for the Oracle-mode version of the function, and is available in all modes.

Examples

From MariaDB 10.3.2:

SELECT DECODE_ORACLE(2+1,3*1,'found1',3*2,'found2','default');
+--------------------------------------------------------+
| DECODE_ORACLE(2+1,3*1,'found1',3*2,'found2','default') |
+--------------------------------------------------------+
| found1                                                 |
+--------------------------------------------------------+

SELECT DECODE_ORACLE(2+4,3*1,'found1',3*2,'found2','default');
+--------------------------------------------------------+
| DECODE_ORACLE(2+4,3*1,'found1',3*2,'found2','default') |
+--------------------------------------------------------+
| found2                                                 |
+--------------------------------------------------------+

SELECT DECODE_ORACLE(2+2,3*1,'found1',3*2,'found2','default');
+--------------------------------------------------------+
| DECODE_ORACLE(2+2,3*1,'found1',3*2,'found2','default') |
+--------------------------------------------------------+
| default                                                |
+--------------------------------------------------------+

Nulls are treated as equivalent:

SELECT DECODE_ORACLE(NULL,NULL,'Nulls are equivalent','Nulls are not equivalent');
+----------------------------------------------------------------------------+
| DECODE_ORACLE(NULL,NULL,'Nulls are equivalent','Nulls are not equivalent') |
+----------------------------------------------------------------------------+
| Nulls are equivalent                                                       |
+----------------------------------------------------------------------------+

1.2.6.3 DECODE_ORACLE

MariaDB starting with 10.3.2

DECODE_ORACLE is a synonym for the Oracle mode version of the DECODE function, and is available in all modes.

1.2.6.4 IF Function

Syntax

IF(expr1,expr2,expr3)

Contents

  1. Syntax
  2. Description
  3. Examples
  4. See Also

Description

If expr1 is TRUE (expr1 <> 0 and expr1 <> NULL) then IF() returns expr2; otherwise it returns expr3. IF() returns a numeric or string value, depending on the context in which it is used.

Note: There is also an IF statement which differs from the IF() function described here.

Examples

SELECT IF(1>2,2,3);
+-------------+
| IF(1>2,2,3) |
+-------------+
|           3 |
+-------------+

SELECT IF(1<2,'yes','no');
+--------------------+
| IF(1<2,'yes','no') |
+--------------------+
| yes                |
+--------------------+

SELECT IF(STRCMP('test','test1'),'no','yes');
+---------------------------------------+
| IF(STRCMP('test','test1'),'no','yes') |
+---------------------------------------+
| no                                    |
+---------------------------------------+

See Also

There is also an IF statement, which differs from the IF() function described above.

1.2.6.5 IFNULL

Syntax

IFNULL(expr1,expr2)
NVL(expr1,expr2)

Contents

  1. Syntax
  2. Description
  3. Examples
  4. See Also

Description

If expr1 is not NULL, IFNULL() returns expr1; otherwise it returns expr2. IFNULL() returns a numeric or string value, depending on the context in which it is used.

From MariaDB 10.3, NVL() is an alias for IFNULL().

Examples

SELECT IFNULL(1,0); 
+-------------+
| IFNULL(1,0) |
+-------------+
|           1 |
+-------------+

SELECT IFNULL(NULL,10);
+-----------------+
| IFNULL(NULL,10) |
+-----------------+
|              10 |
+-----------------+

SELECT IFNULL(1/0,10);
+----------------+
| IFNULL(1/0,10) |
+----------------+
|        10.0000 |
+----------------+

SELECT IFNULL(1/0,'yes');
+-------------------+
| IFNULL(1/0,'yes') |
+-------------------+
| yes               |
+-------------------+

See Also

1.2.6.6 NULLIF

Syntax

NULLIF(expr1,expr2)

Contents

  1. Syntax
  2. Description
  3. Examples
  4. See Also

Description

Returns NULL if expr1 = expr2 is true, otherwise returns expr1. This is the same as CASE WHEN expr1 = expr2 THEN NULL ELSE expr1 END.

Examples

SELECT NULLIF(1,1);
+-------------+
| NULLIF(1,1) |
+-------------+
|        NULL |
+-------------+

SELECT NULLIF(1,2);
+-------------+
| NULLIF(1,2) |
+-------------+
|           1 |
+-------------+

See Also

1.2.6.7 NVL

MariaDB starting with 10.3

From MariaDB 10.3, NVL is a synonym for IFNULL.

1.2.6.8 NVL2

MariaDB starting with 10.3

The NLV2 function was introduced in MariaDB 10.3.0.

Syntax

NVL2(expr1,expr2,expr3)

Contents

  1. Syntax
  2. Description
  3. Examples
  4. See Also

Description

The NVL2 function returns a value based on whether a specified expression is NULL or not. If expr1 is not NULL, then NVL2 returns expr2. If expr1 is NULL, then NVL2 returns expr3.

Examples

SELECT NVL2(NULL,1,2);
+----------------+
| NVL2(NULL,1,2) |
+----------------+
|              2 |
+----------------+

SELECT NVL2('x',1,2);
+---------------+
| NVL2('x',1,2) |
+---------------+
|             1 |
+---------------+

See Also

1.2.7 Pseudo Columns

MariaDB has pseudo columns that can be used for different purposes.

1.2.7.1 _rowid

Syntax

_rowid

Description

The _rowid pseudo column is mapped to the primary key in the related table. This can be used as a replacement of the rowid pseudo column in other databases. Another usage is to simplify sql queries as one doesn't have to know the name of the primary key.

Examples

create table t1 (a int primary key, b varchar(80));
insert into t1 values (1,"one"),(2,"two");
select * from t1 where _rowid=1;

+---+------+
| a | b    |
+---+------+
| 1 | one  |
+---+------+

update t1 set b="three" where _rowid=2;
select * from t1 where _rowid>=1 and _rowid<=10;

+---+-------+
| a | b     |
+---+-------+
| 1 | one   |
| 2 | three |
+---+-------+

1.2.8 Secondary Functions

These are commonly used functions, but they are not primary functions.

1.2.8.1 Bit Functions and Operators

Operators for comparison and setting of values, and related functions.

1.2.8.1.1 Operator Precedence

1.2.8.1.2 &

Syntax

&

Description

Bitwise AND. Converts the values to binary and compares bits. Only if both the corresponding bits are 1 is the resulting bit also 1.

See also bitwise OR.

Examples

SELECT 2&1;
+-----+
| 2&1 |
+-----+
|   0 |
+-----+

SELECT 3&1;
+-----+
| 3&1 |
+-----+
|   1 |
+-----+

SELECT 29 & 15;
+---------+
| 29 & 15 |
+---------+
|      13 |
+---------+

1.2.8.1.3 <<

Syntax

value1 << value2

Description

Converts a longlong (BIGINT) number (value1) to binary and shifts value2 units to the left.

Examples

SELECT 1 << 2;
+--------+
| 1 << 2 |
+--------+
|      4 |
+--------+

1.2.8.1.4 >>

Syntax

value1 >> value2

Description

Converts a longlong (BIGINT) number (value1) to binary and shifts value2 units to the right.

Examples

SELECT 4 >> 2;
+--------+
| 4 >> 2 |
+--------+
|      1 |
+--------+

1.2.8.1.5 BIT_COUNT

Syntax

BIT_COUNT(N)

Description

Returns the number of bits that are set in the argument N.

Examples

SELECT BIT_COUNT(29), BIT_COUNT(b'101010');
+---------------+----------------------+
| BIT_COUNT(29) | BIT_COUNT(b'101010') |
+---------------+----------------------+
|             4 |                    3 |
+---------------+----------------------+

1.2.8.1.6 ^

Syntax

^

Description

Bitwise XOR. Converts the values to binary and compares bits. If one (and only one) of the corresponding bits is 1 is the resulting bit also 1.

Examples

SELECT 1 ^ 1;
+-------+
| 1 ^ 1 |
+-------+
|     0 |
+-------+

SELECT 1 ^ 0;
+-------+
| 1 ^ 0 |
+-------+
|     1 |
+-------+

SELECT 11 ^ 3;
+--------+
| 11 ^ 3 |
+--------+
|      8 |
+--------+

1.2.8.1.7 |

Syntax

|

Description

Bitwise OR. Converts the values to binary and compares bits. If either of the corresponding bits has a value of 1, the resulting bit is also 1.

See also bitwise AND.

Examples

SELECT 2|1;
+-----+
| 2|1 |
+-----+
|   3 |
+-----+

SELECT 29 | 15;
+---------+
| 29 | 15 |
+---------+
|      31 |
+---------+

1.2.8.1.8 ~

Syntax

~

Description

Bitwise NOT. Converts the value to 4 bytes binary and inverts all bits.

Examples

SELECT 3 & ~1;
+--------+
| 3 & ~1 |
+--------+
|      2 |
+--------+

SELECT 5 & ~1;
+--------+
| 5 & ~1 |
+--------+
|      4 |
+--------+

1.2.8.1.9 Parentheses

Parentheses are sometimes called precedence operators - this means that they can be used to change the other operator's precedence in an expression. The expressions that are written between parentheses are computed before the expressions that are written outside. Parentheses must always contain an expression (that is, they cannot be empty), and can be nested.

For example, the following expressions could return different results:

  • NOT a OR b
  • NOT (a OR b)

In the first case, NOT applies to a, so if a is FALSE or b is TRUE, the expression returns TRUE. In the second case, NOT applies to the result of a OR b, so if at least one of a or b is TRUE, the expression is TRUE.

When the precedence of operators is not intuitive, you can use parentheses to make it immediately clear for whoever reads the statement.

The precedence of the NOT operator can also be affected by the HIGH_NOT_PRECEDENCE SQL_MODE flag.

Other uses

Parentheses must always be used to enclose subqueries.

Parentheses can also be used in a JOIN statement between multiple tables to determine which tables must be joined first.

Also, parentheses are used to enclose the list of parameters to be passed to built-in functions, user-defined functions and stored routines. However, when no parameter is passed to a stored procedure, parentheses are optional. For builtin functions and user-defined functions, spaces are not allowed between the function name and the open parenthesis, unless the IGNORE_SPACE SQL_MODE is set. For stored routines (and for functions if IGNORE_SPACE is set) spaces are allowed before the open parenthesis, including tab characters and new line characters.

Syntax errors

If there are more open parentheses than closed parentheses, the error usually looks like this:

ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that
corresponds to your MariaDB server version for the right syntax to use near '' a
t line 1

Note the empty string.

If there are more closed parentheses than open parentheses, the error usually looks like this:

ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that
corresponds to your MariaDB server version for the right syntax to use near ')'
at line 1

Note the quoted closed parenthesis.

1.2.8.1.10 TRUE FALSE

Description

The constants TRUE and FALSE evaluate to 1 and 0, respectively. The constant names can be written in any lettercase.

Examples

SELECT TRUE, true, FALSE, false;
+------+------+-------+-------+
| TRUE | TRUE | FALSE | FALSE |
+------+------+-------+-------+
|    1 |    1 |     0 |     0 |
+------+------+-------+-------+

1.2.8.2 Encryption, Hashing and Compression Functions

Encryption, hashing and compression functions, such as ENCRYPT, DECRYPT, COMPRESS, PASSWORD etc.

There are 1 related questions.

1.2.8.2.1 AES_DECRYPT

Syntax

AES_DECRYPT(crypt_str,key_str)

Description

This function allows decryption of data using the official AES (Advanced Encryption Standard) algorithm. For more information, see the description of AES_ENCRYPT().

1.2.8.2.2 AES_ENCRYPT

Syntax

AES_ENCRYPT(str,key_str)

Description

AES_ENCRYPT() and AES_DECRYPT() allow encryption and decryption of data using the official AES (Advanced Encryption Standard) algorithm, previously known as "Rijndael." Encoding with a 128-bit key length is used, but you can extend it up to 256 bits by modifying the source. We chose 128 bits because it is much faster and it is secure enough for most purposes.

AES_ENCRYPT() encrypts a string str using the key key_str, and returns a binary string.

AES_DECRYPT() decrypts the encrypted string and returns the original string.

The input arguments may be any length. If either argument is NULL, the result of this function is also NULL.

Because AES is a block-level algorithm, padding is used to encode uneven length strings and so the result string length may be calculated using this formula:

16 x (trunc(string_length / 16) + 1)

If AES_DECRYPT() detects invalid data or incorrect padding, it returns NULL. However, it is possible for AES_DECRYPT() to return a non-NULL value (possibly garbage) if the input data or the key is invalid.

Examples

INSERT INTO t VALUES (AES_ENCRYPT('text',SHA2('password',512)));

1.2.8.2.3 COMPRESS

Syntax

COMPRESS(string_to_compress)

Description

Compresses a string and returns the result as a binary string. This function requires MariaDB to have been compiled with a compression library such as zlib. Otherwise, the return value is always NULL. The compressed string can be uncompressed with UNCOMPRESS().

The have_compress server system variable indicates whether a compression library is present.

Examples

SELECT LENGTH(COMPRESS(REPEAT('a',1000)));
+------------------------------------+
| LENGTH(COMPRESS(REPEAT('a',1000))) |
+------------------------------------+
|                                 21 |
+------------------------------------+

SELECT LENGTH(COMPRESS(''));
+----------------------+
| LENGTH(COMPRESS('')) |
+----------------------+
|                    0 |
+----------------------+

SELECT LENGTH(COMPRESS('a'));
+-----------------------+
| LENGTH(COMPRESS('a')) |
+-----------------------+
|                    13 |
+-----------------------+

SELECT LENGTH(COMPRESS(REPEAT('a',16)));
+----------------------------------+
| LENGTH(COMPRESS(REPEAT('a',16))) |
+----------------------------------+
|                               15 |
+----------------------------------+

1.2.8.2.4 DECODE

1.2.8.2.5 DES_DECRYPT

Syntax

DES_DECRYPT(crypt_str[,key_str])

Description

Decrypts a string encrypted with DES_ENCRYPT(). If an error occurs, this function returns NULL.

This function works only if MariaDB has been configured with TLS support.

If no key_str argument is given, DES_DECRYPT() examines the first byte of the encrypted string to determine the DES key number that was used to encrypt the original string, and then reads the key from the DES key file to decrypt the message. For this to work, the user must have the SUPER privilege. The key file can be specified with the --des-key-file server option.

If you pass this function a key_str argument, that string is used as the key for decrypting the message.

If the crypt_str argument does not appear to be an encrypted string, MariaDB returns the given crypt_str.

1.2.8.2.6 DES_ENCRYPT

Syntax

DES_ENCRYPT(str[,{key_num|key_str}])

Description

Encrypts the string with the given key using the Triple-DES algorithm.

This function works only if MariaDB has been configured with TLS support.

The encryption key to use is chosen based on the second argument to DES_ENCRYPT(), if one was given. With no argument, the first key from the DES key file is used. With a key_num argument, the given key number (0-9) from the DES key file is used. With a key_str argument, the given key string is used to encrypt str.

The key file can be specified with the --des-key-file server option.

The return string is a binary string where the first character is CHAR(128 | key_num). If an error occurs, DES_ENCRYPT() returns NULL.

The 128 is added to make it easier to recognize an encrypted key. If you use a string key, key_num is 127.

The string length for the result is given by this formula:

new_len = orig_len + (8 - (orig_len % 8)) + 1

Each line in the DES key file has the following format:

key_num des_key_str

Each key_num value must be a number in the range from 0 to 9. Lines in the file may be in any order. des_key_str is the string that is used to encrypt the message. There should be at least one space between the number and the key. The first key is the default key that is used if you do not specify any key argument to DES_ENCRYPT().

You can tell MariaDB to read new key values from the key file with the FLUSH DES_KEY_FILE statement. This requires the RELOAD privilege.

One benefit of having a set of default keys is that it gives applications a way to check for the existence of encrypted column values, without giving the end user the right to decrypt those values.

Examples

SELECT customer_address FROM customer_table 
   WHERE crypted_credit_card = DES_ENCRYPT('credit_card_number');

See Also

1.2.8.2.7 ENCODE

Syntax

ENCODE(str,pass_str)

Description

ENCODE is not considered cryptographically secure, and should not be used for password encryption.

Encrypt str using pass_str as the password. To decrypt the result, use DECODE().

The result is a binary string of the same length as str.

The strength of the encryption is based on how good the random generator is.

It is not recommended to rely on the encryption performed by the ENCODE function. Using a salt value (changed when a password is updated) will improve matters somewhat, but for storing passwords, consider a more cryptographically secure function, such as SHA2().

Examples

ENCODE('not so secret text', CONCAT('random_salt','password'))

1.2.8.2.8 ENCRYPT

Syntax

ENCRYPT(str[,salt])

Description

Encrypts a string using the Unix crypt() system call, returning an encrypted binary string. The salt argument should be a string with at least two characters or the returned result will be NULL. If no salt argument is given, a random value of sufficient length is used.

It is not recommended to use ENCRYPT() with utf16, utf32 or ucs2 multi-byte character sets because the crypt() system call expects a string terminated with a zero byte.

Note that the underlying crypt() system call may have some limitations, such as ignoring all but the first eight characters.

If the have_crypt system variable is set to NO (because the crypt() system call is not available), the ENCRYPT function will always return NULL.

Examples

SELECT ENCRYPT('encrypt me');
+-----------------------+
| ENCRYPT('encrypt me') |
+-----------------------+
| 4I5BsEx0lqTDk         |
+-----------------------+

1.2.8.2.9 MD5

Syntax

MD5(str)

Description

Calculates an MD5 128-bit checksum for the string.

The return value is a 32-hex digit string, and as of MariaDB 5.5, is a nonbinary string in the connection character set and collation, determined by the values of the character_set_connection and collation_connection system variables. Before 5.5, the return value was a binary string.

NULL is returned if the argument was NULL.

Examples

SELECT MD5('testing');
+----------------------------------+
| MD5('testing')                   |
+----------------------------------+
| ae2b1fca515949e5d54fb22b8ed95575 |
+----------------------------------+

1.2.8.2.10 OLD_PASSWORD

Syntax

OLD_PASSWORD(str)

Contents

  1. Syntax
  2. Description
  3. See Also

Description

OLD_PASSWORD() was added to MySQL when the implementation of PASSWORD() was changed to improve security. OLD_PASSWORD() returns the value of the old (pre-MySQL 4.1) implementation of PASSWORD() as a string, and is intended to permit you to reset passwords for any pre-4.1 clients that need to connect to a more recent MySQL server version, or any version of MariaDB, without locking them out.

As of MariaDB 5.5, the return value is a nonbinary string in the connection character set and collation, determined by the values of the character_set_connection and collation_connection system variables. Before 5.5, the return value was a binary string.

The return value is 16 bytes in length, or NULL if the argument was NULL.

See Also

1.2.8.2.11 PASSWORD

Syntax

PASSWORD(str)

Contents

  1. Syntax
  2. Description
  3. Examples
  4. See Also

Description

The PASSWORD() function is used for hashing passwords for use in authentication by the MariaDB server. It is not intended for use in other applications.

Calculates and returns a hashed password string from the plaintext password str. Returns an empty string (>= MariaDB 10.0.4) if the argument was NULL.

The return value is a nonbinary string in the connection character set and collation, determined by the values of the character_set_connection and collation_connection system variables.

This is the function that is used for hashing MariaDB passwords for storage in the Password column of the user table (see privileges), usually used with the SET PASSWORD statement. It is not intended for use in other applications.

Until MariaDB 10.3, the return value is 41-bytes in length, and the first character is always '*'. From MariaDB 10.4, the function takes into account the authentication plugin where applicable (A CREATE USER or SET PASSWORD statement). For example, when used in conjunction with a user authenticated by the ed25519 plugin, the statement will create a longer hash:

CREATE USER edtest@localhost IDENTIFIED VIA ed25519 USING PASSWORD('secret');

CREATE USER edtest2@localhost IDENTIFIED BY 'secret';

SELECT CONCAT(user, '@', host, ' => ', JSON_DETAILED(priv)) FROM mysql.global_priv
  WHERE user LIKE 'edtest%'\G
*************************** 1. row ***************************
CONCAT(user, '@', host, ' => ', JSON_DETAILED(priv)): edtest@localhost => {
...
    "plugin": "ed25519",
    "authentication_string": "ZIgUREUg5PVgQ6LskhXmO+eZLS0nC8be6HPjYWR4YJY",
...
}
*************************** 2. row ***************************
CONCAT(user, '@', host, ' => ', JSON_DETAILED(priv)): edtest2@localhost => {
...
    "plugin": "mysql_native_password",
    "authentication_string": "*14E65567ABDB5135D0CFD9A70B3032C179A49EE7",
...
}

The behavior of this function is affected by the value of the old_passwords system variable. If this is set to 1 (0 is default), MariaDB reverts to using the mysql_old_password authentication plugin by default for newly created users and passwords.

Examples

SELECT PASSWORD('notagoodpwd');
+-------------------------------------------+
| PASSWORD('notagoodpwd')                   |
+-------------------------------------------+
| *3A70EE9FC6594F88CE9E959CD51C5A1C002DC937 |
+-------------------------------------------+

SET PASSWORD FOR 'bob'@'%.loc.gov' = PASSWORD('newpass');

See Also

1.2.8.2.12 SHA1

Syntax

SHA1(str), SHA(str)

Description

Calculates an SHA-1 160-bit checksum for the string str, as described in RFC 3174 (Secure Hash Algorithm).

The value is returned as a string of 40 hex digits, or NULL if the argument was NULL. As of MariaDB 5.5, the return value is a nonbinary string in the connection character set and collation, determined by the values of the character_set_connection and collation_connection system variables. Before 5.5, the return value was a binary string.

Examples

SELECT SHA1('some boring text');
+------------------------------------------+
| SHA1('some boring text')                 |
+------------------------------------------+
| af969fc2085b1bb6d31e517d5c456def5cdd7093 |
+------------------------------------------+

1.2.8.2.13 SHA2

Syntax

SHA2(str,hash_len)

Description

Given a string str, calculates an SHA-2 checksum, which is considered more cryptographically secure than its SHA-1 equivalent. The SHA-2 family includes SHA-224, SHA-256, SHA-384, and SHA-512, and the hash_len must correspond to one of these, i.e. 224, 256, 384 or 512. 0 is equivalent to 256.

The return value is a nonbinary string in the connection character set and collation, determined by the values of the character_set_connection and collation_connection system variables.

NULL is returned if the hash length is not valid, or the string str is NULL.

SHA2 will only work if MariaDB was has been configured with TLS support.

Examples

SELECT SHA2('Maria',224);
+----------------------------------------------------------+
| SHA2('Maria',224)                                        |
+----------------------------------------------------------+
| 6cc67add32286412efcab9d0e1675a43a5c2ef3cec8879f81516ff83 |
+----------------------------------------------------------+

SELECT SHA2('Maria',256);
+------------------------------------------------------------------+
| SHA2('Maria',256)                                                |
+------------------------------------------------------------------+
| 9ff18ebe7449349f358e3af0b57cf7a032c1c6b2272cb2656ff85eb112232f16 |
+------------------------------------------------------------------+

SELECT SHA2('Maria',0);
+------------------------------------------------------------------+
| SHA2('Maria',0)                                                  |
+------------------------------------------------------------------+
| 9ff18ebe7449349f358e3af0b57cf7a032c1c6b2272cb2656ff85eb112232f16 |
+------------------------------------------------------------------+

1.2.8.2.14 UNCOMPRESS

1.2.8.2.15 UNCOMPRESSED_LENGTH

1.2.8.3 Information Functions

General information functions, including BENCHMARK, CHARSET, DATABASE, USER, VERSION, etc.

There are 1 related questions.

1.2.8.3.1 BENCHMARK

Syntax

BENCHMARK(count,expr)

Description

The BENCHMARK() function executes the expression expr repeatedly count times. It may be used to time how quickly MariaDB processes the expression. The result value is always 0. The intended use is from within the mysql client, which reports query execution times.

Examples

SELECT BENCHMARK(1000000,ENCODE('hello','goodbye'));
+----------------------------------------------+
| BENCHMARK(1000000,ENCODE('hello','goodbye')) |
+----------------------------------------------+
|                                            0 |
+----------------------------------------------+
1 row in set (0.21 sec)

1.2.8.3.2 BINLOG_GTID_POS

Syntax

BINLOG_GTID_POS(binlog_filename,binlog_offset)

Description

The BINLOG_GTID_POS() function takes as input an old-style binary log position in the form of a file name and a file offset. It looks up the position in the current binlog, and returns a string representation of the corresponding GTID position. If the position is not found in the current binlog, NULL is returned.

Examples

SELECT BINLOG_GTID_POS("master-bin.000001", 600);

See Also

1.2.8.3.3 CHARSET

Syntax

CHARSET(str)

Description

Returns the character set of the string argument. If str is not a string, it is considered as a binary string (so the function returns 'binary'). This applies to NULL, too. The return value is a string in the utf8 character set.

Examples

SELECT CHARSET('abc');
+----------------+
| CHARSET('abc') |
+----------------+
| latin1         |
+----------------+

SELECT CHARSET(CONVERT('abc' USING utf8));
+------------------------------------+
| CHARSET(CONVERT('abc' USING utf8)) |
+------------------------------------+
| utf8                               |
+------------------------------------+

SELECT CHARSET(USER());
+-----------------+
| CHARSET(USER()) |
+-----------------+
| utf8            |
+-----------------+

1.2.8.3.4 COERCIBILITY

Syntax

COERCIBILITY(str)

Description

Returns the collation coercibility value of the string argument. Coercibility defines what will be converted to what in case of collation conflict, with an expression with higher coercibility being converted to the collation of an expression with lower coercibility.

CoercibilityDescriptionExample
0ExplicitValue using a COLLATE clause
1No collationConcatenated strings using different collations
2ImplicitColumn value
3ConstantUSER() return value
4CoercibleLiteral string
5IgnorableNULL or derived from NULL

Examples

SELECT COERCIBILITY('abc' COLLATE latin1_swedish_ci);
+-----------------------------------------------+
| COERCIBILITY('abc' COLLATE latin1_swedish_ci) |
+-----------------------------------------------+
|                                             0 |
+-----------------------------------------------+

SELECT COERCIBILITY(USER());
+----------------------+
| COERCIBILITY(USER()) |
+----------------------+
|                    3 |
+----------------------+

SELECT COERCIBILITY('abc');
+---------------------+
| COERCIBILITY('abc') |
+---------------------+
|                   4 |
+---------------------+

1.2.8.3.5 COLLATION

Syntax

COLLATION(str)

Contents

  1. Syntax
  2. Description
  3. Examples
  4. See Also

Description

Returns the collation of the string argument. If str is not a string, it is considered as a binary string (so the function returns 'binary'). This applies to NULL, too. The return value is a string in the utf8 character set.

See Character Sets and Collations.

Examples

SELECT COLLATION('abc');
+-------------------+
| COLLATION('abc')  |
+-------------------+
| latin1_swedish_ci |
+-------------------+

SELECT COLLATION(_utf8'abc');
+-----------------------+
| COLLATION(_utf8'abc') |
+-----------------------+
| utf8_general_ci       |
+-----------------------+

See Also

1.2.8.3.6 CONNECTION_ID

Syntax

CONNECTION_ID()

Description

Returns the connection ID (thread ID) for the connection. Every thread (including events) has an ID that is unique among the set of currently connected clients.

Until MariaDB 10.3.1, returns MYSQL_TYPE_LONGLONG, or bigint(10), in all cases. From MariaDB 10.3.1, returns MYSQL_TYPE_LONG, or int(10), when the result would fit within 32-bits.

Examples

SELECT CONNECTION_ID();
+-----------------+
| CONNECTION_ID() |
+-----------------+
|               3 |
+-----------------+

See Also

1.2.8.3.7 CURRENT_ROLE

Syntax

CURRENT_ROLE, CURRENT_ROLE()

Description

Returns the current role name. This determines your access privileges. The return value is a string in the utf8 character set.

If there is no current role, NULL is returned.

The output of SELECT CURRENT_ROLE is equivalent to the contents of the ENABLED_ROLES Information Schema table.

USER() returns the combination of user and host used to login. CURRENT_USER() returns the account used to determine current connection's privileges.

Examples

SELECT CURRENT_ROLE;
+--------------+
| CURRENT_ROLE |
+--------------+
| NULL         |
+--------------+

SET ROLE staff;

SELECT CURRENT_ROLE;
+--------------+
| CURRENT_ROLE |
+--------------+
| staff        |
+--------------+

1.2.8.3.8 CURRENT_USER

Syntax

CURRENT_USER, CURRENT_USER()

Description

Returns the user name and host name combination for the MariaDB account that the server used to authenticate the current client. This account determines your access privileges. The return value is a string in the utf8 character set.

The value of CURRENT_USER() can differ from the value of USER(). CURRENT_ROLE() returns the current active role.

Examples

shell> mysql --user="anonymous"

select user(),current_user();
+---------------------+----------------+
| user()              | current_user() |
+---------------------+----------------+
| anonymous@localhost | @localhost     |
+---------------------+----------------+

When calling CURRENT_USER() in a stored procedure, it returns the owner of the stored procedure, as defined with DEFINER.

See Also

1.2.8.3.9 DATABASE

Syntax

DATABASE()

Description

Returns the default (current) database name as a string in the utf8 character set. If there is no default database, DATABASE() returns NULL. Within a stored routine, the default database is the database that the routine is associated with, which is not necessarily the same as the database that is the default in the calling context.

SCHEMA() is a synonym for DATABASE().

To select a default database, the USE statement can be run. Another way to set the default database is specifying its name at mysql command line client startup.

Examples

SELECT DATABASE();
+------------+
| DATABASE() |
+------------+
| NULL       |
+------------+

USE test;
Database changed

SELECT DATABASE();
+------------+
| DATABASE() |
+------------+
| test       |
+------------+

1.2.8.3.10 DECODE_HISTOGRAM

Syntax

DECODE_HISTOGRAM(hist_type,histogram)

Description

Returns a string of comma separated numeric values corresponding to a probability distribution represented by the histogram of type hist_type (SINGLE_PREC_HB or DOUBLE_PREC_HB). The hist_type and histogram would be commonly used from the mysql.column_stats table.

See Histogram Based Statistics for details.

Examples

CREATE TABLE origin (
  i INT UNSIGNED NOT NULL AUTO_INCREMENT PRIMARY KEY,
  v INT UNSIGNED NOT NULL
);

INSERT INTO origin(v) VALUES 
  (1),(2),(3),(4),(5),(10),(20),
  (30),(40),(50),(60),(70),(80),
  (90),(100),(200),(400),(800);

SET histogram_size=10,histogram_type=SINGLE_PREC_HB;

ANALYZE TABLE origin PERSISTENT FOR ALL;
+-------------+---------+----------+-----------------------------------------+
| Table       | Op      | Msg_type | Msg_text                                |
+-------------+---------+----------+-----------------------------------------+
| test.origin | analyze | status   | Engine-independent statistics collected |
| test.origin | analyze | status   | OK                                      |
+-------------+---------+----------+-----------------------------------------+

SELECT db_name,table_name,column_name,hist_type,
  hex(histogram),decode_histogram(hist_type,histogram) 
  FROM mysql.column_stats WHERE db_name='test' and table_name='origin';
+---------+------------+-------------+----------------+----------------------+-------------------------------------------------------------------+
| db_name | table_name | column_name | hist_type      | hex(histogram)       | decode_histogram(hist_type,histogram)                             |
+---------+------------+-------------+----------------+----------------------+-------------------------------------------------------------------+
| test    | origin     | i           | SINGLE_PREC_HB | 0F2D3C5A7887A5C3D2F0 | 0.059,0.118,0.059,0.118,0.118,0.059,0.118,0.118,0.059,0.118,0.059 |
| test    | origin     | v           | SINGLE_PREC_HB | 000001060C0F161C1F7F | 0.000,0.000,0.004,0.020,0.024,0.012,0.027,0.024,0.012,0.376,0.502 |
+---------+------------+-------------+----------------+----------------------+-------------------------------------------------------------------+

SET histogram_size=20,histogram_type=DOUBLE_PREC_HB;

ANALYZE TABLE origin PERSISTENT FOR ALL;
+-------------+---------+----------+-----------------------------------------+
| Table       | Op      | Msg_type | Msg_text                                |
+-------------+---------+----------+-----------------------------------------+
| test.origin | analyze | status   | Engine-independent statistics collected |
| test.origin | analyze | status   | OK                                      |
+-------------+---------+----------+-----------------------------------------+

SELECT db_name,table_name,column_name,
  hist_type,hex(histogram),decode_histogram(hist_type,histogram) 
  FROM mysql.column_stats WHERE db_name='test' and table_name='origin';
+---------+------------+-------------+----------------+------------------------------------------+-----------------------------------------------------------------------------------------+
| db_name | table_name | column_name | hist_type      | hex(histogram)                           | decode_histogram(hist_type,histogram)                                                   |
+---------+------------+-------------+----------------+------------------------------------------+-----------------------------------------------------------------------------------------+
| test    | origin     | i           | DOUBLE_PREC_HB | 0F0F2D2D3C3C5A5A78788787A5A5C3C3D2D2F0F0 | 0.05882,0.11765,0.05882,0.11765,0.11765,0.05882,0.11765,0.11765,0.05882,0.11765,0.05882 |
| test    | origin     | v           | DOUBLE_PREC_HB | 5200F600480116067E0CB30F1B16831CB81FD67F | 0.00125,0.00250,0.00125,0.01877,0.02502,0.01253,0.02502,0.02502,0.01253,0.37546,0.50063 |

1.2.8.3.11 DEFAULT

Syntax

DEFAULT(col_name)

Description

Returns the default value for a table column. If the column has no default value (and is not NULLABLE - NULLABLE fields have a NULL default), an error is returned.

For integer columns using AUTO_INCREMENT, 0 is returned.

When using DEFAULT as a value to set in an INSERT or UPDATE statement, you can use the bare keyword DEFAULT without the parentheses and argument to refer to the column in context. You can only use DEFAULT as a bare keyword if you are using it alone without a surrounding expression or function.

Examples

Select only non-default values for a column:

SELECT i FROM t WHERE i != DEFAULT(i);

Update values to be one greater than the default value:

UPDATE t SET i = DEFAULT(i)+1 WHERE i < 100;

When referring to the default value exactly in UPDATE or INSERT, you can omit the argument:

INSERT INTO t (i) VALUES (DEFAULT);
UPDATE t SET i = DEFAULT WHERE i < 100;

CREATE OR REPLACE TABLE t (
  i INT NOT NULL AUTO_INCREMENT, 
  j INT NOT NULL, 
  k INT DEFAULT 3, 
  l INT NOT NULL DEFAULT 4, 
  m INT, 
  PRIMARY KEY (i)
);

DESC t;
+-------+---------+------+-----+---------+----------------+
| Field | Type    | Null | Key | Default | Extra          |
+-------+---------+------+-----+---------+----------------+
| i     | int(11) | NO   | PRI | NULL    | auto_increment |
| j     | int(11) | NO   |     | NULL    |                |
| k     | int(11) | YES  |     | 3       |                |
| l     | int(11) | NO   |     | 4       |                |
| m     | int(11) | YES  |     | NULL    |                |
+-------+---------+------+-----+---------+----------------+

INSERT INTO t (j) VALUES (1);
INSERT INTO t (j,m) VALUES (2,2);
INSERT INTO t (j,l,m) VALUES (3,3,3);

SELECT * FROM t;
+---+---+------+---+------+
| i | j | k    | l | m    |
+---+---+------+---+------+
| 1 | 1 |    3 | 4 | NULL |
| 2 | 2 |    3 | 4 |    2 |
| 3 | 3 |    3 | 3 |    3 |
+---+---+------+---+------+

SELECT DEFAULT(i), DEFAULT(k), DEFAULT (l), DEFAULT(m) FROM t;
+------------+------------+-------------+------------+
| DEFAULT(i) | DEFAULT(k) | DEFAULT (l) | DEFAULT(m) |
+------------+------------+-------------+------------+
|          0 |          3 |           4 |       NULL |
|          0 |          3 |           4 |       NULL |
|          0 |          3 |           4 |       NULL |
+------------+------------+-------------+------------+

SELECT DEFAULT(i), DEFAULT(k), DEFAULT (l), DEFAULT(m), DEFAULT(j)  FROM t;
ERROR 1364 (HY000): Field 'j' doesn't have a default value

SELECT * FROM t WHERE i = DEFAULT(i);
Empty set (0.001 sec)

SELECT * FROM t WHERE j = DEFAULT(j);
ERROR 1364 (HY000): Field 'j' doesn't have a default value

SELECT * FROM t WHERE k = DEFAULT(k);
+---+---+------+---+------+
| i | j | k    | l | m    |
+---+---+------+---+------+
| 1 | 1 |    3 | 4 | NULL |
| 2 | 2 |    3 | 4 |    2 |
| 3 | 3 |    3 | 3 |    3 |
+---+---+------+---+------+

SELECT * FROM t WHERE l = DEFAULT(l);
+---+---+------+---+------+
| i | j | k    | l | m    |
+---+---+------+---+------+
| 1 | 1 |    3 | 4 | NULL |
| 2 | 2 |    3 | 4 |    2 |
+---+---+------+---+------+

SELECT * FROM t WHERE m = DEFAULT(m);
Empty set (0.001 sec)

SELECT * FROM t WHERE m <=> DEFAULT(m);
+---+---+------+---+------+
| i | j | k    | l | m    |
+---+---+------+---+------+
| 1 | 1 |    3 | 4 | NULL |
+---+---+------+---+------+

See Also

1.2.8.3.12 FOUND_ROWS

Syntax

FOUND_ROWS()

Description

A SELECT statement may include a LIMIT clause to restrict the number of rows the server returns to the client. In some cases, it is desirable to know how many rows the statement would have returned without the LIMIT, but without running the statement again. To obtain this row count, include a SQL_CALC_FOUND_ROWS option in the SELECT statement, and then invoke FOUND_ROWS() afterwards.

You can also use FOUND_ROWS() to obtain the number of rows returned by a SELECT which does not contain a LIMIT clause. In this case you don't need to use the SQL_CALC_FOUND_ROWS option. This can be useful for example in a stored procedure.

Also, this function works with some other statements which return a resultset, including SHOW, DESC and HELP. For DELETE ... RETURNING you should use ROW_COUNT(). It also works as a prepared statement, or after executing a prepared statement.

Statements which don't return any results don't affect FOUND_ROWS() - the previous value will still be returned.

Warning: When used after a CALL statement, this function returns the number of rows selected by the last query in the procedure, not by the whole procedure.

Statements using the FOUND_ROWS() function are not safe for replication.

Examples

SHOW ENGINES;
+--------------------+---------+----------------------------------------------------------------+--------------+------+------------+
| Engine             | Support | Comment                                                        | Transactions | XA   | Savepoints |
+--------------------+---------+----------------------------------------------------------------+--------------+------+------------+
| InnoDB             | DEFAULT | Supports transactions, row-level locking, and foreign keys     | YES          | YES  | YES        |
...
| SPHINX             | YES     | Sphinx storage engine                                          | NO           | NO   | NO         |
+--------------------+---------+----------------------------------------------------------------+--------------+------+------------+
11 rows in set (0.01 sec)

SELECT FOUND_ROWS();
+--------------+
| FOUND_ROWS() |
+--------------+
|           11 |
+--------------+

SELECT SQL_CALC_FOUND_ROWS * FROM tbl_name WHERE id > 100 LIMIT 10;

SELECT FOUND_ROWS();
+--------------+
| FOUND_ROWS() |
+--------------+
|           23 |
+--------------+

See Also

1.2.8.3.13 LAST_INSERT_ID

Syntax

LAST_INSERT_ID(), LAST_INSERT_ID(expr)

Contents

  1. Syntax
  2. Description
  3. Examples
  4. See Also

Description

LAST_INSERT_ID() (no arguments) returns the first automatically generated value successfully inserted for an AUTO_INCREMENT column as a result of the most recently executed INSERT statement. The value of LAST_INSERT_ID() remains unchanged if no rows are successfully inserted.

If one gives an argument to LAST_INSERT_ID(), then it will return the value of the expression and the next call to LAST_INSERT_ID() will return the same value. The value will also be sent to the client and can be accessed by the mysql_insert_id function.

For example, after inserting a row that generates an AUTO_INCREMENT value, you can get the value like this:

SELECT LAST_INSERT_ID();
+------------------+
| LAST_INSERT_ID() |
+------------------+
|                9 |
+------------------+

You can also use LAST_INSERT_ID() to delete the last inserted row:

DELETE FROM product WHERE id = LAST_INSERT_ID();

If no rows were successfully inserted, LAST_INSERT_ID() returns 0.

The value of LAST_INSERT_ID() will be consistent across all versions if all rows in the INSERT or UPDATE statement were successful.

The currently executing statement does not affect the value of LAST_INSERT_ID(). Suppose that you generate an AUTO_INCREMENT value with one statement, and then refer to LAST_INSERT_ID() in a multiple-row INSERT statement that inserts rows into a table with its own AUTO_INCREMENT column. The value of LAST_INSERT_ID() will remain stable in the second statement; its value for the second and later rows is not affected by the earlier row insertions. (However, if you mix references to LAST_INSERT_ID() and LAST_INSERT_ID(expr), the effect is undefined.)

If the previous statement returned an error, the value of LAST_INSERT_ID() is undefined. For transactional tables, if the statement is rolled back due to an error, the value of LAST_INSERT_ID() is left undefined. For manual ROLLBACK, the value of LAST_INSERT_ID() is not restored to that before the transaction; it remains as it was at the point of the ROLLBACK.

Within the body of a stored routine (procedure or function) or a trigger, the value of LAST_INSERT_ID() changes the same way as for statements executed outside the body of these kinds of objects. The effect of a stored routine or trigger upon the value of LAST_INSERT_ID() that is seen by following statements depends on the kind of routine:

  • If a stored procedure executes statements that change the value of LAST_INSERT_ID(), the new value will be seen by statements that follow the procedure call.
  • For stored functions and triggers that change the value, the value is restored when the function or trigger ends, so following statements will not see a changed value.

Examples

CREATE TABLE t (
  id INTEGER UNSIGNED AUTO_INCREMENT PRIMARY KEY, 
  f VARCHAR(1)) 
ENGINE = InnoDB;

INSERT INTO t(f) VALUES('a');

SELECT LAST_INSERT_ID();
+------------------+
| LAST_INSERT_ID() |
+------------------+
|                1 |
+------------------+

INSERT INTO t(f) VALUES('b');

INSERT INTO t(f) VALUES('c');

SELECT LAST_INSERT_ID();
+------------------+
| LAST_INSERT_ID() |
+------------------+
|                3 |
+------------------+

INSERT INTO t(f) VALUES('d'),('e');

SELECT LAST_INSERT_ID();
+------------------+
| LAST_INSERT_ID() |
+------------------+
|                4 |
+------------------+

SELECT * FROM t;
+----+------+
| id | f    |
+----+------+
|  1 | a    |
|  2 | b    |
|  3 | c    |
|  4 | d    |
|  5 | e    |
+----+------+

SELECT LAST_INSERT_ID(12);
+--------------------+
| LAST_INSERT_ID(12) |
+--------------------+
|                 12 |
+--------------------+

SELECT LAST_INSERT_ID();
+------------------+
| LAST_INSERT_ID() |
+------------------+
|               12 |
+------------------+

INSERT INTO t(f) VALUES('f');

SELECT LAST_INSERT_ID();
+------------------+
| LAST_INSERT_ID() |
+------------------+
|                6 |
+------------------+

SELECT * FROM t;
+----+------+
| id | f    |
+----+------+
|  1 | a    |
|  2 | b    |
|  3 | c    |
|  4 | d    |
|  5 | e    |
|  6 | f    |
+----+------+

SELECT LAST_INSERT_ID(12);
+--------------------+
| LAST_INSERT_ID(12) |
+--------------------+
|                 12 |
+--------------------+

INSERT INTO t(f) VALUES('g');

SELECT * FROM t;
+----+------+
| id | f    |
+----+------+
|  1 | a    |
|  2 | b    |
|  3 | c    |
|  4 | d    |
|  5 | e    |
|  6 | f    |
|  7 | g    |
+----+------+

See Also

1.2.8.3.14 LAST_VALUE

Syntax

LAST_VALUE(expr,[expr,...])

LAST_VALUE(expr) OVER (
  [ PARTITION BY partition_expression ]
  [ ORDER BY order_list ]
)

Contents

  1. Syntax
  2. Description
  3. Examples
  4. See Also

Description

LAST_VALUE() evaluates all expressions and returns the last.

This is useful together with setting user variables to a value with @var:=expr, for example when you want to get data of rows updated/deleted without having to do two queries against the table.

Since MariaDB 10.2.2, LAST_VALUE can be used as a window function.

Returns NULL if no last value exists.

Examples

CREATE TABLE t1 (a int, b int);
INSERT INTO t1 VALUES(1,10),(2,20);
DELETE FROM t1 WHERE a=1 AND last_value(@a:=a,@b:=b,1);
SELECT @a,@b;
+------+------+
| @a   | @b   |
+------+------+
|    1 |   10 |
+------+------+

As a window function:

CREATE TABLE t1 (
  pk int primary key,
  a int,
  b int,
  c char(10),
  d decimal(10, 3),
  e real
);

INSERT INTO t1 VALUES
( 1, 0, 1,    'one',    0.1,  0.001),
( 2, 0, 2,    'two',    0.2,  0.002),
( 3, 0, 3,    'three',  0.3,  0.003),
( 4, 1, 2,    'three',  0.4,  0.004),
( 5, 1, 1,    'two',    0.5,  0.005),
( 6, 1, 1,    'one',    0.6,  0.006),
( 7, 2, NULL, 'n_one',  0.5,  0.007),
( 8, 2, 1,    'n_two',  NULL, 0.008),
( 9, 2, 2,    NULL,     0.7,  0.009),
(10, 2, 0,    'n_four', 0.8,  0.010),
(11, 2, 10,   NULL,     0.9,  NULL);

SELECT pk, FIRST_VALUE(pk) OVER (ORDER BY pk) AS first_asc,
           LAST_VALUE(pk) OVER (ORDER BY pk) AS last_asc,
           FIRST_VALUE(pk) OVER (ORDER BY pk DESC) AS first_desc,
           LAST_VALUE(pk) OVER (ORDER BY pk DESC) AS last_desc
FROM t1
ORDER BY pk DESC;

+----+-----------+----------+------------+-----------+
| pk | first_asc | last_asc | first_desc | last_desc |
+----+-----------+----------+------------+-----------+
| 11 |         1 |       11 |         11 |        11 |
| 10 |         1 |       10 |         11 |        10 |
|  9 |         1 |        9 |         11 |         9 |
|  8 |         1 |        8 |         11 |         8 |
|  7 |         1 |        7 |         11 |         7 |
|  6 |         1 |        6 |         11 |         6 |
|  5 |         1 |        5 |         11 |         5 |
|  4 |         1 |        4 |         11 |         4 |
|  3 |         1 |        3 |         11 |         3 |
|  2 |         1 |        2 |         11 |         2 |
|  1 |         1 |        1 |         11 |         1 |
+----+-----------+----------+------------+-----------+

CREATE OR REPLACE TABLE t1 (i int);
INSERT INTO t1 VALUES (1),(2),(3),(4),(5),(6),(7),(8),(9),(10);

SELECT i,
  FIRST_VALUE(i) OVER (ORDER BY i ROWS BETWEEN CURRENT ROW and 1 FOLLOWING) AS f_1f,
  LAST_VALUE(i) OVER (ORDER BY i ROWS BETWEEN CURRENT ROW and 1 FOLLOWING) AS l_1f,
  FIRST_VALUE(i) OVER (ORDER BY i ROWS BETWEEN 1 PRECEDING AND 1 FOLLOWING) AS f_1p1f,
  LAST_VALUE(i) OVER (ORDER BY i ROWS BETWEEN 1 PRECEDING AND 1 FOLLOWING) AS f_1p1f,
  FIRST_VALUE(i) OVER (ORDER BY i ROWS BETWEEN 2 PRECEDING AND 1 PRECEDING) AS f_2p1p,
  LAST_VALUE(i) OVER (ORDER BY i ROWS BETWEEN 2 PRECEDING AND 1 PRECEDING) AS f_2p1p,
  FIRST_VALUE(i) OVER (ORDER BY i ROWS BETWEEN 1 FOLLOWING AND 2 FOLLOWING) AS f_1f2f,
  LAST_VALUE(i) OVER (ORDER BY i ROWS BETWEEN 1 FOLLOWING AND 2 FOLLOWING) AS f_1f2f
FROM t1;

+------+------+------+--------+--------+--------+--------+--------+--------+
| i    | f_1f | l_1f | f_1p1f | f_1p1f | f_2p1p | f_2p1p | f_1f2f | f_1f2f |
+------+------+------+--------+--------+--------+--------+--------+--------+
|    1 |    1 |    2 |      1 |      2 |   NULL |   NULL |      2 |      3 |
|    2 |    2 |    3 |      1 |      3 |      1 |      1 |      3 |      4 |
|    3 |    3 |    4 |      2 |      4 |      1 |      2 |      4 |      5 |
|    4 |    4 |    5 |      3 |      5 |      2 |      3 |      5 |      6 |
|    5 |    5 |    6 |      4 |      6 |      3 |      4 |      6 |      7 |
|    6 |    6 |    7 |      5 |      7 |      4 |      5 |      7 |      8 |
|    7 |    7 |    8 |      6 |      8 |      5 |      6 |      8 |      9 |
|    8 |    8 |    9 |      7 |      9 |      6 |      7 |      9 |     10 |
|    9 |    9 |   10 |      8 |     10 |      7 |      8 |     10 |     10 |
|   10 |   10 |   10 |      9 |     10 |      8 |      9 |   NULL |   NULL |
+------+------+------+--------+--------+--------+--------+--------+--------+

See Also

1.2.8.3.15 PROCEDURE ANALYSE

Syntax

analyse([max_elements[,max_memory]])

Description

This procedure is defined in the sql/sql_analyse.cc file. It examines the result from a query and returns an analysis of the results that suggests optimal data types for each column. To obtain this analysis, append PROCEDURE ANALYSE to the end of a SELECT statement:

SELECT ... FROM ... WHERE ... PROCEDURE ANALYSE([max_elements,[max_memory]])

For example:

SELECT col1, col2 FROM table1 PROCEDURE ANALYSE(10, 2000);

The results show some statistics for the values returned by the query, and propose an optimal data type for the columns. This can be helpful for checking your existing tables, or after importing new data. You may need to try different settings for the arguments so that PROCEDURE ANALYSE() does not suggest the ENUM data type when it is not appropriate.

The arguments are optional and are used as follows:

  • max_elements (default 256) is the maximum number of distinct values that analyse notices per column. This is used by analyse to check whether the optimal data type should be of type ENUM; if there are more than max_elements distinct values, then ENUM is not a suggested type.
  • max_memory (default 8192) is the maximum amount of memory that analyse should allocate per column while trying to find all distinct values.

See Also